This circuit is basically an oscillator which runs at around 100 MHz. The most important parts of the oscillator are the transistor Q1 and the tuned circuit, which comprises the inductor Ll and the variable capacitor CV1. When the battery is first connected, a brief surge of current flows from the collector to the emitter of Q1, causing an oscillating (i.e: alternating) current to flow back and forth between Ll and CV1. An oscillating voltage therefore appears at the junction of Ll and CV1. The frequency of the oscillation depends on the values of Ll and CV1, so that varying the value of CV1 tunes the oscillations to the exact frequency required.

To ensure proper DMX data transmission, always use proper DMX cables and a. When using The new Rayzor Q12 features (12) 15W Quad Color RGBW LEDs, high speed 16-bit resolution movement, color mixing, rainbow effect, a 7° to 14° field angle 24 May 2017 - Light Processor Q12 Manual. 1 Applies to shipping within Russia. Information about shipping policies for other countries can be found here: Payment and Delivery Information 2 In accordance with Kleinunternehmerstatus exception of §19 of the German Value Added Tax Law, we do not collect or display VAT. About Payment and Delivery Information.

The following is a simple yet powerful 4W FM transmitter which is tunable to 88-108MHz frequency. Connect to your ipod/computer, etc. When this was first made, I only had a 2N2219A on hand, which resulted in a lower RF output. I have since swapped out the transistor for a 2N3866 for full 4W output at around 15VDC supply. In order to achieve a high output level, you will need a well tuned antenna, and a large heatsink to dissipate the heat from T2 transistor. Transmitter was mounted in metal enclosure and works extremely well.

I finally got round to making my capacitor ESR tester this week after finding a nice simple 5 transistor version. Unfortunately, for me, the design was only SMD so, I decided to replicate his schematic in Eagle PCB using a through hole component design. I will not be going into much detail regarding ESR or Equivalent Series Resistance Meters as, there is already plenty of other sources of information on the subject. Yet, every tinkering knows capacitors are guilty of a lot of sins in electronics. Capacitors love to throw red herrings!

They can appear physically fine (no bulge), show good capacitance and hide in circuit, standing to attention like the Queens Guards hiding shorts and high resistance under their big hats. This is where the ESR tester can be a saviour, with the ability to test for 'out of specification' high resistance, within the capacitor.

They can also be used to test 'in circuit', without the need to remove every capacitor in the circuit. Solar energy is renewable, free, widely available and clean form of energy.

It is considered as a serious source of energy for many years because of the vast amounts of energy that is made freely available, if harnessed by modern technology. Many people are familiar with so-called photovoltaic cells, or solar panels, found on things like spacecraft, rooftops, and handheld calculators. The cells are made of semiconductor materials like those found in computer chips. When sunlight hits the cells, it knocks electrons loose from their atoms.

As the electrons flow through the cell, they generate electricity. In this project, we are building a power bank which harvests energy by using a solar panel. The energy gained by the solar panel is stored in a LiPo battery. Then the battery is used to supply a stable 5V which is used by USB gadgets. The power bank can also be charged by an external 5V source. The best thing for this power bank during day that you don’t need to remember to charge it. It charges itself by using the sunlight and you don’t come up with an empty bank.

Function generator with adjustable frequency from 0 Hz to over 400 kHz, adjustable amplitude, DC offset, duty, and of course the function selection – square, triangle, and sine. Generator based on good old ICL8038 integrated chip generator that gives pretty good shaped signals as for amateur purposes. This circuit has been designed a little differently than ICL’s note or other similar circuits are suggesting. I tested a bunch of different configurations with different peripherals and chosen the best – so to get good waveshape at 400kHz. I got rid of some of the elements, I added my own solutions. The two ICL chips that i have can oscillate around up to 420-430kHz, and practically we can get good waveforms up to that frequency. The proposed long range transmitter circuit really is very steady, harmonic free design which you can use with standard fm frequencies between 88 and 108 MHz.

This will likely encompass 5km spectrum (long range). It includes an extremely consistent oscillator for the reason that you employ LM7809 stabilizer that is a 9V stabilized power source for T1 transistor and for frequency realignment that may be reached by means of the 10K linear potentiometer. The output strength of this long range rf transmitter is approximately 1W. Transistor T1 is employed as an oscillator stage to present a small power steady frequency. To fine-tune the freq. Apply the 10k linear potentiometer this way: should you moderate, in the direction of ground, the freq.

Would probably decrease but when you fine-tune it in direction of + it would climb. Essentially the potentiometer is needed just as a flexible power source for the a pair of MV2019 varicap diodes. Both of these diodes function as a changeable capacitor whilst you regulate the pot. By tweaking the diode capacitance the L1 + diodes circuit renders a resonance circuit for T1.

Feel free to employ transistors similar to BF199, BF214 however be careful not to use BCs. At this point you don’t receive yet the long range fm wireless transmitter due to the fact that the electric power is fairly reduced, a maximum of 0.5 mW. After many years of employing this ugly and clumsy bench power supply, I decided it was time to build something better, smaller and nice looking.

It began as a variable power supply based on an LM338 5A voltage regulator and external power adapter. LM338's Data Sheet has several very helpful application notes and circuits. I chose one that illustrated variable output and included protection diodes.

Diodes are included to protect the regulator from damage in case the input is accidentally shorted to ground. This is a distinct possibility if using jumpers to attach it to the power supply. Also the output of station supply may be shorted if some other device fails. Without the diodes, if this happens, the capacitors will dump their charge back through the regulator. Since the current spike may be many amps, the regulator may fail. The diodes steer the current around the regulator and into ground, thereby protecting it from damage. With adequate input the LM338 makes a fabulous variable power supply.

This small supply is user friendly and fits nicely on my cluttered bench. Pen FM Transmitter bug projects have been very popular. The idea of being able to hide a transmitter in a pen is very appealing.

In an effort to reduce the size of this design, we have used surface-mount components. Firstly, the thought of using the coil in the tank circuit for transmitting RF was a little far fetched, but we used it as an example for those who were interested in experimenting with our circuits. Now we have gone back to a conventional antenna, the whip. The whip or straight-line antenna can be coiled, wound longitudinally or folded.

The way it is wound makes a big difference to its effectiveness, but when you are limited in space, you have to accept these limitations. Even though we have used this antenna set up in our previous pen bugs we have considerably improved the circuit to the point were it has low battery consumption, but high RF output. The size of this design has been reduced considerably by using surface-mount components. I found this FM transmitter circuit on the internet, it works very well and it is very simple to build, even for amateurs. I managed to squeeze all the parts on small 1.5 x 2 cm PCB. When using small wire antenna and 3V power the range is 50m.

The coil has 10 turns on a 3 mm diameter and is wound with 0.3 mm copper wire. The microphone is an electret type. Transmitting frequency is changed by stretching or compressing the coil. Furthermore, we can change the frequency by changing C2 capacitor (10pF capacitor with a frequency of about 88MHz, with 8.2pF 95Mhz and 6.8pF 104Mhz).

Further tuning to the correct frequency is done through the coil. Transmitter can be powered by 3V button battery.

This easy to build transmitter transmits high quality stereo sound from your MP3 player, computer, walkman or discman to any FM radio or car radio. The circuit is designed around the BA1404 single chip FM stereo transmitter from ROHM. The IC requires only a small number of external parts so it is well suited for hobbyist projects.

The chip features excellent frequency stability, low power consumption & good channel separation. The transmitting RF frequency can be set by adjusting the coil (Lx). This 2 turn coils is paired with a 39 pF capacitor (Cx) to give a frequency range from 87 MHz - 106 MHz. This FM VHF transmitter will output approximately 250mW of RF power using a 2N3866 output transistor and can operate between 75MHz and 146MHz. It utilities a variable high gain audio pre-amplifier which can detect voices 40 feet away using an electret microphone.

Using a NBFM scanner, ranges over 5KM have been achieved using a 48cm wire antenna. Coils are 22SWG 7mm air core. L1 and L2 should be 6 turns for 75MHz to 85MHz, 4 turns for 85MHz to 100MHz and 3 turns for 100 to 146MHz. For frequencies over 100MHz the Crystal will be higher than 20MHz hence the base emitter capacitor should be 47pF. L3 is a 4.7uH choke. It is ideal to tune up this circuit using a wave detector meter placed a few inches away from the transmitter. This is a high quality bench power supply with adjustable output voltage from 0 to 30V and adjustable output current from few miliamperes to 4 amperes.

Built-in electronic output current limiter that effectively controls the output current makes this power supply indispensable in the experimenters laboratory as it is possible to limit the current to the typical maximum that a circuit under test may require, and power it up then, without any fear that it may be damaged if something goes wrong. There is also a visual indication that the current limiter is in operation so that you can see at a glance that your circuit is exceeding or not its preset limits. The circuit is a simple 88-108 MHz VHF FM transmitter circuit.

It is basically a VHF Colpitts oscillator capable of transmitting sound or music to any standard FM receiver. The circuit is powered by 9V battery which makes it easily portable. It also has a capacitor microphone which picks up very weak sound signals.

The output frequency can be easily adjusted by potentiometer thanks to onboard MV2109 varicap diode and the frequency stability is quite good. The range of this transmitter is 100 meters. This simple circuit is based on BA1404 FM Transmitter, works with two AA batteries and can drive a 300W dipole antenna for improved range. There are many applications for an FM transmitter, particularly if it can broadcast in stereo. You can broadcast stereo signals from your CD player or any other source to an FM tuner or radio. The transmitter uses a single IC and a few other components.

It broadcasts on the FM band (88-108MHz) so that it can be received by any standard FM tuner or portable radio. This basic RF oscillator circuit is easy to build and the components are not critical. Most of them can be found in your junk parts box. The circuit operated with 9V DC power supply. The L1 antenna coil can be made by close winding 8 to 10 turns of 22 gauge insulted magnetic wire around 1/4 inch form such as a pencil.

You can experiment with the size of the coil and the number of turns to see how it affects the frequency and signal output of the oscillator. You should be able to pick up its signal with standard FM radio receiver. Signal In to any audio player through 0.1uF capacitor. This 7 Watt FM Transmitter was originally a 200mW unit, without the universal power stage added. Together with the power amp 2SC1971 / MRF237 / NTE342 it then became a 7W unit. I used this transmitter with a half-wave open-end dipole in a vertical position 50 feet above ground. Together with about 70 feet of coax, this transmitter delivered great audio at a distance of 10 miles.

Overall distance was 17 miles, but the audio signal was weak. I had no equipment, other than a watt meter to measure it's power and a digital FM tuner with a 5-LED Signal Strength Bargraph display to use as capturing the main oscillating frequency, which was right at 87.5 MHz. This circuit worked well for me, as I had experimented with it for nearly a year.

Of course, one would be better off with more equipment than I have had to capture the main oscillating frequency. That was, by far, one of the hardest things to capture. It was thru trial and error, with the FM tuner, in finally finding out how to grab the right frequency. When I finally did get used to find out where my 'main' frequency was, the unit performed extremely well.

Like I had said above, right at 10 miles, the unit was at its best giving clear audible audio into the speakers of my car. With the transmitting antenna at 50 feet above ground, I decided to see how well I could receive the transmitter signal from an overpass than is exactly 15 miles from the transmitter.

When I got to the top of the overpass in my car, the audio signal came in as 'clear as a bell'. I now understand what is meant when one says FM signal travels best in a line of sight.

Well, being on that overpass, if I had a strong telescope with me, I am sure I could see the 50 foot antenna in my oak tree. So with the overpass being right around 50 feet in height also, the transmitter surpassed my judgement call on its signal. I surrender this circuit to anyone who likes to experiment in things like this. This is one of my favorite radio builds just because of how simple it is and how well it is able to pick up a lot of FM radio stations. I have browsed the world in search of a one transistor FM receiver.

I have seen a couple but they were always attached to some sort of added device, such as another IC or another transistor for amplification in the receiver itself. Through my continued quest of searching for that too good to be true one transistor, I happened to run across a super-regenerative receiver, by Charles Kitchin, famous for his vast knowledge of regenerative designs. I printed out the schematic and made it. It turned out extremely well.

This is the most simple and cheap FM transmitter you can ever find. This circuit is really cool. This runs at very low voltage, by a CR2025 3V battery, current consumption is also low.And the total size of this FM transmitter (including battery, excluding antenna) is less than that of a matchbox. The circuit has a central RF oscillator NPN transistor BF494 (substitute: BF199). A coil takes care of the output frequency. It consists of 36SWG wire 2.5 turns only in 5mm diameter ferrite rod.

Keep the circuit as small as possible. Try to use no wires in the main functional area (transistor and coil). The input from the audio output of computer / PMP / mobile is given to the biased base of the transistor. The transistor gives a RF humming accordingly to the audio input, and the FM wave is spread by the external antenna. By using a standard TV antenna, the range of this transmitter can go up to 1KM radius, using small (15-20cm) Ariel, it can work up to around 50M range. This circuit is most suitable for miniature FM transmitter for use in computer, mobile etc to send music to home theater system without wires, and in homemade wireless walky-talkies.

This passive airband receiver is basically an amplified 'crystal radio' designed to receive nearby aircraft transmissions on 121 - 133 MHz frequency. Useful for listening to the pilot transmissions. The input tuned cct 'L' is a 2 turn loop, with 30mm diameter measured at 0.15uH on my LC Meter which intercepts RF directly as opposed to an LC cct fed with external aerial. Tuning capacitor is a 30pF Philips Beehive trimmer, with a short length of plastic tube glued - as a tuning shaft.

Capacitance runs from 28 to 7pF; which by formula gives a frequency range of 77 - 155MHz. Detector uses a biased 1N5711 (or similar) schottky diode with lowest forward-biassed voltage drop.

The two 10M resistors bias the detector diode and the op-amp input near mid-rail for better detector efficiency. LM358 dual op-amp draws less than 1 ma so the battery drain is minimal. Insertion of earphones plug completes supply circuit and acts as an on/off switch. 9V battery fits neatly inside a 30mm x 130mm long PVC tube. There are not many AM transmitters that are easier to build than this one because the inductor is not tapped and has a single winding. There is no need to wind the inductor as it is a readily available RF choke.

To make the circuit as small as possible, the conventional tuning capacitor has been dispensed with and fixed 220pF capacitors used instead. To tune it to a particular frequency, reduce one or both of the 220pF capacitors to raise the frequency or add capacitance in parallel to lower the frequency. Q1 is biased with a 1MO resistor to give a high input impedance and this allows the use of a crystal ear piece as a low cost microphone. This is a second revision of 50W LM3886 power amplifier that is used to power two bookshelf speakers. The sound produced by LM3886 chip is excellent so I decided to make another amplifier with it. The schematic is based on the schematic in the datasheet of the chip with minor changes. I removed the time delay capacitor connected to MUTE pin, because it's better to use separate DC protection schematic which has similar functionality.

I made the output inductance L1 by winding 15 turns of enameled wire around the resistor R7. The diameter of the wire must be minimum 0.4mm. The whole was wrapped with heat shrink. This is the most simple and cheap FM transmitter you can ever find. It's powered by CR2025 3V battery and current consumption is very low. The total size of this FM transmitter is less than that of a matchbox.

The circuit has a central RF oscillator NPN transistor BF494. A coil takes care of the output frequency. The coil consists of 36SWG wire 2.5 turns in 5mm diameter ferrite rod.

Keep the circuit as small as possible. By using a standard TV antenna, the range of this transmitter can go up to 1KM radius, using small 15-20cm wire, it can work up to around 50M range. This circuit is most suitable for miniature FM transmitter for use in computer, mobile etc to send music to home theater system without wires, and in homemade wireless walky-talkies.

When i was using operational amplifiers at school lab i wanted a function generator at home to play with and work on circuits with Op Amps for better understanding. So i found on the internet a free function generator circuit which uses the IC XR-2206, i printed the PCB with my UV exposure box, i bought an enclosure box, i put everything inside and here is the result. The function generator can generate Square, TTL, Sine and Triangle waveforms from 1Hz to 1Mhz with Voltage regulation to Square Sine and Triangle waveforms. This simple transmitter allows you to broadcast on FM radio band 87.5 - 108 MHz. It consists of a simple oscillator with silicon planar RF PNP transistor.

Directly to the oscillator an antenna is connected. Due to the large amplitude of RF voltage is sufficient antenna length of about 5-10 cm. I used insulated 7cm long copper wire 1mm diameter. I eliminated the tuning capacitor, which is usual for most bugs and miniature transmitters, because this greatly complicates the tuning. From my own experience I know that if you get closer to such capacitor, the operating frequency is changed. That's why I chose to use the voltage tuning using the Voltage Controlled Oscillator (VCO). Instead of tuning capacitor the varicap (capacitance diode) is used, which changes its capacity by changing the reverse DC voltage.

We can tune the operating frequency by changing the DC voltage using the trimmer P1. Varicap also provides frequency modulation. This is a small stereo FM transmitter.

Output can be tuned from 88 to 108Mhz and the transmitter can be battery powered or be used with presented low voltage power supply. Download Film 2014 Rizky Nazar Ganool. This circuit is based on the Rhom BA1404 datasheet. The maximum voltage should not exceed 3V. The IC can be driven from a 7805 Regulator with a couple of 1N4001 diodes to reduce the supply voltage to about 2.8 Volts.

RF output power is typically 500mW but range depends upon antenna coupling and efficiency, environment and size of antenna. A small telescopic whip has an expected range of at leaset 100 metres or more. Arduino Prototype is a spectacular development board fully compatible with Arduino Pro. It's breadboard compatible so it can be plugged into a breadboard for quick prototyping, and it has VCC & GND power pins available on both sides of PCB.

It's small, power efficient, yet customizable through onboard 2 x 7 perfboard that can be used for connecting various sensors and connectors. Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket. Board features 28-PIN DIP IC socket, user replaceable ATmega328 microcontroller flashed with Arduino bootloader, 16MHz crystal resonator and a reset switch. It has 14 digital input/output pins (0-13) of which 6 can be used as PWM outputs and 6 analog inputs (A0-A5). Arduino sketches are uploaded through any USB-Serial adapter connected to 6-PIN ICSP female header. Board is supplied by 2-5V voltage and may be powered by a battery such as Lithium Ion cell, two AA cells, external power supply or USB power adapter.

H-bridge is frequently used to control DC motors and stepper motors. When controlling a bipolar stepper motor, two full H-bridges are needed. There are many H-bridge ICs (like L298, MPC17529 and SN754410 which is a quad half H-bridge) for just that purpose. But if you are on a budget, you may want to consider building a dual H-bridge yourself. The following schematic shows a simple dual H-bridge using eight general purpose transistors (2N3904 and 2N3906). Given the maximum current of roughly 200mA, this circuit can be used to drive a small bipolar stepper motor operating between 5V and 12V, such as the stepper motors found in most floppy drives and CD / DVD drives. Presented FM transmitter is built around low power PLL transmitter and amplifier that boosts its signal all the way up to 6 Watts.

The signal is amplified by three RF stages of amplification. In the first and second stages of the transmitter one of the best driver transistors were used 2SC2053. You can use the other transistors but only up to 500mW of power. In the third stage 2SC1971 RF transistor was used to achieve 6W of power. For making any RF transmitter circuit at least two meters are necessary, one is frequency counter and the other is RF field strength meter for which the schematic is provided. The figure shows a schematic of an easy to build FM transmitter circuit. Mostly all FM transmitter circuits you will find online or in books require some kind of hand build inductor/coil and after building the transmitter you have to adjust that coil and trimmer capacitor a little to adjust the transmitter to transmit on your desired frequency.

If you are looking for an easy or simple FM transmitter circuit in which you don't have to make a coil with your hand then the circuit given here is ideal for you. The circuit is using a ready made 1uH inductor which can be purchased from an electronic components store. These inductors are mostly look like resistors. The circuit also does not require a trimmer capacitor, because we have used a fixed value of 39pF capacitor in the place of trimmer capacitor. We have already calculated and used the values of coil and capacitors of oscillator to broadcast on FM band, so you don't have to do any further adjustments and tuning after building the circuit.

The circuit can be operated with 9 to 12 volt DC. For antenna use a 12 inch wire or for maximum range use a 30 inch wire and make it vertical. Curious C-Beeper is a fun to build little probe that can be used to quickly detect the capacity of capacitors in pF nF range, test their stability with temperature changes, find broken wires, locate wires, trace wires on PCBs, and to locate live wires behind the walls without touching them. The circuit uses three transistors to make a most unusual capacitance beeper probe. When a capacitor is touched to the probe, the probe beeps at a frequency that varies with capacitance. The frequency change is so steep with capacitance that tiny capacitors may be precisely matched or an exact fixed value may be selected to replace a trimmer in a prototype. If the user has reasonably moist skin, simply holding one lead of the capacitor to be tested while touching the other lead to the probe is all that is necessary.

The user's body forms the other connection through the beeper's metal case. When the beeper is properly adjusted it draws only 10 uA with nothing touching the probe - no power switch is required.

This design is optimized for capacitors less than about 0.1 uF (100 nF). Large capacitors give a low frequency 'clicking' sound and small capacitors sound a tone that increases as the capacitance decreases. Many decades of frequency change occur over the beeper's range giving even the more tone-deaf among us sufficient change to discern slight differences in capacitance. The entire device is powered by two CR2032 lithium cells that fit into TicTac box. The use of power switch is unnecessary since the circuit consumes almost no power when not being used.

It's always handy to have a little amp kicking around to trace audio signals, test mics, CD tape and TV audio outputs. You know, something that doesn't weigh a lot and isn't clumsy. There are tons of uses for this little circuit. There are a couple of versions of this amplifier chip. Both are 8 pin DIP packages and the difference between the two are apparent by their part numbers. Either are suited for this circuit provided the supply voltage does not exceed the recommended 5 to 12 volt DC range. Power output can range from about 325 mW to about 750 mW within this supply range when using an 8 ohm speaker.

Power it with batteries or a small DC supply.why not solar cells or a little windmill generator? Here's how to build your own mini FM transmitter. It transmits FM waves so you could easily receive the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip. With this FM transmitter you could start your own mini FM station.

The circuit uses BC547 transistor to amplify the signal and then frequency modulate it. It uses 'frequency modulation' most commonly known as FM, the same principal to transmit audio signals captured by the microphone. This classic walkie talkie consists of both 27MHz transmitter and receiver all in one circuit.

Nearly all the components in the 4-transistor circuit are used for both transmitting and receiving making it simple to build and economical at the same time. The frequency-generating stage only needs 27MHz crystal to be removed and it becomes a receiver. Next is a three transistor audio amplifier with very high gain. The first transistor is a pre-amplifier and the next two are wired as a super-alpha pair, commonly called a Darlington pair to drive the speaker that is also used as a microphone.

The use of telescopic antenna will provide better reception and transmitting range. Use two identical walkie talkie circuits for two way communication. This is a VCO FM Transmitter. With good antenna (dipole placed outdoor and high) the transmitter has very good coverage range about 500 meters, the maximal coverage range is up to 4 km. To calibrate for maximum power connect 6 V / 0,1 light bulb to the output and use R1 to tune the right frequency, adjust L1 coil if necesary. Then use C14 and C15 to adjust the highest power (the highest light of the bulb). Then you can connect antenna and audio signal.

Adjust R2 until the audio sounds as loud as the other stations. This is a 1 Watt FM Transmitter amplifier with a good design that can be used to amplify a RF signal in the 88 – 108 MHz band. It is very sensitive if you use good RF power amplifier transistors, trimmers and coils. It has a power amplification factor of 9 to 12 dB (9 to 15 times).

At an input power of 0.1W the output will be 1W. You must choose T1 transistor depending on applied voltage.

If you have a 12V power supply then use transistors like: 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87. At 18 to 24V power supply you must use transistors like: 2N3866, 2N3553, KT922A, BLY91, BLX92A.

You may use 2N2219 at 12V but you will get an output power of 0.4W maximum. If you are starting to learn electronics variable bench power supply is the first thing you should build to power your projects. This simple power supply is built around the LM317/LM338/LM350 linear voltage regulator. The LM317 is one of the most popular voltage regulators on the market, and for good reason.

It is very simple to use and requires very few external components. LM317/LM338/LM350 regulators provide a stable and reliable output voltage adjustable between 1.25V and 37V. The short circuit protection is also built right in the voltage regulator. If you are looking into wireless communication between two Arduino modules, this project might be helpful. It uses low costs RF transmitter and receiver from Electronics-DIY.com to establish radio link between two Arduino boards up to 500 ft. Data can be transferred serially at the maximum rate of 2400 bps. The schematic shows how receiver and transmitter is hooked up to two different Arduino boards.

When wiring the receiver / transmitter you only need to give them power / ground and then a pin for the TX (serial transmit) or RX (serial receive) pin. I also wired a button to the Arduino doing the transmitting, and used the LED on pin 13 that is built into my Arduino boards on the receiver so I could test this setup. The test app just flashes LED on the receiving board when a button is pressed on the transmitting board. An adjustable power load is a piece of test equipment that often comes handy in the development of a certain electronics projects. For example, when you are building a power supply, it will come a time when you need to 'simulate' a load to see how well your design performs as the load varies. Adding power resistors to the output can sometimes do in a pinch, but often you will not have the right resistor value handy with the right power rating for the test.

This is where an adjustable electronic load comes handy. In this article, I'll show how you can build one using common components available to the electronics hobbyist. LM3886 is a high-fidelity audio power amplifier IC capable of delivering 68W of continuous power using 4 Ohm speakers. LM3886 provides excellent S/N ratio of 92dB and above as well as extremely low total harmonic distortion over the audio spectrum. LM3886 comes equipped with Self Peak Instantaneous Temperature Protection Circuitry (SPiKE) that makes it a class above other discrete and hybrid amplifiers. SPiKe Protection makes LM3886 amplifier safe against problems like over voltage, under voltage, overloads, shorts to the supplies, thermal runaway, and temperature peaks.

Here's FM transmitter for commercial FM band that provides 18 watts of power. Since the electronic diagram is too large we decided to divide it into two parts. The first part is the actual FM transmitter while the second part is 18W RF amplifier. The circuit should be built on an epoxy printed circuit board with the upper face components reserved for interconnecting tracks and the bottom solder to the ground plane. If powered by 14V and 2.5A transmitter outputs 15W of power, whereas 18V and 3.5A will provide 18W. BB110 variable capacitor connected to the collector of transistor BF199 adjusts the transmission frequency of the circuit.

2K2 potentiometer serves as fine tuning. Once the output frequency is adjusted amplifier variable capacitors must be adjusted for maximum output power one stage at a time. All adjustments must be made with 50 Ohm dummy load connected to the output of transmitter. As the world around us becomes more and more environmentally conscious, alternative energies such as solar power are becoming more and more popular.

The following solar charger is very simple and inexpensive to build and could be used to charge cellphones, tablets and other USB devices. 6V solar panel could be easily salvaged from outdoor garden lights. Solar charger uses REG113-5 efficient low dropout regulator that only loses 250mv of forward voltage.

Linear style regulators such as a LM7805 or LM317 type voltage regulators lose as much as 2-3V and can not be used in this application. Optionally you may also add four-resistor voltage divider to charge an iPhone or iPad. Here is a simple but powerful, stable and efficient schematic diagram for a 500W modified sine wave inverter circuit. Originally I used a 555 timer and a CD4017 decade counter to produce the modified sine wave, but then I thought a simple PIC micro controller with its internal clock would produce a stable 50Hz/60Hz frequency without the need for two ICs. As you can see its a very simple circuit. 220V transformer should be used for 220V voltage output. For 110V voltage output use transformer with 110V rating.

Veronica 1W FM transmitter is an easy to build transmitter. Veronica is also known for frequency stability, clean FM signal and uses no integrated circuit. The Veronica oscillator is actually formed from 2 oscillators which operates somewhere around 50 MHz in anti phase and the 2 signals are combined to form 100MHz FM radio signal. This kind of circuit design is stable and is amplified up to 1W by 2n4427 transistor.

Veronica transmitter is equipped with a mini-mixer and so you may forget an external mixer. This consist from T1 transistor which amplifies the microphone signal before it is combined with cd-player audio or PC signal. R1 and R2 are potentiometers (variable resistors) used to adjust the audio level. The component between R8 and C21 represents the oscillator wich generates radio signal. D1 is a varicap diode (like a variable capacitor or trimmer) controlled by audio signal. C12, C13 and L1 determines the frequency. Following 1W PLL transmitter exciter provides stable, low noise operation.

Transmitter uses a PLL frequency synthesizer built with MC145152 which covers the FM band in 100kHz steps. The VCO uses MV2109 varicap diode to automatically tune to selected frequency via SW1 dip switch. Output stage uses 2N4417 RF power transistor and provides 1W of RF power. With good antenna expected transmission range is 2km. Transmitter may be built on a double sided PCB, with top side copper left mostly undisturbed as a ground plane.

The copper is removed only around non-grounded pins. The ground connections can be soldered on the top side, so it’s not necessary to have plated-through holes. I like the idea of using LED Christmas lights because they look cool and consume very small amount of electricity, but the flicker drives me crazy! That's because they are powered directly from 110V AC voltage instead DC voltage which makes them flicker 60 times per second.

Here is a simple circuit that will completely eliminate LED Christmas lights flicker. The solution is to convert AC to DC voltage with resistor, rectifier diode and capacitor. Using 470 ohm - 1K resistor is very essential because it limits the current to 20mA and minimizes the voltage to about 80 volts. If we didn't use the resistor LEDs would be powered by over 50mA of current which is much more than what they need and that would definitely shorten their life. Note that lowering voltage does not reduce the brightness of the LEDs because when powered by DC voltage they are always on. Here is a very interesting and simple FM transmitter used to transmit audio in the wide range up to 100M using only one transistor. The entire circuit of FM transmitter is divided into three major stages oscillator, modulator and amplifier.

The transmitting frequency of 88-108 MHz is generated by adjusting VC1. The input audio generated by microphone is changed into electric signal and is given to base of transistor T1. Transistor T1 is used as oscillator which oscillates the frequency of 88-108 MHz. The oscillated frequency depends upon the value R2, C2, L2 and L3.

Transmitted audio from FM transmitter circuit can be received by standard FM receiver. This DAC is based on latest 32bit/384K PCM5102 DAC chip and DIR9001 from Texas Instruments. Sound quality produced by PCM5102 DAC is surprisingly good, very smooth and airy, with great dynamics and excellent soundstage. It features both S/PDIF and optical inputs connected to DIR9001 low jitter digital receiver.

PCM5102 uses a next generation architecture based on the PCM1792/4 TI's flagship DACs. It has 112dB SNR, with an integrated negative rail charge pump and line driver, so you don't need no opamps at the end or dual split supplies. Just a simple RC low pass filter is all that is needed. In addition, there's a fancy PLL involved that will autodetect I2S rate, configure the device, and generate it's own internal master clock so no need for external clock.

Entire DAC is powered by only 3.3V from 1117-33 regulator and consumes only 20mA of power. Although PCM5102 DAC can be powered by 4-12V DC voltage, it's recommended to power it from a single 3.7V LIPO battery to achieve the best performance.

This little project will demonstrate how you can use NEC IR protocol based TV, DVD or VCR remote control to control you home appliances like fan bulb or virtually anything. There are lots of projects out there to accomplish this task but i have to write my own code because of too many requests on IR infrared Remote Control Relay Board with PIC12F675 Microcontroller. There are a number of consumer Infrared protocols out there and they have been used for every single purpose possible, like PDA laptops and other consumer appliances. RC-5 & RC-6 by Phillips, RCA are few examples of consumer IR protocols.

This FM radio receiver circuit is very simple to build and is powered by just a single 1.5V battery cell. Receiver consists of a regenerative rf stage, TR1, followed by a two of three-stage audio amplifier, TR2 to TR4. In some areas 3 stages of audio amplification may not be necessary, in which case TR3 and its associated components can be omitted and the free end of capacitor C5 connected to the collector of TR2.

The critical part of the fm radio receiver is the first stage, TR1/VC1, where the wirings must be kept as short as possible. Coil L1 is formed by winding 8 turns of 1mm (20 swg) enamelled copper wire on a 6 mm diameter former, which is then removed. After that L1 should be stretched carefully and evenly to a length of about 13mm.

In this tutorial you will learn how to build a simple serial 16x2 LCD display that is controlled via Arduino board by only two wires. The magic behind is done by the PCF8574 chip, an I/O expander that communicates with the micro-controller by using I2C protocol. The PCF8574 is a quick and easy solution to extending and adding output/input ports to Arduino. The chip connects to a standard I2C bus and adds an additional 8 output ports.

A total of 8 LCD displays can be connected to the same two wire I2C bus with each board having a different address. This FM transmitter is about the simplest and most basic FM transmitter it is possible to build and have a useful transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will easily penetrate over three floors of an apartment building and go over 300 meters in the open air. The circuit we use is based on a proven Australian design.

It may be tuned anywhere in the FM band. Or it may be tuned outside the commercial M band for greater privacy. (Of course this means you must modify your FM radio to be able to receive the transmission or have a broad-band FM receiver.) The output power of this FM Tx is below the legal limits of many countries (eg, USA and Australia). However, some countries may ban ALL wireless transmissions without a license.

It is the responsibility of the builder to check the legal requirements for the operation of this circuit and to obey them. This portable FM Transmitter is easy to build.

I have used a pair of BC548 transistors in this circuit. Although not strictly RF transistors, they still give good range. Transmitter is powered by 9V battery. The coil L1 consists of 7 turns on a quarter inch plastic former with a tuning slug.

The tuning slug is adjusted to tune the transmitter. Actual range on my prototype tuned from 70MHz to around 120MHz. The aerial is a few inches of wire. Lengths of antenna wire should be 1 - 2 feet. The circuit is basically a radio frequency (RF) oscillator that operates around 70-120 MHz. Audio from audio jack is fed into the audio amplifier stage built around the first transistor. Output from the collector is fed into the base of the second transistor where it modulates the resonant frequency of the tank circuit by varying the junction capacitance of the transistor.

Junction capacitance is a function of the potential difference applied to the base of the transistor. The tank circuit is connected in a Colpitts oscillator circuit. This circuit provides an FM modulated signal with an output power of around 500mW. The input microphone pre-amp is built around a couple of 2N3904 transistors (Q1/Q2), and audio gain is limited by the 5k preset trim potentiometer. The oscillator is a colpitt stage, frequency of oscillation governed by the tank circuit made from two 5pF ceramic capacitors and the L2 inductor. The output stage operates as a 'Class D' amplifier, no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage.

The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage. Here's a portable FM broadcast radio receiver for reception of FM broadcast band based around FET transistor.

The topology is a classic grounded-gate FET VHF Hartley oscillator. The drain resonator inductance is centre-tapped with feedback to the source through a small capacitance.

By tapping down towards the cold-end of the coil the feedback isn't as critical as your usual source-drain capacitor feedback and it tends to be far less difficult to get to work across a broad range of frequencies. The RFC to an RC source circuit to implement self-quenching is very traditional for super-regenerative detectors. The quench gets frequency-modulated somewhat by the drain current, so it varies with signal strength and the recovered modulation, this is typical for self-quenched circuits. This article shows you how to build a very simple FM transmitter from thirteen components, a Printed Circuit Board (PCB) and a 9v battery. This project was designed to be mounted on a PCB, however you don’t have to.

You could construct the project on Vero board (strip board) or any other 0.1” pitch style of project board. If you just want to experiment with this circuit, you don’t even need a board; you can just solder the component s together and let the completed project just rest on the work top. No matter which style you choose, try to keep all component leads nice and short. You could also make the PCB much smaller than the one shown here which is approx. This is a good size to keep the unit small but nicer to work on for beginners. If you wanted to make one really small, you could use all SMT parts.

Park Assist circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. And D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall.

All distances mentioned before can vary, depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device sensitivity. Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc. ESR Meter is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors. Unlike other ESR Meters that only measure ESR value this one measures capacitor's ESR value as well as its capacitance all at the same time. Additionally, ESR Meter also tests and identifies PINs of all transistors such as Bipolar (NPN, PNP), FETs, MOSFETs (N-Channel, P-Channel, enhancement-mode and depletion-mode MOSFETs), Thyristors, SCRs and Triacs.

Tests and identifies PINs and voltage of diodes, dual diodes, varicap diodes (and their capacity), zener diodes (test voltage up to 5V) and LEDs. It measures resistance of resistors, power resistors, coils starting from just 0.1Ω up to 20MΩ.

If you want control the DVD or TV/AV system that located in your living room via the remote control when you sleeping in your Bedroom. This IR extender will achieve this for you. Basically, it works as a repeater that moves the IR signal to a different location. This is an improved IR remote control extender circuit. It has high noise immunity, is resistant to ambient and reflected light and has an increased range from remote control to the extender circuit of about 7 meters. It should work with any domestic apparatus that use 36-38kHz for the IR carrier frequency.

Modern power supplies are known as 'switching regulator power supplies.' In most switching supplies, the 110 volt AC input is first rectified by two diodes and filtered by a pair of capacitors. This creates two high- voltage sources; one positive and the other negative. A pair of transistors is then used to switch these high voltage supplies across the primary winding of a transformer. This switching action is very fast.

A typical switching speed is around 40,000 cycles per second or 40KHz. An integrated circuit is commonly used to control the transistors.

This IC not only controls the speed at which the transistors are switched, but also controls the amount of time that each transistor is energized. The output voltage of the power supply is determined by the 'on' time of the transistors. If the transistors are keep on for a longer period of time, the output voltage of the supply will rise, while shorter times lower the output voltage. This is known as 'pulse-width modulation.' Long range, very stable, harmonic free, FM transmitter circuit which can be used for FM frequencies between 88 and 108 MHz.

With good antenna transmitter can cover 5km range. It has a very stable oscillator because it uses LM7809 voltage regulator which is a 9V stabilized power supply for T1 transistor. Frequency adjustment is achieved by using the 10K linear potentiometer. The output power of this long range RF transmitter is around 1W but can be higher if you use transistors like KT920A, BLX65, BLY81, 2N3553, 2SC1970 or 2SC1971. Building two stage 40 Watt FM Transmitter Amplifier.

RF input power should be between 0.5 and 1 watt. Amplifier is powered by 28V power supply. The diagram shows a 2N3375 driving a 2N5643 but there are many other transistors that will work. I used these two transistors just because they were cheap at the time. If any of the variable capacitors are at full capacitance you can pad them out with a fixed ceramic capacitor of suitable value. Extra capacitance also might be needed on the base of the transistors (i had to add 3 100pF capacitors on the base of the 2N5643). The transistors are bolted to a piece of right angle aluminum which is fixed to the metal chassis to dissipate heat effectively.

Presented here is XR2206 function generator with multiple waveform selection and a frequency readout display. The diagram on the right shows the internal workings of the XR2206 in the form of a block diagram. Essentially the chip contains A VCO (voltage controller oscillator), wave shaper and buffer. The XR2206 frequency generator diagram frequency of the VCO is set with a capacitor and a resistor. The capacitor sets the frequency range whilst a variable resistor can be used to vary the frequency in the set range.

The frequency is defined by ƒ = 1/(RC). For a starting point for the design of the frequency generator I used the test circuit from the XR2206 datasheet. I built this on bread board and experimented with the timing resistor and capacitor and managed to get the frequency up to 4MHz. This is 150W FM transmitter amplifier for 88-108MHz band. The amplifier has two stages using BLF244 mosfet transistor for the first stage which requires 0.5 - 1Watt of RF input to get about 20watts to drive the final stage SD1407 which can push nearly 200 Watts on this design. This design is more or less broadband however I added two variable capacitors after each stage for optimum matching and power output. Make sure the trimmer and the capacitors after the final stage SD1407 are a high voltage types with at least 200V rating.

The power on this amplifier can be varied by adjusting the bias voltage using the white pot to the BLF244 mosfet. I added a zener diode onto the bias supply to protect the transistor from too much bias voltage. Here's how to build your own adjustable power supply based on LM317. The IC LM317 is so versatile that an almost unlimited number of different, small, high grade power supply circuits can be built using it.

The configurations can be introduced for different applications for upgrading an existing unit with features that would virtually make it indestructible. A few useful application circuits using IC LM317, collected from National Semiconductor's PDF datasheet are meticulously explained in this section with the help of the relevant circuit diagrams. All the circuits discussed below require an unregulated input voltage (max. 35 Volts) from any standard transformer/bridge/capacitor network. VHF FM Aircraft Receiver is a superregenative receiver developed for listening to FM transmitters but also tunes the aircraft band and the top portion of the FM broadcast band.

Receives both AM and FM (107mHz to 135 MHz). You can use this receiver with the any FM transmitter. The receiver is amazingly simple using only one transistor for the receiver section and one IC for the audio section. This circuit is a self-quenching regenerative RF receiver also known as a superregenerative receiver.

A superregenerative receiver performs two basic functions. First it feeds back a portion of the received signal from it’s output in phase to its input; and second a super audible quenching oscillator drives the amplifier through the point of oscillation and maximum sensitivity and then quenches the oscillation repeatedly. This keeps the feedback from driving the circuit into self-oscillation and allows the signal to be regenerated over and over again. In this version of the circuit, both functions are performed by the circuitry associated with Q1. The rest of the circuit, shown to the right of L3 in the schematic, comprise the audio amplification circuit and are centered on the LM386 Audio Amp IC. In this configuration the LM386 is set at a gain of 200 and feeds it’s output to a standard 1/8-inch diameter stereo phone jack.

The audio can then be heard by plugging any standard stereo headset into the jack. For months I’ve been looking for a simple FM BUG project, the ones online require inductors which you either have to acquire or build, if you don’t have a LCR meter it becomes rather hard to get the circuit working, specially if you’re a beginner without an oscilloscope! – Sometimes they don’t even tell you which inductance is required and you have to calculate an estimate, which is the main reason why many high frequency RF projects fail in the first place. This circuit on the other hand performs pretty well, even if you’re manipulating the board or touching the coax it will stay within the tuned frequency (unless you touch the transistor or timing capacitor!). The objective of this 3V FM Transmitter design is to provide a simple low-power transmitter solution for broadcasting audio from various audio sources. This transmitter transmits audio using small sensitive microphone.

Transmitter's frequency, as built is tunable via 15pF trimmer to the desired frequency, and the coil is embedded on the circuit board. This implementation is adapted to rebroadcast the output of a CD player, television receiver, or radio receiver. I use this transmitter so that I can move about the house and listen to my favorite programs without disturbing others. Within and the house, I find that I can get 50 to 100 meters away from the transmitter with the small pocket FM receiver I carry in my shirt pocket. This little broadcast FM transmitter has 500mW of RF output power and runs of 12-15V battery or power supply.

DC whose signal modulated by FM using four transistors. Transmitter includes four transmitter stages and draws around 100-150mA of current. Using the values of the circuit components, the frequency will be around 100 MHz but can be changed via coil.

Through the 5 pF capacitor and 10K ohm resistor, the modulation of audio signal is supplied to the tank circuit. The amount of modulation is being managed by the 1N4002, a general purpose rectifier diode. FM Transmitter's output stage is functioning as a class D amplifier where the output transistors act as a switch. This is high quality function generator system using the XR2206 chip. Waveform function generator capable of producing AM/FM modulated sine wave outputs find a wide range of applications in electrical measurement and laboratory instrumentation. This application note describes the design, construction and the performance of such a complete function generator system suitable for laboratory usage or hobbyist applications. The entire function generator is comprised of a single XR2206 monolithic IC and a limited number of passive circuit components.

It provides the engineer, student, or hobbyist with highly versatile laboratory instrument for waveform generation at a very small fraction of the cost of conventional function generators available today. This is very simple 1.2 - 36V adjustable bench power supply with 5A of output current. Max input voltage is 37V and output is adjustable via potentiometer between 1.2 up to 36 volts. TIP147 PNP darlington transistor boosts the current of LM317 from 100mA to 5A.

LM317 is the most useful and inexpensive adjustable regulator and for this circuit you can also use LM317L that can give 100mA, that's enough for transistor bias. D1 and D2 are protection diodes because when you turn the circuit off the output capacitors are discharging and can damage the transistor or regulator. 100nf capacitors are in parallel with electrolytic capacitors to remove high frequency noise because large value electrolytic have large ESR and ESL and can't remove high frequency noise. There are many miniature FM transmitter bug circuits online, this one is unique in that it runs completely on solar power.

No battery is required. As long as the sun is shining on the PV panel, the transmitter will transmit. The transmitter bug is useful as a 'remote ear', and can be used for anything from listening birds to surveillance work.

The mic preamp and oscillator circuits were borrowed from a common circuit found around the Internet, a regulated solar power supply and an RF amp that extends the range of transmitter and improves frequency stability were added. 12V dual power supply has symmetrical voltage output +12V and -12V with limited current to 100mA. It has been built to power three OPA627 opamps of Audio DAC I am building with PCM1792 & PCM1794 chips. Circuit has on the primary side only fuse. I couldn't find smaller than 50mA. We can connect power cord directly to the X1 connector or via power switch on the chassis. On the secondary side of transformer are connected two fuses 100mA and after them is bridge rectifier.

For filtering of rectified voltage there are C1 and C2. Next are positive and negative voltage regulators 78L12 and 79L12 with decoupling capacitors C3 to C6 close to regulators. Next are small filter capacitors and also signaling LEDs connected via resistors. Output voltages are connected to 3 pin connector. For signaling of presence of voltage is enough only one LED. We can also use 2 pin connectors for LED connecting.

The power output of many transmitter circuits are very low because no power amplifier stages are incorporated. The transmitter circuit described here has an extra RF power amplifier stage using 2N3866 RF power transistor after the oscillator stage to increase output power to 250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometers. Transmitter's oscillator is built around BF494 transistor T1. It is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to tune the frequency of the transmitter and to provide frequency modulation by audio signals.

The output of the oscillator is about 50 milliwatts. 2N3866 transistor T2 forms a VHF-class A power amplifier. It boosts the oscillator signal power four to five times. Thus 250mW of power is generated at the collector of transistor T2.

This is a simple 30V volt meter using PIC16F676 micro controller with 10-bit ADC (analog to digital converter) and three 7 segment LED displays. You can use this circuit to measure up to 30V DC. The possible applications are on bench power supply or as a digital panel meter in various systems. PIC16F676 is the heart and brain of this circuit. The internal adc of the mcu with a resistor network voltage divider is used to measure the input voltage.

Then 3 digits of comm anode 7 segment display is used to display final converted voltage. As you can see in the schematic the displays are multiplexed with each other. It means we switch on one display and put the corresponding digit on this while other two displays are off this cycle goes for each of the displays.

Lead Acid batteries have changed little since the 1880's although improvements in materials and manufacturing methods continue to bring improvements in energy density, life and reliability. All lead acid batteries consist of flat lead plates immersed in a pool of electrolyte. Regular water addition is required for most types of lead acid batteries although low-maintenance types come with excess electrolyte calculated to compensate for water loss during a normal lifetime. Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt batteries in series, or a single 12-volt battery. These batteries are constructed of several single cells connected in series each cell produces approximately 2.1 volts. A six-volt battery has three single cells, which when fully charged produce an output voltage of 6.3 volts. A twelve-volt battery has six single cells in series producing a fully charged output voltage of 12.6 volts.

BA1404 transmitter includes onboard RF amplifier for increased transmitting range. Operating voltage range is 1-3V, the circuit contains FM stereo mixer, 38KHZ oscillator, FM modulator and high-frequency amplifier monolithic integrated circuit. As the 'electronic newspaper' BBS there are many users requiring detailed information on the FM stereo transmitter, so I re-collect the relevant information on the simple discrete, merge, integrated FM stereo transmitter experiment, that BA1404 with μpc1651 mix of the most easy to make and debug, and very high frequency stability (relative to the previous circuit BA1404), transmission power is increased by UPC1651RF amplifier. Here is a simple USB FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio by connecting it to an USB port. The circuit use no coils that have to be wound. This USB transmitter can be used to listen to your own music throughout your home.

To keep the fm transmitter circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606. This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency.

The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency. Single Ended Valve Triode Amplifier has not same tone with Push Psu Amplifier. Over 90% of Amplifiers are push pull, and push pull amplifier does not 2nd harmonic and off course does not get 2nd 4th, 6th harmonic vs SE has 2nd, 4th, 6th harmonic. Push pull has minor distortion than SE Amplifier.2nd harmonic is make good tone for Music.not too much and not less than.feel good sound get from Single Ended Amplifiers with high efficiency speakers from 88dB/m to 100dB/m. I means Single Ended Amplifier is almost Single Ended Triode Amplifier.or Penthode but wired Triode.

Tone is Different.good for Jazz and small room Classic. The 1 watt 20 meter QRP transmitter with VXO. This is a nice QRP transmitter that can be used in combination of one of the simple receivers. Normally these designs have only two transistors: one is the X-tal oscillator and the second the final amplifier. A good example is my first QRP rig that is also described somewhere on this site. Here the VXO (Variabele X-tal Oscillator) has a tuning range of 16 kHz. This VXO is buffered with an extra driver stage for a better frequency stability and a varicap diode is used instead of a variabele capacitor.

An extra transistor is added for keying the transmitter with a low keying current. What you can do with such a simple 1 watt QRP power transmitter. This is a real low power transmitter, so do not expect that you can do everything with it but.

When conditions are normal, you can easily make many QSO's during one afternoon with stations with distances upto 2000 km with a simple inverted V wire dipole antenna! From Europe, I did even make QSO's across the Ocean!

This PLL transmitter is controlled and the frequency is very stable and can be programmed digitally. Transmitter will work 88-108 MHz and output power up to 500mW. With a small change can set the frequency of 50-150 MHz. The output power is often set to several watts with transistors. So therefore I decided to build a simple transmitter with great performances. The frequency of this transmitter can easily be changed by software and space / compress air coil.

This transmitter is the oscillator colpitts. Oscillator is a VCO (voltage controlled oscillator) which is set by the PLL circuit and PIC micro controller. This oscillator is called the Colpitts oscillator and voltage controlled to achieve the FM (frequency modulation) and PLL control. Field strength meter is extremely useful when working with RF devices. It can be used to quickly diagnose whether a transmitter circuit is working, and can be used to detect RF signals in the environment. The simplest field strength meter could be built with a tuned LC circuit and a germanium diode, just like the way of a building a crystal radio except replacing the ear piece with a high sensitivity current meter.

While this approach fits the needs of most simple applications, it has a pretty narrow frequency range (~100 MHz) and requires tuning the LC circuit to the correct frequency before measurements can be made and the design can become complicated if wider frequency range tuning is desired. An 50v bench power supply can be made using electronic diagram below which is designed using LM10 op amp and 2n3055 transistors. This LM10 2n3055 50v bench power supply allows an output voltage regulation in a range between 0 and 50 volts and the output current can be limited to a maximum of 2A. Output voltage increases linearly with the amount of resistance potentiometer P1, while the current can be adjusted linear using potentiometer P3. Potentiometer P2 serves to regulate maximum output current (maximum value is 2A).

Not thrilled with how a computer soundcard drove my 32ohm headphones so I decided to build myself class-A mosfet headphone amplifier. As with most of my projects, the goal was to keep it simple, keep cost down and try use some salvaged parts. This is a simple do-it-yourself (DIY) headphone amplifier project that is fashioned primarily after the Class A MOSFET Headphone Driver project by Greg Szekeres and to some extent Mark's DIY Class A 2SK1058 MOSFET Amplifier Project. The amplifier concept is simple and follows a typical single-ended class A circuit utilizing an active constant current source (CCS) in place of a passive resistor. A CCS doubles the efficiency of the circuit over that where a passive load resistor is used, bringing it to a maximum of 25%. This is a basic universal variable Power Supply voltage regulator circuit using an LM317, 3-terminal regulator in a TO-220package.

The Universal Power Supply output voltage can be set to anywhere in the range 1.5V to 30V by selecting two resistances. By using a potentiometer, R2, as one of the resistors you can dial up the output voltage wanted. Either AC or DC input can be supplied to the PCB via a socket or terminal block.

Connection can be either way around. This is because we have provided a bridge rectifier on board. The input DC voltage to the regulator must be at least 2.5V above the required output voltage. An off/on switch is provided.

For many applications (say 12V at 60mA) a heat sink will not be necessary. The LM317 will provide slightly higher output voltages than 30 volts. However, for most hobbyists over 30V will not be needed. So to make a small PCB we have used some electrolytic capacitors rated to 35 volts. To be safe for continuous operation the maximun input DC voltage to the regulator should not be over 33V. With a 2.5V to 3.0V drop across the regulator this will give a regulated output of 30V.

You can draw up to 1.5A from the LM317. If you need higher then use an LM338T rated to 5A. I'm not sure what motivated me to decide on building a high-gain tube preamp of this sort. Maybe it was the tube computer sound card idea I have seen, or the fact that I have enough junk to fill a dump truck.

What ever it was, it all started with a cute little plastic Hammond enclosure that had been on my shelf for a couple of years. I originally thought I might use it for a tube headphone amp, but in the end realized there would not be enough space for the three tubes needed to make a head amp. This is a high gain preamplifier that is suitable for use where a lot of gain is required - to drive a power amplifier that needs plenty of gain or perhaps for use with instruments, like a guitar or microphone. If you need less gain, take a look at the RCA 12AU7 / ECC82 Cathode Follower Tube Preamp Schematic which has a gain of about 8. This is simple to build audiophile class-A tube headphone amplifier.

It is based around 12AU7 / ECC82 audiophile vacuum tube that provides warm, rich and smooth sound expected from audiophile amplifiers. The 12AU7 (ECC82) is a Twin Triode vacuum tube, it is very popular in the audio world because it is rather rugged and can be operated at lower voltages. Headphone amplifier and 12AU7 tube is powered by just 12V DC voltage. This is great news for those new to vacuum tubes that want experience and learn more about them.

Typically vacuum tubes operate at high and dangerous voltages so you must have some experience and know what you are doing. On the other hand this headphone amplifier operates at low 12V voltage so it is safe to build and experiment. This Class-A Push-Pull Tube Power Amplifier uses a Pair of Push-Pull Class A, Ultra Linear Mono Block Tube Amplifiers that can be used with several different vacuum tubes including KT77 / 6L6GC / KT88 with a 12SL7 driver and 6NO30 tubes.

The amplifier stage is based on the Compact Hi-Fi Power Amplifier. One thing about DIY audio is that it is a journey, not a destination, it never ends. One project leads to another. The only limits are time and money. DIY audio is a lot about perfection. While I was quite happy with my previous tube amplifier projects, I felt there was room to improve (here comes the journey again). I like to be involved in the music.

If anything sticks out, it will degrade the experience. So I tend to like smooth response, lots of detail, wide soundstage and full spectrum of sound. These amps deliver all that in quantity. Regardless of what tubes I used for outputs, the sound is 'silky' and refined. A simple 200mW FM Transmitter circuit which covers frequencies from 88 to 108 MHz.

It is built with 3 transistors: BC109, BFR91A and BFR96S. It is quite stable and the output power is around 200mW. The first stage of transmitter is a mic amplifier but if you connect this radio transmitter directly to an audio source you can remove this stage and connect the audio signal to R5. U1, 1PH51C can be replaced with LM7805. You must use a stabilized power source for oscillator stage to prevent frequency variation. You can remove C7 and use a linear potentiometer instead of R6 with the median connector to C4, one pin to ground and the other one to +.

FM Transmitter uses MV2109 varicap diode and C7 for frequency tuning. A general purpose audio power amplifier is a must have for the electronics amateur.

It's not a good thing to use your HiFi set for an experiment, when there's a risk of blowing it's transistor out. Amplifier for your experiments should be simple in construction, durable, and easy to repair. Also a portable, low power consumption and battery powered.

Taking the considerations above, I gave you the PCB design for the TBA820M based amplifier. It is rated for 2Watts of RMS power output (16W PMPO) but gives even two times more if you cool it well by some tricks. I've been using this circuit for over ten years and personally still surprised by it's durability, thinking of how many short circuits and overdrives it is subjected. Presented here is zener diode meter for testing voltage value of an unknown zener diode. The zener diode or diode voltage regulator is a special diode, Unlike normal diodes these diodes are intended to work in the breakdown voltage and an essential part of the voltage regulator circuits. These components maintain constant voltage at its terminals suffer variations even when substantial current, its connection with reverse bias is normal also to work in the zener voltage of the source Vs must be greater than the rupture Vz, as always condition using a resistance Rs in series to limit current to a value always less than its maximum power.

The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in parallel the output impedance will be low so that it can directly drive an aerial of 1/4th wavelength. Since the output of N4-N6 is square wave there will be a lot of harmonics in it. The 9th harmonics of 10.7Mhz (96.3Mhz) will hence be at the center of the FM band.

N1 is working as an audio amplifier. The audio signals from the microphone are amplified and fed to the varicap diode.

The signal varies the capacitance of the varicap and hence varies the oscillator frequency which produce Frequency Modulation. With this circuit you can build a very small tracking transmitter that can be tracked using a FM broadcast band radio receiver. The transmitter can be powered from any 1.5V volt battery or power supply. Transmitter has a range up to 1 mile depending on battery voltage, height above ground, receiver sensitivity, and antenna length.

Under certain conditions distances of 1 mile have been achieved. It is recommended that this transmitter be used with FM radios that can tune continuously across the dial. The better the receiver and receiver antenna system the greater the practical range of the transmitter, however good functionality can be achieved with the least expensive radios and using only the standard telescoping antenna included with most radios.

Here's BH1417 USB FM Transmitter with built-in PLL circuit. Its low-frequency signal is converted into high-frequency, which can take any audio device with FM radio (stereo, car CD, MP3, DVD player, etc.), as a normal radio station. Transmitter power is sufficient for reliable reception of its signal within a few tens of meters. The basis of the device is a chip BH1417F, included in a typical scheme. This device contains all the necessary circuitry to generate a composite stereo signal c of the pilot tone, the RF generator with PLL and power amplifier. A detailed description is given in.

Here's a long range 300mW FM Transmitter for the 88MHz to 108MHz band. This particular TX is of special interest to those wishing to build low power Power Amplifiers for the VHF bands since it used impedance matching, power amplifier and antenna filtering, all of which should be used by radio constructors, whether it be for amateur radio or any other form of radio. The features of this project are: Higher output power - 150mW min (at 9v) and 300mW+ (at 12.5v). Very pure output signal due to careful design and filtering.

VARICAP modulation - possibility to add a synthesizer. Single sided Printed Circuit Board, only 40mm x 72mm. Covers the domestic FM band - 88MHz to 108MHz. Easy to build, but coil winding experience IS required. Here is a circuit for simulating breathing / pulsing LED with the 555 timer chip. It became very popular and i received many comments and emails with people that made this circuit and worked fine, as well as comments with people that had troubles converting it to operate at 12 volts supply. It was designed to operate with 5 volts, because i plan to use it for a future PC mod.

Since the PC power supply has 5 volts output, and since the LEDs that i plan to use require 3.8 volts to operate, choosing 5 volts for supply was the best choice to minimize power dissipation on the transistor. The objective of this 1.5V FM Broadcast Transmitter design is to provide a simple low-power transmitter solution for broadcasting audio from various audio sources. This transmitter accepts stereo input via two 470K resistors.

Since there is no audio level control on the input, the audio level out from the source needs to be adjusted. Or, you can just add a 10k as an input level control. Transmitter's frequency, as built is tunable via spreading or compressing the coil to the desired frequency, and the coil can be glued down. If you want to make one that's tunable, it might be easiest to reduce the 18 pf capacitor and put a small trimmer capacitor in parallel with the inductor (across the reduced value capacitor).

Voltage variable capacitors would be an nice alternative to a mechanical variable capacitor but they don't offer much tuning range with only a 1.5V power supply. This FM Broadcast Transmitter circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws about 30 mA from a 6-9 volt battery and can be received to about 100 yards.

A 555 timer is used to produce the tone (about 600 Hz) which frequency modulates a Hartley oscillator. A second JFET transistor buffer stage is used to isolate the oscillator from the antenna so that the antenna position and length has less effect on the frequency. Fine frequency adjustment can be made by adjusting the 200 ohm resistor in series with the battery. Oscillator frequency is set by a 5 turn tapped inductor and 13 pF capacitor. RF laboratory often requires capacitance meter for small capacitors in pF range. Such a device can easily be built by yourself.

Here, a measurement converter for PC serial port is presented. The frequency of an oscillator is reduced by the target and measured on a PC.

The appropriate conversion then allows the direct display of the capacity. The input uses a short and low capacitance probe tip. The opposite pole is clamped to ground cable with a crocodile. The NE555 precision timer receives its operating voltage directly from the serial interface and produces a measurement object without C is a square wave with a frequency of 3.5 kHz.

The signal is processed via the CTS input of the interface. For measurement purposes in the electronics laboratory is needed again and again signals of different frequency and waveforms. A common function generator provides sine, for example, triangular and square waves.

The frequency must be adjustable and at least cover the low frequency range. The low-cost IC XR2206 provides a very simple function generator with only a few external components. XR2206 data sheet provides complete basic circuit for a simple function generator. It requires an operating voltage of 12 V and delivers sine and square wave signals.

Instead of the sine wave output is obtained after opening of S1 a triangular output wave. XR2206 IC contains an internal VCO (Voltage Controlled Oscillator, Voltage Controlled Oscillator) with triangular and rectangular output. The capacitor C and the power to determine the frequency at pin 7. With a pot of 2 megohms and a fixed resistor of 1 kOhm variation gives a ratio of 1 to 2000 and may include a range of 10 Hz to 20 kHz sweep.

In this project, you will make a simple 3-stage low-power broadcast-type circuit, using a crystal oscillator integrated circuit and an a collector modulated AM oscillator with amplifier. You can connect the circuit to the an electred microphone or amplified dynamic microphone. Using an electred microphone is shown (in gray) in the diagram below.

(no amplified dynamic microphone has a to low output voltage to work. At least 100mv is needed).

You could also add a LF preamp stage of one transistor to allow connecting a dynamic microphone directly. You'll see that you can receive the signal through the air with almost any AM radio receiver. Although the circuits used in radio stations for AM receiving are far more complicated, this nevertheless gives a basic idea of the concept behind a principle transmitter. Plus it is a lot of fun when you actually have it working! Remember that transmitting on the 10 meter band you'll need a valid radioamateur license!! A wide range of different circuits have been used for AM, but one of the simplest circuits uses collector modulation applied via (for example) a transformer, while it is perfectly possible to create good designs using solid-state electronics as I applied here (T1 BC557). The transmitter is build as a Colpitts Oscillator with a BSX20 transistor.

HF-output of the oscillator is approx. 50 mW, depending on the supply voltage of 6 to 15 Volts. This is amplified by the BD135 and brings the power up to approx. 1 watt @ 12volts. The transmit frequency is stabilized with the 28Mhz crystal. A slight detuning of approx 1kc is possible when using a 120pF trimmer capacitor for C8. The oscillator signal is taken from the collector of T2 and guided to the input of T3 which output is lead via an L-filter and low-pass PII filter circuit cleaning up the signal pretty good and ensuring spectral purity.

The oscillator is keyed by T1 and the morse key (S). By keying the morse-key T1 is not been used for modulation and is biased, hence lets T2 freely oscillate. Here is 0 to 99 minutes relay timer using PIC16F628 microcontroller and 16 character LCD display. The microcontroller is PIC16F628A running at 4.0 MHz clock using an external crystal. An HD44780 based 16×2 character LCD is the main display unit of the project where you can watch and set the timer duration using tact switch inputs.

There are three tact switches connected to RB0 (Start/Stop), RB1 (Unit), and RB2 (Ten) pins. You can select the timer interval from 0-99 min using Unit and Ten minute switches. The Start/Stop switch is for toggling the timer ON and OFF. When the timer gets ON, a logic high signal appears on the RA3 pin, which can be used to switch on a Relay. The circuit diagram of this project is described below.

Presented schematic shows how to build simple PIR motion detector sensor. PIR sensors allow you to sense motion, almost always used to detect whether a human has moved in or out of the sensors range.

They are small, inexpensive, low-power, easy to use and don't wear out. For that reason they are commonly found in appliances and gadgets used in homes or businesses. They are often referred to as PIR, 'Passive Infrared', 'Pyroelectric', or 'IR motion' sensors. PIRs are basically made of a pyroelectric sensor (which you can see above as the round metal can with a rectangular crystal in the center), which can detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted.

The sensor in a motion detector is actually split in two halves. The reason for that is that we are looking to detect motion (change) not average IR levels. The two halves are wired up so that they cancel each other out. If one half sees more or less IR radiation than the other, the output will swing high or low. AM radio built around 555 timer chip. The only active device (silicon, germanium, or otherwise) is the LM555.

The tuning is accomplished with an inductor and a capacitor, and the LM555 acts as an AM demodulator and class-D power amplifier to drive the speaker. You may be wondering how all this is accomplished with a 555. Here’s how the circuit works: The AM radio signal is tuned by inductor L, which is 300 turns of wire on a 1/2 inch diameter cardboard tube made out of a paper roll, along with the 100pF variable capacitor.

One end of the parallel configuration of L and C connects to an antenna (surprisingly long!) and the other end connects to a ground wire which is tied to the AC outlet ground (old books tell you to ground it to a water pipe). So far this is exactly like an AM crystal radio. The 555 timer is configured as a pulse width modulator in a non-traditional configuration. If I used the standard approach and connected the input to the CV pin, the low impedance of the pin would prevent the circuit from receiving any radio signals.

I had to invert the circuit and tie both high impedance analog pins, Threshold and Trigger to the radio signal input. This is the reason why the CMOS version of the 555 timer performs much better than the standard bipolar, which has higher input bias current. This is a simple active antenna booster. This amplifier will pull in all distant FM stations clearly. The circuits is configured as a common-emitter tuned RF preamplifier wired around VHF/UHF transistor Q1.

Input coil L1 consists of four turns of 20SWG enameled copper wire (slightly space wound) over 5mm diameter former. It is tapped at the first turn from ground lead side. Coil L2 is similar to L1, but has only three turns. Pin configuration of transistor 2SC2570 is shown in the fm antenna booster schematic.

Adjust input/output trimmers (VC1/VC2) for maximum gain. Here's low power stereo amplifier built around TDA2822 chip. Many people may have heard of the TDA2822 before, but for those who haven't, it is a small power amplifier that will drive two channels. It is usually in an 8-pin DIL package, but older versions I have seen are 14-pin or similar (there are datasheets for both variants). For simplicity though, my circuits show schematics for the 8-pin DIL package. The datasheet is here, provided by ST. This article is based along the usage of the TDA2822M variant of the chip series as it is commonly available.

The TDA2822 is similar, but has slightly more pins so is less used. Here's 1W RF Amplifier is for boosting small fm transmitters and bugs. It use two Philips 2N4427 and its power is about 1Watt. At the output you can drive any linear with BGY133 or BLY87 and so on. Its power supply has to give 500mA current at 12 Volts.

More voltage can boost the distance but the transistors will be burned much earlier than usual.! In any case do not exceed the 15Volts. The Amp offers 15 dB in the area of 80Mhz to 110 Mhz. L4, L5, and L6 are 5mm diameter air coils, 8 turns, with wire 1mm wire diameter.An easy project, with great results. I built my first power amplifier when I was still in secondary school. The circuit was made of transistors, didn't provide much power and had an ugly PCB.

Around the same time I got access to a datasheet of TDA1524, a tone/volume control circuit, and I decided to use it to build a pre-amplifier, to improve the quality of the sound coming out of the amplifer. Both circuits worked well for almost a decade but the old amplifier was never up to my expectations. In 2006 I decided that it was time to build a real power amplifier, this time based on an integrated circuit to reduce the number of external components and cost. A high quality stereo FM transmitter circuit is shown here. The circuit is based on the IC BA1404 from ROHM Semiconductors.

BA1404 is a monolithic FM stereo modulator that has built in stereo modulator, FM modulator and RF amplifier. The FM modulator can be operated from 76 to 108MHz and power supply for the circuit can be anything between 1.25 to 3 volts. In the circuit R7, C16, C14 and R6, C15, C13 forms the pre-emphasis network for the right and left channels respectively. This is done for matching the frequency response of the FM transmitter with the FM receiver.

Inductor L1 and capacitor C5 is used to set the oscillator frequency. Network C9,C10, R4,R5 improves the channel separation. 38kHz crystal X1 is connected between pins 5 and 6 of the IC. Composite stereo signal is created by the stereo modulator circuit using the 38kHz quartz controlled frequency. This is an add-on over voltage protection circuit for LM317 voltage regulator.

It is a voltage regulator that allows a 6V portable supply to be derived from the 12V car battery. You can add a 6.2V zener diode and a LED to warn you when the input supply is overvoltage. If you could find a relay that would operate from 6.2V right up to 12v that you could connect in such a way that if over voltage occurred, then the relay would automatically switch off the output preventing damage to any connected equipment. Such a relay would be quite difficult to find, so I designed this, it is a simple two transistor circuit which will switch off the output should the voltage raise above 6.2v this can be changed by selecting a different value of zener diode. This is a simple design of a small FM Transmitter Bug that's perfect for transmitting and eavesdropping purposes. Due to the high sensitivity, even the ticking of the clock to hear. The range is estimated at anything from 50 meters.

With a small piece of wire as an antenna to get at least the whole house. L1 and L2 are two equal air pools. They each consist of 5 turns at a diameter of about 4 mm. The thickness of the wire does not matter, 0.5 mm works perfectly. C4 is the frequency adjustment. Tune an FM radio in an empty area of the FM band and C4 to turn your silence or hear a whistle.

From what you can precisely adjust the radio and the transmitter installed in a room somewhere to intercept. Note: Because these transmitter bugs inherently unstable, you better read the short legs of the components keep the circuit mechanically tightly together up. Also placing a 1 nF capacitor (C6) will benefit stability. R1, R3, R4: 4K7 R2: 100K R5: 10K R6: 270 Ohms C1, C2: 10 uF C3, C6: 1 nF C4: 2-18 pF trimmer C5: 5.6 pF L1, L2: air puddle windings on May 4 mm in diameter (see text) T1, T2: 547 BC Condenser microphone Original Text: Ook het plaatsen van een 1 nF condensatortje (C6) over de voedingsaanluitingen komt de werking ten goede. [Origineel TinyCAD ontwerp] Show alternative translations. Presented here is a circuit for 30V 10A variable bench power supply that offers variable voltage and current adjustment. Power supply is based around a LM723 voltage regulator chip and has current limiting.

I often end up with the power clips shorting out on the bench and with no problems. I have had this circuit in use now for over 20 years and has never let me down and is one of the most handiest gadgets i have built. The 2N3055 transistors are a well proven high current transistor. More 2N3055 transistors can be connected together for more output current. The transistors will need to be mounted on a good size heatsink. This miniature transmitter is easy to construct and it's transmissions can be picked up on any standard FM receiver. It has a range of up to 1/4 of a mile or more.

It is great for room monitoring, baby listening, nature research, etc. L1 is 8 to 10 turns of 22 gauge hookup wire close wound around a non-conductive 1/4 inch diameter form, such as a pencil. C4 is a small, screw-adjustable, trimmer capacitor. Set your FM receiver for a clear, blank space in the lower end of the band.

Then, with a non-conductive tool, adjust this capacitor for the clearest reception. A little experimenting and patience may be in order. Most of the parts' values are not critical, so you can try adjusting them to see what happens. Several years ago, National Semiconductor came up with some very high performance, easy to use audio power amplifier LM3886 circuits. I needed an extra amp so I can bi-amp some of my homemade electrostatic speakers so I tried the LM3886 chip.

LM3886 amplifier was chosen because of ease of use, performance, low distortion and a built-in protection against short circuits and thermal instability. There is not much to remove a power amp, than asking. When driving electrostatic speakers, you can not be much protection. There are people who have “golden ears” and the feeling, provided that no application note scheme is never good enough for it to “Optimize” to “improvements” to make a claim.

The problem is that most of them do not engineers and have no idea what the possible consequences of their “improvements” can be. For example, for a few years if these chips were popular with the audiophile crowd, it was all the rage at minimum power filter caps for “Best Sound” to use. We are talking about 500 uF on each power rail for each chip used LM3886 amplifier. This is clearly insufficient and leads to a distortion in the volume low enough that the power supply sags under load. The problem was that some of the golden ears of the large power supply rejection IC spec saw and thought it meant that the chip could tolerate the 10V power supply ripple. The pendulum has swung the other way, and now many music lovers are sufficient amounts of energy storage in the diet.

This TV transmitter transmits audio and video signal from Camcoder Camera, DVD, VHS, Satellite, video game, etc. Playing them in a channel free from the strip of VHF. These signal can be radiated with a common antenna and captured in an it distances of until about 500 meters that it is the most appropriate for urban areas, reminding that and necessary to be a lot of caution and careful for not interfering in frequencies of other issuing, as well as to emergency services.

Depending on the local conditions (existence or not of obstacles). Fed with tensions from 12 to 15 Volts, the circuit has excellent I carry out so much in the emission of monochrome signal, as in colors.

An important point of this project ‚the easiness with that he can be set up and adjusted, since only two coils are used. Ideal to be used with surveillance cameras turning the without thread. As it Works the tv video and audio transmitter with lm1889n The heart of this circuit transmitter ‚is the integrated circuit LM1889N of National Semiconductor, that consists of a Modulator of Video for TV in an involucres of 18 pins DIL.

Even if the digital multimeter have dominated in a lot of applications, in the measurement, exist the need for existence of instruments of clue in various appliances, voltage and current, as in power supply or elsewhere. The circuits that give make this precisely the work, measure the voltage in terminal a circuit and the current that passes in his. The circuit does not present particular difficulties for somebody that has a small experience.

The two circuits are the himself, with a small difference only in their input, when they have they measure voltage or current and in connection that concern decimal point [ dp ]. In the department of input IC1 and IC3, exist the CA3161E, that is a A/D Converter for 3-Digit Display. In the drive of Display IC2 and IC4, exist CA3161E, that is a BCD the Seven Segment Decoder/ Driver.

As it appear in Fig.1, that concern the voltmeter in input [ + IN ], exist in series a what resistor R1 in combination with the R3 create a voltage divider. On the contrary in the Fig.2 that it concern the ampere meter, this resistor does not exist, because the circuit is connected differently, thus the current pass through the R5, creating a fall of voltage, in her terminal, proportional current that it pass from this. Here is the circuit diagram of the simple FM transmitter using a transistor. Great performance or range is not guaranteed here, because this is an elementary design. General purpose radio frequency transistor BF 494 (Q1) is used here for obtaining FM modulation. A condenser mic is used here to pickup the sound.The condenser mic converts the sound to electrical variations and this variations are fed to the base of Q1, which performs the amplification as well as modulation.The capacitor C2 and L1 determines the frequency of transmission.The circuit can be powered from a 9V transistor radio battery.

FM transmitter or often called fm transmitter uses 2 transistors in this article uses 2 transistors 2n2222. If the fm transmitter is in use voltage supply of 9 volt battery and use an antenna whose length is less than 12 inches, then this fm transmitter will be within FCC limits. Signals from the microphone in the fm transmitter is reinforced by Q1, Q2 with carrier frequency generator is determined by the C5 and L1. The frequency of the FM transmitter is in the range 80 MHz - 108 MHz. L1 can be made ​​with as many as 24 e-mail wire wrap and 6 wrap.

The following is a picture series for the fm transmitter fm transmitter referred to in article 2 of this transistor. FM Radio Receiver IC TDA 7012T is very simple, but Radio This FM receiver has good sensitivity and selectivity. Single Chip TDA 7012T FM Receiver is to build an FM receiver requires a few additional components.

Feature contained in FM receiver IC TDA 7012T is quite tempting to an FM receiver. Among features an FM receiver TDA 7012T is a low-voltage applications micro affability arrangement (MTS), Frequency Locked Loop (PLL) to 76 KHz range and selectivity of FM receiver with RC Filter. In an article by FM Radio Receiver IC TDA 7012T can be seen in the FM receiver circuit which can be made​​. If you want to be independent of the local radio stations for testing VHF receivers, you need a frequency-modulated oscillator that covers the range of 89.5 to 108 MHz — but building such an oscillator using discrete components is not that easy. Maxim now has available a series of five integrated oscillator building blocks in the MAX260x series which cover the frequency range between 45 and 650 MHz.

The only other thing you need is a suitable external coil, dimensioned for the midrange frequency. This equipment is dedicated for an easier control of the popular mini-transceiver AT Sprint known by ham radio operators as ATS (series ATS-2, ATS-3, A, B, B.1 compatible). Originally the ATS has just four push buttons on the top cover and in combination with the paddle it is possible to send all commands to ATS including the tuning, scanning etc.

After connecting the rotary encoder accessory module an easy tune, scan and other functions are available as same as on the big size desktop transceivers. Comfort and operation is much higher even with this mini transceiver. I wanted to share my project of modifying the temperature sensor project and turning it into a thermostat with ATmega168.

I added a digital output to drive an LED to 'warm' the temperature sensor when the current (actual) temperature falls below the desired temperature. Two push buttons come in as digital inputs one to ramp the desired temperature up and the other to ramp it down.

The logic is simple bang-bang control to turn the LED on and off based on the relationship of actual temperature to desired temperature. It simulates a thermostat in heater mode. The LED is off when the current temperature is above the desired temperature and turns on once the current temperature falls below. USB AVR Programmer for Atmel AVR microcontrollers. USB AVR Programmer is made of an Atmega8 and few components.

The programmer uses a firmware driver that makes this programmer attractive to many amateurs. Another thin why this programmer is so popular is because it is officially included and supported in WinAVR.

Once again lets see what this programmer is made off and how to set it up. The core of USB AVR Programmer adapter is Atmega8 microcontroller clocked by 12MHz crystal. Soldered board is ready to be connected via simple USB cable with B type connector (Computer side needs A type of connector). Resistors R2 and R6 are current limiting resistors, that protect computer USB port. Resistor R7 helps computer to recognize device as LS (Low Speed). Diodes D1 and D2 indicates about data transfer.

Header SV1 is compatible with STK200/300 just 4 and 6 pins are used for RXD and TXD (may be used for other purposes). I’ve built myself my own universal, adjustable bench power supply. This isn’t strictly astro stuff but the main reason I built it is to experiment with TFT backlight panels that I use for my lightboxes. I needed 5V and 12V to play around with the inverter boards and figure out their pin-out.

I considered buying a bench power supply. But prices were too high, especially for ones with adjustable voltages. So I decided to build my own. This one has 4 outputs.

One 5Volt, one 12V and two individually adjustable outputs going from about 1.5V to 19.5V. Each can draw up to 1.5Amp with a total of 3.5A for all together.

The input is a standard replacement laptop power supply 20V, 3.5A. With a stronger external power supply the total output current can be higher, up to 1.5A per output. But currently the 3.5A is more than enough. Each of the adjustable outputs has its own little voltmeter built in.

The fixed voltage regulators are based on a 7805 for the 5V and a 7812 for 12V. The two adjustable regulators are based on one LM317 each. This RF Amplifier designed for FM broadcast using a single 2SC1946 VHF Power Transistor. This 10-30W RF amplifier circuit provides an appropriate power boost with an input of 1-3 watt. Tower are 30 meters high will send signal surrounding air should be around 15 km. The layout of the 2SC1946 28 Watts FM broadcast RF amplifier has been created with Eagle.

The pcb outline is 100 x 50 mm (width x height), all bitmaps have a resolution of 600dpi.Use FR-4 single sided photoresist epoxy pcb material for best results. This project uses a Microchip PIC microcontroller, a serial EEPROM and a thermistor to create a temperature recorder. The temperature is measured and stored at user programmable intervals; this can be from 1 second to 256 seconds. The time interval is set by programming it and the start time into the EEPROM.

Most of the time the PIC will be asleep and the EEPROM IC is inactive. This gives a very low current consumption of approximately 50 uA or about 1 mAh per day. The EEPROM used is 32kBytes which can store up to 32,000 measurements. This could be one measurement every 30 seconds for 11 days for example. The combination of thermistor and analogue circuit gives a range of between about -40 °C and +100 °C although the linear range is between about -10 °C and +40 °C.

Automatic battery charger automatically starts the charging procedure when battery voltage drops below a certain predefined value and stops after the voltage has risen above the maximum allowed value. Setup can't be easier, just connect two alligator clips to battery terminals and plug the device in mains. This way it can stay connected for months and the battery will never overcharge. This comes very very handy when you have a scooter or a real motorcycle that you don't drive during the winter time. Because we all know what happens to a battery when not used and especially during the winter. There are many types of power supply. Most are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronics circuits and other devices.

A power supply can by broken down into a series of blocks, each of which performs a particular function. Each of the blocks is described in more detail below: Transformer - steps down high voltage AC mains to low voltage AC. Rectifier - converts AC to DC, but the DC output is varying. Smoothing - smooths the DC from varying greatly to a small ripple. Regulator - eliminates ripple by setting DC output to a fixed voltage.

Here is a very simple circuit that can b e used to check the hfe of transistors. Both PNP and NPN transistors can be checked using this circuit.

Hfe as high as 1000 can be measured by using this circuit.The circuit is based on two constant current sources build around transistors Q1 and Q2.The Q1 is a PNP transistor and the constant current flows in the emitter lead. The value of constant current can be given by the equation; (V D1 -0.6)/ (R2+R4).The POT R4 can be adjusted to get a constant current of 10uA. This is a simple water alarm. At the heart of this circuit is a small water sensor. For fabricating this water sensor, you need two foils—an aluminium foil and a plastic foil.

You can assemble the sensor by rolling aluminium and plastic foils in the shape of a concentric cylinder. Connect one end of the insulated flexible wire on the aluminium foil and the other end to resistor R2. Now mount this sensor inside the water tap such that water can flow through it uninterrupted. To complete the circuit, connect another wire from the junction of pins 2 and 6 of IC1 to the water pipeline or the water tap itself. This Wireless Microphone FM Transmitter has been a very popular project with beginners and experienced constructors alike.

It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and better microphone sensitivity. Now I can introduce the new FM Wireless Microphone, which also has a better frequency stability, over 1Km range (under ideal conditions) and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little. Build a simple data recorder for solar energy lab.

The Recorder uses a calculator solar cell as the input sensor and a Multimedia Memory Card for nonvolatile data storage. The device used for measuring daily insolation has been developed. The device was built with a PIC18F458 and the 128MB Multimedia Memory Card, MMC. The solar radiation is measured by a calculator solar cell.

The PIC chip interfaces the MMC using SPI mode. The interval between samples is set to one minute.

The firmware detects the memory card, assigns the file name and begins recording automatically. The LCD displays the file name, current sample and real-time ADC data. With the MMC flash technology and a cheap media card reader, the devices will be able to record huge amount of data and quick data uploading to the PC. Build a digital clock that turns AC load on/off through relay with preset time. The clock is based around 7-segment LED display with multiplex connection and AT89C2051 microcontroller.

It is nice to be used as the display for clock controller. So I spent my weekend built the board. Below are the pictures for outlook and internal. The board is quite small.

The output has small relay for 0.5A AC load. The program clock.c was written in ‘C’ language and was complied by Micro-C Compiler from DunfiledDevelopment Systems. The memory model is TINY.

The hex file of clock.c suitable for downloading by Easy-Downloaderis clock.hex. I needed a way to extract audio from a phone line for my DTMF decoder. I found a site full of examples on how to do it, and I built an interface that suited my needs: RCA output, with a signal strong enough to be fed directly to an audio amplifier or line-in. The interface can stay connected on the line at anytime (no problems with the ring signal), and does not take of the hook. The interface must provide isolation from the line. I discovered that it can also be used to inject audio in the line. The transmitters on my homepage seem to be quite popular, especially those intended for the 88 - 108MHz FM band.

I must really confess that I also favor this broadcast band, mainly because it is so easy to find signals on the workshop radio. Everyone has an FM radio, and it is fun to play with. Experimental antennas and the like can all be developed in this band since there are a huge range of 'beacons' all transmitting just for my benefit:-). Basic oscillators also are easy to fault-find in this frequency band, and then later modified for other VHF bands. The V5 FM Wireless Microphone is a 10mW transmitter that featured a coil fabricated on the PCB itself. This made the project easy to duplicate and removed 'microphony' (the ability of coils to act as a microphone with spring-line reverb).

But as several people have already commented, although more stable than most other similar kits and projects, the frequency still does vary with battery voltage. In just one session it can vary by 200kHz when a cheap 'Mighty Atom' battery falls to 8 volts. Here is a simple TV transmitter. The circuit is simple and really quite crude, but it does include MONO sound. I have not shown the two regulators in the drawing.

These are one 12v DC 1A series regulator chip, and one 8v DC 1A series regulator. I fed the 8v regulator from the output of the 12v regulator. The rest of the circuit looks like this. It is a free-running Variable Frequency Oscillator (VFO) using just one coil and one capacitor to determine the frequency. Change this as you will.

The basic circuit uses a 150pf from the Base of the RF transistor to ground, so that TR2 operates as a 'common-base mode' (grounded base) amplifier. The tuned circuit in the collector and the capacitor from collector to emitter provide tuning and feedback.

Here's AVR programmer for programming AVR microcontrollers such as the AT90S1200 via the parallel port. AVR programmer is extremely simple.

IC1 provides buffering for the signals that travel from the parallel port to the microcontroller and vice versa. This is essentially everything that can be said about the circuit. The two box headers (K2 and K3) have the ‘standard’ ISP (in system programming) pinout for the AVR controllers. The manufacturer recommends these two pinouts in an attempt to create a kind of standard for the in-circuit programming of AVR microcontrollers. These connections can be found on many development boards for these controllers. The software of AVR programmer carries out the actual programming task.

This RF inductance meter measures RF chokes in the 500 nH to 50 uH range. I needed a way to measure hand-wound RF inductors in my second lab, and since I would only be doing this occasionally, I didn't need anything fancy, and since once a friend finishes his AT90S1200-based design, I plan to make one myself, I figured I'd use this for less than a year, so I didn't want to invest a lot of time in making it. I had run across the forerunner of this circuit, one that is more sophisticated in that it has a zero adjustment and range switch, but it was limited to higher inductances. I adapted it to the components I had on hand and changed it so that it would work in the 500 nanohenry to 50 microhenry range.The original circuit was reportedly published a few years ago by the Amrican Radio Relay League, so it is with appreciation of the ARRL that I make this circuit available. Here's a simple to build hybrid tube headphone amplifier built around 12AU7 / ECC82 vacuum tube. I have always been intrigued by tube amplifiers, but most DIY kits are very expensive and use very high voltage. So I decided to build an amplifier that would be inexpensive and had the least amount of parts necessary to drive a pair of 32 ohm Grado headphones.

Having built several YAHA amps based on the fa-schmidt design, and a Szekeres Mosfet follower I wondered how the two would sound together. So I built the schematic into TINA-TI, a free spice based program to test circuits before the build, and the results were remarkable. Nearly 20dB of gain across 20Hz-100kHz from a 13VDC power supply. As you see in the schematic and parts list, there are less than 30 discrete components and most DIY'ers will have them as spares from other builds. I chose the 12AU7 / ECC82 vacuum tube because it can be driven with low voltage and the filament voltage is 12.6 volts, so there is no need to regulate the voltage any further. I used 1/4W resistors in the first stage and 2W in the second.

The 2W resistors may be overkill but I did not want to change them later. The 20ohm resistor must be a minimum of 5W and do not use wire wound, as the inductive characteristics will distort the response curve. This is inductance meter I built using 74HC14 IC. Initially I used a DMM as the display device, but on a whim I tried hooking up a moving-coil meter. To my surprise, it actually worked just fine, 1K in series was sufficient to allow a useful calibration and didn't overload the drive capabilities of the last gate in the package. I calibrated my unit for 0-100 uH, as this is the range I am generally most interested in, and it gives direct-readings on the uA scale of the meter. With the values as Dick specified, there is sufficient range to calibrate it from about 25 uH to 250 uH FSD.

This is USB sound card with PCM2902 chip. For the purpose of testing the D / A converters, I built a simple USB sound card with the circuit PCM2902. The card has analog input and output, an electrical S / PDIF output, galvanically separated input and optical input and output TOSLINK. The heart of USB sound card is PCM2902 it is a circuit connection, which is a complete USB codec. The circuit can handle up to 48kHz sampling frequency.

The integrated circuit includes a USB controller for A / D and D / A converter, HID part for 3 buttons, volume control, custom converters and S / PDIF encoder and decoder. Presented here is a 1.5 Watt FM Transmitter. Lipoly batteries are great power source for our AEGs, they offer high current capacities and are available in different shapes and sizes that can fit virtually any AEG. But they have a downside, they are prone to failures when over discharged.

Their nominal voltage is 3.7V (4.2V-full charge) but must not go below their critical voltage of 2.7V. New development in AEG electronics protect the battery from going too low by either cutting the power or an audible warning that indicates low battery voltage. While saving up for the 'Panther' or 'Cheetah' SW-COMP, here is a cheap and easy to construct 11.1V lipoly lo-batt indicator.

This is 100W LM3886 power amplifier. Since my DIY speaker is 4-ohm and somewhat difficult to drive, I want to have a more powerful amplifier to match with it.

Therefore I designed this amplifier which uses two LM3886 per channel, in parallel circuit. This amp can deliver about 50W into a 8-ohm speaker and 100W into a 4-ohm speaker. This is a stereo amplifier and therefore 4 LM3886s are used. The LM3886 circuit is in a non-inverted configuration, so the input impedance is determined by the input resistor R1, i.e. The 680 ohm and 470pF resistor capacitor filter network is used to filter out the high frequency noise at the RCA input. The 220pF C4 and C8 capacitors are used to shot out the high frequency noise at the LM3886 input pins. I used high quality audio grade capacitors at several locations: 1uF Auricap at the input for DC blocking, 100uF Blackgate for C2 and C6, and 1000uF Blackgate at the supply filter.

Most transmitter has several variable capacitors which are used to match impedance for transistors and antennas. I know people hate trimmers and so did I.

The reason is that it is difficult to trim a system if you can't measure the performances. To trim a transmitter you need to measure the output power. Most transmitter are tuned with a dummy load of 50 ohm to substitute an antenna of 50 ohm. Not everyone has a power meter, and how can you know that the antenna you connect is purely 50 ohm. If not, the hole trimming is waste of time!

What you would like to do is to measure the radiated power out from the antenna you actually are going to use. If you can measure the radiated energy field you can easy tune the system for max output field strength (max power). So, how can we measure the radiated energy field? The block diagram at right show you one easy way to measure the RF filed strength. To the left you find a dipole antenna.

The antenna should be cut to match the receiving frequency. This is 80W RF power amplifier that boosts FM Transmitter's power using 2SC2782 bipolar transistors in a tuned class C circuit. RF amplifier can be driven to full 80W power with less than 1 watt driving input power, so that a large gain margin results in this FM transmitter. To obtain stability in this RF amplifier, I employed several techniques, such as placing the resonances of base and collector chokes far apart, damping the chokes with resistors, using RC combinations for absorption of unwanted frequencies, using feed trough capacitors for bypassing on the board, etc.

It took some tweaking, but the amplifier ended up unconditionally stable. This is a TV transmitter for transmitting video of various video sources such as video cameras, Satellite receivers, DVD players, game consoles, etc. TV transmitter's circuit is working on the 470-580 MHz frequency and can be received on UHF channels 21-34.

TV Video transmitter can radiate as far as 300 meters by using a 10-20 cm wire antenna. TV transmitter requires voltage of 9-15 Volts. However, you can also use a 9v batteries. Oscillator is based around BF199 and BFR90 RF transistors. If needed the range of TV transmitter can be extended by replacing BFR90 with 2N3886 transistors. A bootloader enables download of hex-files directly into the flash-memory of a PIC or other microcontroller.

The bootloader receives the user program via the PIC's UART and writes it directly to the program memory (self programming). This feature greatly speeds up the development process, because the chip remains in the target circuit and need not be moved between the target circuit and the programmer. When no bootloader is installed, all memory in the PIC can be utilized for user programs.

That is 4 K for the 16F873 (0x000 to 0xFFF). Installing a bootloader means, that some part of the memory is occupied by the bootloader. The user can download his program into the remaining memory space. The bootloader in figure 1 occupy 256 words (0xF00 to 0xFFF), that is 6% of the memory in a 16F873. The disadvantage of loosing 6% memory is little compared to the advantage of fast program download and more friendly development routines.

This is LiPo battery charger circuit based around the MAX1551 / MAX1555 chip from Maxim ICs. And it happens to be a very easy chip to use.

I used the typical circuit from the datasheet and referred to the pin out to see which pin is what. I also used adapter board so that I could prototype the LiPo battery charger on a breadboard. The barrel plug towards the top goes into an LM7805 that can take 7-16V and regulates it down to 5V. Besides that, pretty simply stuff with only a handful of common components. Here's how to build a simple FM Transmitter.

This tiny transmitter has smaller radius of the service area, lower quality of the sounds and the relatively unstable frequency. These can be considered as a compromise to easily have your own transmitter for the time being or as a more positive choice.

These 'defects' are only from the perspective of conventional transmission such as 'clear stereo sound to receive anywhere'. Artist could change these to another directions. Whether or not, you can experience a convivial wireless imagination by this transmitter. This micro spy PLL FM Transmitter transmits on the 160MHz frequency (if we use a 40MHz quartz) and therefore can be listened through a receiver tuned on this frequency. This circuit can be used to on various frequencies, for example on the FM band 88-108 just modifying some components, among which the quartz (25MHz).

Voice is detected by an electret microphone, then it is amplified and filtered by U1 pass-band in order then to be modulated from the carrier section, where through the varicap diode it 'mixes' with the frequency generated by the quartz, that guarantees an adapted stability. Practically the modulating voltage is obtained applying the audio signal to the resonating circuit varicap diode that determines the carrier oscillation. The carrier frequency (160 MHz) must be greater than the modulating frequency (300-3300 Hz) audio band.

The transmission is on the fourth harmonic, therefore 160MHz, the oscillation frequency of the driver RF transistor Q1. A small calibration is allowed acting on the L1 inductance and the C1 Trimmer Capacitor.

We love to read emails from our visitors, Please let us know by clicking here if you find any kind of bug/error in our site. We will fix it as soon as possible. PIC Controlled Relay Driver This circuit is a relay driver that is based on a PIC16F84A microcontroller. The board includes four relays so this lets us to control four distinct electrical devices. The controlled device may be a heater, a lamp, a computer or a motor. To use this board in the industrial area, the supply part is designed more attentively. To minimize the effects of the ac line noises, a 1:1 line filter transformer is used.

Mini FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps. When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance. I've seen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc. Here is the last step of this evolution, the most stable, smallest, problem-less, and energy saving champion of this race. Circuit given below will serve as a durable and versatile FM transmitter till you break or crush it's PCB.

Frequency is determined by a parallel L-C resonance circuit and shifts very slow as battery drains out. This is a scaled-down version of Nelson Pass' Zen power amplifier for my headphones. For this use, the Zen topology is perfect excellent sound quality, simplicity, linearity and no multi-stage feedback. It is a single stage class A MOSFET design with the right gain and a low output impedance. Here we don't have the limitations of the Zen amps at least in the single-stage implementations regarding speaker compatibility.

A single stage topology with correct interfacing values misses very few things in the original music message. The gain device in the original Zen amplifier is biased by fixed current source. For this amp, I employed an active current source described in Pass' patent no. 5,710,522 (see Zen Variations Part 2). The benefits of an active source include higher output current, lower distortion and 50% theoretical operating efficiency (compared to the 25% efficiency from a fixed source). This type of current source is featured in the Aleph power amplifiers from Pass Labs. In today’s hectic and noisy world, we are all searching for a little peace and quiet.

Well, you might not be able to slip off to a tranquil forest for an hour or two, but you can block out background noise with the Noise-Canceling Headphones. The theory behind this project is that by picking up ambient sound with a microphone and reproducing it out of phase, we can actively cancel or 'null' out background noise. In fact, several commercially available devices perform the same function. However, by building your own headset, you can add features not otherwise available and have fun while doing it! Along with noise-features, the Active Noise-Canceling Headphones let you mix in an auxiliary line-level signal from a CD or tape player. That allows you to minimize background noise while quietly listening to music. The project also has a phase switch that will let you keep the microphone signals in phase, thus amplifying background sound.

In addition, the design of the Noise-Canceling Headphones lends itself to several other interesting functions, which we will look at later. This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you. Ear amplifier is powered by 1.5V battery and draws only 7.5mA of current.

The heart of the circuit is a constant-volume control amplifier. All the signals picked-up by the microphone are amplified at a constant level of about 1 Volt peak to peak. In this manner very low amplitude audio signals are highly amplified and high amplitude ones are limited.

This operation is accomplished by Q3, modifying the bias of Q1 (hence its AC gain) by means of R2. This is simple to build AVR programmer for Atmel microcontrollers from AVR family. The microcontrollers must support serial programming.

AVR programmer is connected to a PC through the RS232 serial interface and can be used with the PonyProg or Avrdude software programmer. AVR programmer is quite simple and it is based on the SI-Prog from the author of PonyProg software. AVR programmer can be used for programming Attiny13, Attiny26, Attiny2313, Atmega48, Atmega88, Atmega168, Atmega16, Atmega8 and it works very well. I also use the programmer with desktop computer, laptop, with and wihout USB-to-RS232 adapter and it works in all cases. Several years ago, National Semiconductor came out with some very high performance, easy to use audio power LM3886 amplifier ICs. I was in need of an extra amplifier so I could biamp some of my home-built electrostatic loudspeakers so I tried the LM3886 chip.

LM3886 amplifier was chosen because of the ease of use, power output, turn-on and off thump suppression, low distortion, and built-in protection against shorts and thermal runaway. There isn't much more to ask of a power amp than that. When driving electrostatic speakers, you can't have too much protection.

This Field Strength Meter has been specially designed for our FM bugs. It is capable of detecting very low power transmitters and will assist enormously in peaking many of our FM transmitters that have a coil in the output stage that can be adjusted for optimum output. Up to now, field strength meters have only been able to detect transmitters with an output of 100 milliwatts or higher, and for an output such as this, a simple circuit such as a meter and a coil is sufficient. But when it comes to a low power device, a simple circuit, with no amplification, is not suitable. We spent more than 5 days building all the circuits we could find - that purported to be suitable for low-power transmitters, hoping to find one that would work. Unfortunately none came anywhere near good enough so we had to design our own. The circuit we came up with is shown above and it incorporates an RF amplifier, diode rectification, and a DC amplifier so that a movement from a multimeter (a movement is the 'meter' part of a multimeter) could be used as the readout.

The heart of the design is a pair of diodes that are partially turned on via a resistor (the 100k sensitivity control) and this overcomes some of the.6v threshold of a diode. You may not think.6v is very much but when you are talking in millivolt terms, it is 600 millivolts. The signal we are attempting to pick up produces one or two millivolts on the receiving antenna and if you need 600 millivolts to turn a diode ON, the field strength meter becomes very insensitive. Here's 75 Meter QRP SSB Transceiver. In general, the transceiver switches the 4-element 1500 ohm xtal BPF ends between the inputs and outputs of the two SA602s to reverse the signal flow for R/T operation.

Since no IF amplifier is used in the design, 20 dB of additional receiver gain is produced by the 2N2222 receiver RF amplifier, while automatic gain control (AGC) is produced by the peak DC swing of the LM386 output passed through a rectifier and filtered by a capacitor and fed to the gate of a BS170 enhancement mode FET acting as a variable resistor across the input of the LM386. Both receive and transmit band pass filtering are done by the same half-pi BPF. The diode pair in the mic circuit reduce the 'chirp' that occurs during the R/T transition. Additional BS170s could easily be used to mute both the mic and audio instead of the R/T switch directly. These BS170s would be controlled by the +R and +T voltages on their gates while their drains would be tied to 1) the mic circuit between the two coupling capacitors and 2) pin number 1 (audio in) of the LM386 (BS170 sources to ground). Additional power output (perhaps 60 mW) could also be attained by connecting the RF output transistor's collector choke (10 uH) to a 9 V supply instead of the 5 V.

Additional biasing current might also be required for this change. Gainclone amplifiers have very few components and this one is based on the National Semiconductor LM3875 IC. The PCBs and components are very simple and quick to make, only took about 20 mins to assemble both amps and rectifier board. DC offset was about 80mV on one channel and about 40mV on the other. I used the optional Ci capacitor in the national datasheet for the IC which reduced it to between 0-4mV: This is the capacitor I chose, its an Elna Starget (expensive). The case was MUCH more time consuming and difficult to make though.

I bought all the aluminium from a scrap metal yard including the heatsink. I got my aluminium panels cut at a sheet metal shop as I cant make straight cuts with a hack saw. This is high current 12V power supply. Power supply uses LM7812 IC and can deliver up to 30A to the load by the help of the TIP2955 pass transistors. Each transistor can handle up to 5A and six of them result an total output current of 30A. You can increase or reduce the number of TIP2955s to get higher or lower current outputs.

In this design the IC delivers about 800mA. A 1 amp fuse is connected after the LM7812 to protect the IC against high current transients. The transistors and the 12V regulator IC both require adequate heatsinking. When the load current is high, the power dissipation of each transistor also increases so excess heat may cause the transistors to fail.

Then you will need a very large heatsink or fan cooling. 100Ω resistors are used for stability and prevent current swamping as the tolerances of dc current gain will be different for each transistor. The bridge rectifier diodes must be capable of passing at least 100 amps.

Arduino Sine wave Generator using the direct digital synthesis Method. Here we describe how to generate sine waves with an Arduino board in a very accurate way. Almost no additional hardware is required. The frequency range reaches form zero to 16 KHz with a resolution of a millionth part of one Hertz! Distortions can be kept less than one percent on frequencies up to 3 KHz. This technique is not only useful for music and sound generation another range of application is test equipment or measurement instrumentation.

Also in telecommunication the DDS Method is useful for instance in frequency of phase modulation (FSK PSK). The DDS Method (digital direct synthesis). To implement the DDS Method in software we need four components. An accumulator and a tuning word which are in our case just two long integer variables, a sinewave table as a list of numerical values of one sine period stored as constants, a digital analog converter which is provided by the PWM (analogWrite) unit, and a reference clock derived by a internal hardware timer in the atmega. To the accumulator, the tuning word is added, the most significant byte of the accu is taken as address of the sinetable where the value is fetched and outputted as analog value bye the PWM unit.

The whole process is cycle timed by an interrupt process which acts as the reference clock. Further details of the DDS Method are described in web of course. This example shows how to make use of the Watchdog and Sleep functions provided by the ATMEGA168 chip (decimila). These functions are useful if you want to build low power consuming devices operated by battery or solar power. The reduced power consumption is achieved by through a intermittent operation of the system.In case of Arduino your main loop will be executed once before the system is put into the sleep mode. After a few seconds t the watchdog wakes the system up and the main loop is executed again.

The ratio between main loop execution time and watchdog time determines the amount of power that will be saved. When we assume that the time to measure a sensor and making some decisions will take 10 millisecond and the watchdog is set to 8 seconds the on/off ratio is 800 which extends the battery live time by this factor. This device is designed to measure the torque in an automobile drive shaft and provide an output to a vehicle data recording system or a portable computer via an RS-232 interface. The received data can then be combined with RPM measurements from the data recording system to calculate horsepower.

It consists of the sensor unit, (Figure 1), which attaches to the driveshaft, and the receiver unit,, which provides the serial output signal. The sensor unit is battery powered and communicates with the receiver via a 433 Mhz RF data link.The receiver unit is powered by the vehicle electrical system. Circuit operation is shown in the diagram. The linear laboratory power supply, shown in the schematic, provides 0-30 volts, at 1 amp current, using a discrete transistor regulator with op-amp feedback to control the output voltage. The supply was constructed in 1975 and has a constant current mode that can be used to recharge batteries. With reference to the schematic, lamp, LP2, is a power-on indicator.

The other lamp (lower) lights when the unit reaches its preset current limit. R5, C2, and Q10 (TO-3 case) operate as a capacitor multiplier. The 36 volt zener across C2 limits the maximum supply voltage to the op-amps supply pins. D5, C4, C5, R15, and R16 provide a small amount of negative supply for the op-amps so that the op-amps can operate down to zero volts at the output pins (pins 6). A more modern design might eliminate these 4 components and use a CMOS rail-to-rail op-amp.

Current limit is set by R3, D1, R4, R6, Q12, R10, and R13 providing a bias to U2 that partially turns off transistors Q9 and Q11 when the current limit is reached. R4 is a front panel potentiometer that sets the current limit, R22 is a front panel potentiometer that sets the output voltage (0-30 volts), and R11 is an internal trim-pot for calibration.

The meter is a 1 milliamp meter with an internal resistance of 40 ohms. Switch S1 determines whether the meter reads 0-30 volts, or 0-1 amp.

The USB-Servo is a device to control a servo via USB. A servo is a motorized device that is commonly used in remote controlled cars and planes. I built this device to activate a toy puppet. The puppet has a button on its bottom, if you press the button the puppet collapses. When the computer is able to press the button, I can use the puppet to signal information like someone's online-state in the Jabber-network: when my friend goes online, the puppet stands up, when he logs off it collapses.

Servos are connected with three-wire-cables. A red and a black one for the power, and a yellow one for the signal. Power has to be between 4.8 and 6 volts, so the 5 volts from the USB-port is in the range. The signal doesn't take much current, so you can connect it directly to the controller. The angle of the servo is controlled with pulse width modulation (PWM).

It gets a signal of about 50Hz (one pulse every 20ms), the length of the pulse tells the servo the angle to adjust. Here is a very simple project of controlling a small DC-motor (taken from an old personal cassette player) with ATmega8.

The ATmega8 is having three PWM channels, out of which two are used here. PWM waveforms are fed to MOSFET (RFD3055) H-bridge. Here, direction is controlled using a two-position toggle switch and speed of the motor is controlled by two push-buttons, one for increasing the speed and other for reducing. The schematic is geiven here (click on the image to enlarge): When switch SW1 is closed, OC1A channel is active which will feed the PWM signal to Q1 & Q4 MOSFETs.

The OC1B pin will remain low keeping the Q3 & Q2 in OFF condition. When SW1 is toggled to open position, OC1A pin will become low, making Q1 & Q4 OFF and OC1B will feed the PWM signal to Q3 & Q2, resulting in the change in the direction of current flow through motor. Hence, motor rotation direction will change. The speed is controlled by Push-buttons S2 & S3. Pressing S2 will increase the speed in fixed steps. Similarly, pressing S3 will reduce the speed in fixed steps. Presented here is high quality USB DAC PCM2906 with built-in headphone amplifier.

To see one or more of the same sound card than this is a compact device. That acts as the computer sound card is easy to use.

Just plug into a USB port on your computer. It can be used immediately within an IC in PCM 2906 Burr Brown's brand of Neu hear all agree that the sound of course. Used to convert digital signals from the USB port can adjust volume and mute the signal with Noise from the hard drive or CD player can not come to interference. Because a separate circuit from the computer.

Add power to drive headphones with a Single Supply OPA2353 Opamp serves as Headphone Amp that does not reconcile the external power supply. This may be an alternative for those who are looking for sound card priced tight, but the quality of glass. This DIY lightning detector circuit is a very sensitive static electricity detector that can provide an early warning of approaching storms from inter-cloud discharge well before an earth-to-sky return strike takes place. An aerial (antenna) formed of a short length of wire detects storms within a two mile radius.

The circuit emits an audible warning tone from a piezo buzzer, or flashes an LED for each discharge detected, giving you advance warning of impendig storms so that precautions may be observed. Presented is 68 watts LM3886 Power Amplifier with the use of popular LM3886 amplifier integrated circuit. Amplifier should be fed by source symmetrical good filtered of + 34 and – 34 volts. R2 and L1 is a resistor of 10 ohms / 2watt coiled with 10 to 12 you exhale of enameled thread AWG 20. The circuit integrated lm3886 is a component easy of being found at the electronics stores, for that he is used in several projects of potency audio, some exist circuits with linked lm3886 in bridges for power of up to 150 watts. For most information on the assembly of that circuit, I suggest that sees the datasheet of the lm3886 in the site of the national semiconductors. With the information of the leaf of data you can adapt the circuit with lm3886 your needs.

There is a great deal of old amateur gear which many amateurs have decided to restore and bring back to life. While much of the early amateur transceivers work just fine they usually lack a digital readout and must rely on analog dials for tuning. The problem of dial calibration is complicated by the non-linear effects of tuning capacitors. This month's circuit is a 100Khz crystal calibrator using an inexpensive microprocessor crystal and CMOS IC's which are readily available at Radio Shack. The main problem with building a 100Khz oscillator is the unavailability of 100Khz crystals. Even if you find a vendor willing to cut such a crystal for you, plan on paying $20 or more not including shipping charges.

The circuit uses an inexpensive 8MHz microprocessor crystal which can be easily obtained from most parts suppliers. Using a 74HCT393 binary counter IC, we can easily divide down the 8 MHz signal from our crystal into 100Khz or almost any frequency we need. Recently the RASON technical committee was hard at work at the repeater site repairing our 2 meter repeater antenna. One of the members commented to me that I should write an article about collinear arrays so that we could all build our own.

While it is not always feasible to home-brew a commercial quality antenna designed to take hurricane force winds, it is very feasible to built a collinear antenna for average use. This article describes a collinear antenna made from very inexpensive RG58/U coaxial cable and encased in PVC pipe. Before we start building we need to cover some ground about the characteristics of coaxial cable. First remember that there is something called the velocity factor for coaxial cable. For RG58/U coax it is typically.66. This means that when we calculate the length of ½ wavelength in free space we need to adjust its size by multiplying it by the velocity factory. Simply put, RF slows down by the velocity factor when traveling through coaxial cable.

All that aside now, lets calculate the ½ wavelength of RG58/U coaxial cable with a frequency of 444 Megahertz. Here's a laboratory power supply with output voltage continuously adjustable from 0 V to 24 V DC, remote voltage sense capability (Sense internal/external), output current limit is continuously adjustable from 0.04 A to 4 A and output current can be limited continuously or output shut down (Limit/cut). Remote sensing means there are two additional wires which sense the delivered voltage at the load and compensate for any voltage drop along the cables which carry the delivered current. This improves voltage regulation at the load considerably but requires two additional wires for the sensing.

A switch allows internal sensing at the output terminals for simpler operation when remote sensing is not required. I like to have a switch which lets me choose between limiting the output current continuously (useful for charging batteries), or shutting down the output if the current limit is reached (useful for protecting equipment being repaired). Another thing I like to have in the power supplies I build is a push button switch which multiplies the current scale by a factor of 10. That way one can momentarily press the button and get a much more precise reading of current.

By making the switch a push button one cannot forget to turn the function off and risk the instrument being damaged when a large current is put through it. In this case and for now I am not installing this function because I am using the instrument's shunt resistor to sense the current for the electronic control system and I would have to change several things. I might do this in the future. The power output of many transmitter circuits are very low because no power amplifier stages are incorporated.

The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres. The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts.

Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signal power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2. Here's a really simple and inexpensive Power LED driver circuit. The circuit is a 'constant current source', which means that it keeps the LED brightness constant no matter what power supply you use or surrounding environmental conditions you subject the LED's to. Or to put in another way: 'this is better than using a resistor'. It's more consistent, more efficient, and more flexible.

It's ideal for High-power LED's especially, and can be used for any number and configuration of normal or high-power LED's with any type of power supply. As a simple project, i've built the driver circuit and connected it to a high-power LED and a power-brick, making a plug-in light. Power LED's are now around $3, so this is a very inexpensive project with many uses, and you can easily change it to use more LED's, batteries, etc. Rotary encoders are very versatile input devices for microcontroller projects. They are like potentiometers expect of digital nature and unlike analogue potentiometers they never wear down. Rotary encoders not only provide 360 degrees of rotational freedom they also allow digital positioning information to be gained without the use of analogue to digital converters (ADCs).

When using rotational encoders in projects it's possible to use the same encoder to represent a number of different input types, however this requires some form of feedback display to let the user know what information he is inputting and the 'position' of the encoder. The project is based around a 24 position rotary encoder, 16 LEDs arranged in a circle around the encoder, an A6276 16 LED serial driver IC and the PIC182550 microcontroller. A rotary encoder has 3 pins usually called A, B and C.

The C pin (which is normally the centre pin) should be grounded and both A and B should be connected to the microcontroller with individual pull-up resistors on each input. In this project I used RB4 and RB5 on the PIC to connect the encoder; this has 2 advantages, firstly you can use the PORTB internal weak pull-up (which means you do not need external resistors) and also the PIC provides an 'interrupt-on-change' which can be used to monitor the encoder. As shown in the schematic, temperature sensor of our electronic thermometer is LM35DZ. There are some kinds of LM35 IC, since it is cheap and easy to find we used LM35DZ in our project.

It measures from 0°C to 100°C with a very linear output graph.For one degree change, it increases its output 10mV. On the Electronic Thermometer Schematic other hand, this circuit measures temperature values only between +10°C and +39°C. 2 numbered (middle) pin of the sensor is connected to the 5 numbered pins of LM3914 ICs. So every IC determines how many leds of bargraph will bright due to the analog signal received from the sensor. 2.2 microfarad tantal capacitors are connected between the 2 and 3 numbered pins of LM3914.

Resistors in the circuit have%1 tolerance values. This project shows how to build an Audio amplifier based on LM386 IC. The circuit is very simple and construction is easy on a breadboard. The LM386 IC is unique in that the gain can be modified by changing Resistor R2 and Capacitor C2. This configuration will give us a gain of 20. By removing R2 and connecting C2 across pins 1 and 8, we can increase the gain to 200. It is important to understand that increasing the gain does not increase the output power.

The increased gain is only used when a very low input signal is to be amplified. In a previous article I discussed building audio amplifiers using discrete transistors. While it is possible to build good audio amplifiers from discrete transistors, they are no match for the many audio amp IC's available to us. IC's offer many advantages including high efficiency, high gain, low standby current, low component count, small size and,of course, low cost. It is little wonder that audio amp IC's have replaced discrete transistors in most consumer electronic devices.

While many experimenters have stayed away from these little black mysteries, I am going to uncover some of their secrets and demonstrate how easy they are to use. Having decided to build an ultra-compact design, using a spare LM4780 seemed like an obvious plan. Having said that, I might choose a different IC if I didn't already have one to hand. The LM4780 contains two LM3886 dies (reference) giving 60 watts per channel, which is rather more than required this application. National Semiconductor make an enormous range of IC's with differing power levels and configurations, and there are plenty of possible candidates for this application - after all, we only need a few watts as this amplifier will principally be driving small speakers on the computer desk. The USB-LED-Fader is a device to control a number of LEDs via USB. I built it to display the online status of my internet connection, the recording status of my video recorder (VDR), and warnings if the available disk-space is low.

You can imagine an endless number of applications for this. The LEDs are controlled with pulse width modulation (PWM). That way, they are not only on or off, it is possible to control the brightness. Included in the device are a number of 'waveforms' that can be displayed through the LEDs. That way, one LED can display some kind of a sine- or triangular wave without any interaction with the controlling host. Every LED can be controlled individually; each one can display its own waveforms.

Build your own Special Edition Accurate LC Meter (Inductance Meter / Capacitance Meter) and start making custom made precision coils and inductors. Accurate LC Meter allows to measure incredibly small inductance making it perfect tool for making all types of RF coils and inductors. It can measure inductance starting from only 10nH - 1000nH, 1uH - 1000uH, 1mH up to 100mH and capacitance from 0.1pF up to 900nF.

Special Edition LC Meter includes top notch high precision components that are only found in premium quality kits. It includes high quality double-sided printed circuit board (PCB) with red solder mask and pre-soldered tracks for easier soldering, detachable LCD display with yellow-green LED backlight, programmed PIC16F628A microcontroller chip, high precision capacitors and inductor, 1% Metal Film resistors, Machined IC Sockets, gold plated header pins, LCD header connectors and all the other components that are needed to build a premium quality kit. Thanks to the use of LCD connectors LCD display can be detached from the main PCB board at any time even after the kit has been assembled.

All components are through-hole and are easy to solder. Special Edition Accurate LC Meter is designed for professionals that require unprecedented measurement accuracy and offers great value at low cost.

This ESR Meter is perfect for any electronics repair technicians, engineers or hobbyist. This handy ESR meter measures electrolytic capacitor equivalent series resistance (ESR) in the circuit. ESR is a very important characteristic of capacitors greater than 1 microfarad. This meter makes measurements which are often impossible to check with standard digital capacitance meters. This ESR meter is based around ICL7107, 4049, NE555 and TLC274 operational amplifier and can measure resistance from 0.01 Ohm up to 19.99 Ohm.

ESR value is displayed in Ohm on four digit LED display. The power consumption is only 8mA using 12V battery. ESR Meter offers very simple design and is easy to assemble. This tiny receiver is not much bigger than an AA cell. It is powered off two LR44 button cells, which are expensive and I assume wouldn't last terribly long.

I'll be on the lookout for LR44's at the markets and $2 shops now that I've got this radio! As with all these sorts of radios, the headphone lead functions as the aerial.

Supplied with this receiver were a pair of those awful 'in-the-ear' type of miniature type earphones. Apart from the appalling sound quality, they are insensitive, unhygenic and dirty, fragile, and do not block out external sounds. So, I use the normal kind of headphones instead. The enclosure is all clipped together, and once I'd opened it, sure enough, a TDA7088T was visible. The audio amp appears to be one transistor; ie. Single ended class A. I don't know what current it's drawing so I can't say whether it's consuming much more battery current than a class B amp would.

In any case I would prefer AAA cells rather than the LR44's. The circuit will limit the current through the supply wires to 5.5A for about 1.5sec. After that time the relay will close and the current flow won't be restricted anymore. This is a very interesting circuit if you have a large toroid with big electrolytic caps connected to the power supply, since these will act like short circuits for a small amount of time if they start charging.

This unit is a delay unit that can be connected directly to the mains power supply. It´s not obligatory to use one but it is a good idea, specially if you have a big toroidal transformer larger than 300 VA. This unit has a delay circuit and for the delayed time the mains power is supplied through power resistors minimizing in this way the big inrush current due to big capacitors and big toroidal transformers in the power supply. When everything is stable it shorts the power resistors and supplies the mains power directly. This project is a FM Radio based on TDA7000 and LM386 integrated circuits. What is unusual about TDA7000 IC is how it operates.

It is a proper FM superhet receiver, with the usual local oscillator, mixer, IF amplifier, limiter, and phase detector. The difference is that there's only one tuned circuit; the local oscillator. Like the Pulse Counting Receiver, the TDA7000 relies on a low IF so that ordinary Op Amp circuitry can take care of the gain and bandpass characteristics. Only 70Kc/s is used with the TDA7000.

Now, you might remember that the deviation of a broadcast FM signal is +/- 75Kc/s. A fully modulated signal would therefore sound rather distorted.

So, how can this IC work? It's quite simple in that there is what Philips call a Frequency Locked Loop. Basically, the local oscillator is shifted in response to detector output so that the bandwidth of the mixer output is never more than +/- 15Kc/s.

It is actually compressing the frequency range of the modulated signal. The muting or squelch feature is novel to say the least. Although it performs as any other muting circuit does, the TDA7000 provides an artificial noise generator so that the receiver still sounds alive while tuned off station. If you don't need that feature, just remove the.022uF condenser at pin 3. Not all Philips data sheets show it, but connecting a 10K resistor from the supply to pin 1 will disable the squelch. This is 8W Class A Amplifier I recently built.

I am very pleased with the sonic results of this amplifier. It really does not disappoint. Even using fairly standard 3 way speakers in a large room, surprisingly there is ample power. What strikes me the most is the ability of this amplifier to differentiate between instruments and noises in the sound stage. This clarity is what I like most and I think this is achieved by deceptively simple and pure circuit topology. I used the original board layout, transistors and JFETs, and made some modifications. Heat sinking was increased to approximately triple the amount recommended.

Instead of using the standard bridge rectifier, capacitor bank and battery setup, I opted for a fully regulated supply with a total of 127,0000 uF capacitance per channel and a 500 VA toroid transformer. This is a solar panel battery charger schematic for AA and AAA rechargeable batteries. A small solar panel would be very good as a source of voltage charger.

Building a solar AA battery charger only requires a few components and a simple construction. Solar panels should be well adapted to the battery to be charged or the battery may be overcharged. If you want to charge batteries with different capacities, then you need to change the solar panels. Since this is a simple solar battery charger that does not automatically turn off when the battery is full.

So we need to maintain the charging current is low enough that will not damage the battery even when they are fully charged. An LM317T voltage regulator chip that can be used with a suitable resistor to regulate current.

See solar AA battery charger. A simple light / dark activated relay switch circuit, suitable for many applications like the automatic switching of the lights in a shop window or a room according to the ambient light level. The circuit uses a light dependent resistor (LDR). A light/dark option has been incorporated. The term 'light/dark' is used because the circuit has a PCB-mounted switch on board. In one switch position a light-to-dark transition will activate the relay. In the other position a dark-to-light transition is required.

So you can use the falling light on the detector to switch on a normally off circuit or switch off a normally on circuit. The relay is on when LDR uncovered and relay off when LDR covered.

Adjust VR1 for light sensitivity. LED will turn on at the same time with relay. This circuit detects the dial tone from a telephone line and decodes the keypad pressed on the remote telephone.

The dial tone we heard when we pick up the phone set is call Dual Tone Multi-Frequency, DTMF in short. The name was given because the tone that we heard over the phone is actually make up of two distinct frequency tone, hence the name dual tone. The DTMF tone is a form of one way communication between the dialer and the telephone exchange. A complete communication consist of the tone generator and the tone decoder.

In this article, we are use the IC MT8870DE, the main component to decode the input dial tone to 5 digital output. These digital bits can be interface to a computer or microcontroller for further application eg. Remote control, phone line transfer operation, LEDs, etc. Randall converted an Arduino into AVR chip programming hardware for use with AVRDude. The project programs AVR tiny13 and other tiny AVR chips using an Arduino. He provides code and instructions to implement the Atmel AVR910 In System Programming protocol.

I ported the Atmel AVR910 In System Programmer protocol to the Arduino. Now I can write programs to my ATtiny2313 and tiny13 chips. The Arduino sketch is available for download here. It works with the AVRDude programming software.

This article will show how to use the Arduino to upload a program to the tiny13. The first step is to download the zip, extract the.pde file, then load it into the Arduino IDE, and write it to the Arduino. Next we can hook up the tiny13 chip.

This fm rf amplifier uses 2SC1971 transistor to provide 5 watts of output. Output matching is adjusted via the two 40pF trimmer capacitors likewise also to the input.

Note that the emitter of this transistor is directly grounded on the heat sink and should have a good thermal transfer. Driving power of 100 to 200mW can be applied in order to provide 5watts of output. Use a dummy load to tune this amplifier and remember that the transistor is biased in Class C, sufficient filtering should be followed after the output to minimize all the harmonics. Use ground plane construction technique in the PCB lay-out for best result, the more the grounding the better. If you have hard time finding the 10uH rf choke, try to wind 1/2 meter of 0.2mm enamel wire over a 33K 1/2 watt resistor and solder the coil ends to the legs of the resistor.

This is a very simple and easy to build programmer for Atmel microcontrollers from AVR family. The microcontrollers must support serial programming.

This programmer is connected to a PC through the RS232 serial interface and can be used with the PonyProg or Avrdude software programmer. The programmer is quite simple and it is based on the SI-Prog from the author of PonyProg software. The Zener diodes D2, D3 with the resistors R2, R3 reduce the voltage from the ouput pins DTR, RTS on the serial port to around 5V which is suitable for microcontroller (MOSI, SCK). MISO signal is connected directly to the input CTS pin.

The Zener diode D1 with the resistor R1 drive the NPN transistor T1, which controls RESET signal. The AVR microcontrollers are in reset when the signal has low level. The resistor R5 works as a pull-up for reset signal. The resistor R4 helps to close the transistor T1. The programmer has standard 10 pins header. Presented here is a low-power FM transmitter with varactor diode tuning using surface-mount devices (SMD) that will be received with a standard FM radio.

Soldering surface mounted devices is not so hard and actually is quite easy. There are many designs for small FM transmitters but they have some problems. First, you need an audio amplifier to get enough modulation. Second, the antenna is attached directly to the collector.

Third, the coil L must be wound by hand and adjusted by stretching. It all ads with a weak signal that tends to drift in frequency. In contrast the transmitter schematic we present here eliminates some of those problems, using varactor diode for tuning and modulation, givin great sensitivity without an audio amplifier. This particular transmitter was later shipped up to VY1JA in the Yukon where, thanks to Jay's excellent antenna system, it was heard in Europe as well as in New Zealand during one of the Trans-Pacific Tests! Running 24 volts on the final will produce 100 watts into a 50 ohm load.

The transmitter utilizes a 4060 binary counter IC chip as both the crystal oscillator and frequency divider. I used a 2200 kHz crystal along with the 'divide-by' sixteen output to produce a signal at 137.5 kHz.

Other combinations of crystal frequencies and 'divide-by' combinations may also be used since the 4060 features divided outputs for f/32 (pin 5) and f/64 (pin 4), among others. You may have a 4MHz crystal or an 8MHz crystal in your junk box that will put you in the band using these output pins.

This IR remote control that you can use to control other devices or circuits up to 8 devices. The control codes are sent in RC5 format modulated to about 38 kHz carrier frequency.The IR transmitter powered by the CR2016 which is a 3V button Cells Battery CR2016. Strong Digital Tv Srt 100 Usb Driver here. To extend the life of the battery this is done by putting the CPU into SLEEP mode for most of the time and wake-up only when a key is pressed. PIC16F630 is the heart of the transmitter used to send IR command to receiver.It also generate 38KHz carrier frequency.The CR2016 is 3V battery which is supply for the circuit. When any key not pressed the CPU work in SLEEP mode to reduce baterry power consumption and wake-up only when any key pressed. To wake-up the CPU from SLEEP mode the CPU use interrupt on change feature which interrupted when the state on PORTA change then the program execution after an interrupt is at the interrupt vector, if the global interrupt is not enabled, the program starts executing the first line of code right after the SLEEP instruction.In the interrupt service routine the software will scan the key that pressed and send IR command appropriate with key pressed. This is a 8 channel RF remote control project.

The transmitter powered by 5V.the RF module I used had long start-up and power down period after receiving a high pulse. To counter all of this I kept the receiver in constant standby mode, but sending a information all the time. That way the noise is flooded out, and the receiver will always respond. I had been trying all sorts of error detection methods and different ways of encoding the bytes, when I just gave up. Since the link is so noisy I decided to cut out all of the error detection methods and just make it accept anything it receives, and see what happened from there.

But what do you know, it worked! This is a DC power supply circuit using the LM317T voltage regulator IC, which is the IC of this type is very popular among electronics hobby. Parameter to regulate the output DC voltage carried by the LM317 circuit with a maximum current of 1A. LM317 output voltage of this circuit is 6V DC, source from the stress out of the 12V CT AC transformer, and then converted to DC half-wave voltage by diodes D1-D2, and filtered by C1 capacitor. The transformer is used should be about 1-2A. Output voltage of 6V DC power supply circuit is determined by the value of R1 and R2.

Diodes D3-D4 on the LM317 voltage current circuit to protect poor return for LM317 circuit IC. As for the other capacitors C3-C4 is used to refine the output voltage, and complete power supply circuits. 'ESR' stands for equivalent series resistance. ESR is one of the characteristics that defines the performance of an electrolytic capacitor.

Low ESR is highly desirable in a capacitor as any ripple current through the capacitor causes the capacitor to heat up due to the resistive loses. This heating accelerates the demise of the capacitor by drying out the electrolyte at an ever increasing rate. Over the lifetime of a capacitor, it is not uncommon for the ESR to increase by a factor of 10 to 30 times or even go open c.