New Circuits Page 242
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The purpose of this circuit is to animate shop-windows by means of a capacitive sensor placed behind a post-card-like banner. The card is placed against the glass inside the shop-window, and the visitor can activate the relay placing his hand on the card,....
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When testing circuits with a logic probe, it is sometimes difficult to watch the LEDS on the probe to determine the logic state. With this probe the logic states are audible. This probe is designed for TTL circuits only but could be modified for CMOS. The....
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This circuit for a test set contains a signal injector (U1A/U1B) and associated com..
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The Miller solar engine uses a 1381* voltage detector (a.k.a., a voltage supervisor) IC to drive a voltage-based (type 1) solar engine. The 1381 is normally used to reset CPUs and Micros when the power supply drops too low for reliable operation. So 1381s....
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The IRPLLNR1 is a high efficiency, high
power factor, non-dimmable electronic ballast
designed for linear fluorescent lamp types.
The design contains an active power factor
correction circuit for universal voltage input
and a ballast control circuit....
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Any dc voltage source in the 2- to 15-V range can be chopped into a unipolar square wave that has a peak amplitude nearly equal to the dc source voltage-with circuit (lightly loaded CMOS will swing within a few millivolts of each rail at low frequencies).....
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The speed-control switch offers reasonably good control and stability to both ends of its operating range. This circuit uses two SCR devices in a full-wave configuration to control the dc power to a motor. ..
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This circuit converts frequency to voltage by taking the average dc value of the pulses from the 74121 monostable multivibrator. The one shot is triggered by the positive-going ac signal at the input of the 529 comparator. The amplifier acts as a dc filter,....
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This frequency/voltage converter enables calibrations of cassette-deck speed. It records a steady 1-kHz ton..
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The classic state-variable (two-integrator) filter (see Fig. A) is famous for its insensitivity to device parameter tolerances, as well as its ability to provide three simultaneous separate outputs: high pass, bandpass, and low pass. These advantages often....
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This preamplifier has a built-in regeneration control boost gain selectivity. CI is a single or multi-gang AM broadcast-band tuning capacitor. LI is a ferrite loop antenna, tapped at about 15 to 25% of total turns. This circuit should prove useful for....
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The GainClone idea seem to have taken off in a fairly big way. There are some good reasons for this, and I found myself in the position where SWMBO (she who must be obeyed) was getting very twitchy as I added amps and speakers to `her` room (which is....
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Note first the battery to be treated at the center of the figure. It is connected to contacts of a relay. The diagram shows the relay at rest. Under these conditions the battery is in SHOCK . His pole - is grounded and its positive pole to the circuit of....
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This zero-crossing detector uses a dual LM393 comparator, and easily controls hysteresis by the reference levels which are set on the comparator inputs. The circuit illustrated is powered by +10-V power supplies. The input signal can be an ac signal level up....
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Detector uses three sections of an L144 and a CMOS NAND gate to make a very low power voltage monitor. The 1 MO resistors Rl, R2, R3, and R4 translate the bipolar ±10 V swing of the op amps to a 0 to 10 V swing acceptable to the ground-referenced CMOS logic..
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This is the basic interface I used as part of my Computerized Room project. This is the parallel interface only. The 8 bit input card can be found, along with the rest of the project, at Computerize Your Room/House. This interface, as well as the other two....
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The circuit in Figure 1 shows a method of meeting this challenge with 100% margin. In other words, it presents approximately 10-M leakage resistance across the line. The basic relaxation oscillator has the LED of an optoisolator in the discharge path of the....
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For frequencies below 20 MHz, a fundamental-frequency crystal can be used and the resonant tank is no longer required. Also, at this lower frequency range the typical MECL 10,000 propagation delay of 2 ns becomes small compared to the period of....
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The design of battery-powered equipment can often be
quite challenging. Since few ICs can operate directly from
the end-of-life voltage from a 2-cell battery (about 1.8V),
most systems require a DC/DC converter. The system
designer often has a limited....
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Snubber circuit R2C2, as shown, might be necessary since Rl and Cl are tailored for optimized triggering and not for dV!dt protection. Fiber-optic pairs can be used with discrete SCRs to switch thousands of volts. A photon coupler with a transistor output....
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Most ATV (Amateur Television) transmitters transmit a DSB signal and commercial television stations use a VSB (Vestigial Sideband) signal. This fact is made use of in this converter to use the lower sideband. This results in less interference from repeaters....
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This page shows three circuits for using the 555 timer IC as a photocell controlled train detector.
The circuit is shown driving light emitting diodes but any load of less than 200 milliamps could be used.
Shown on the schematic is a secondary....
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A single monostable multivibrator delays a pulse train by a variable amount; nonetheless, this amount can be no less than the minimum allowed pulse width fw· The exclusive-OR gate, IC1, generates a short pulse following every leading or falling edge of....
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The proliferation of industrial and computerized equipment containing programmable memory has increased the need for reliable recording media. The magnetic tape medium is presently one of the most widely used methods. The primary component of any magnetic....
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The Testatika design based on the Pidgeon/Wimshurst machine is of course only one type of electrostatic generator to build this system around. Since the early 1900s such power generators have come a long way in sophistication - and in power output - recently....
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Most cards of sound in computer, are deprived stereo input for microphone, on the contrary have stereo input for high level [ Line ]. The circuit uses the input Line of card of sound, in order to we place a two mono stereo microphone, in the input of card of....
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A single hand clap will be picked up by the electric mic which is coupled through C1 into the op amp IC1. The output of IC1 triggers the 555 IC timer IC2 which is configured as a monostable multivibrater. The trigger pulse is stretched by IC2 and outputs a....
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The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz.
The circuit's operation can be explained as follows:
When....
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Full short-circuit and overcurrent protection is given by this circuit suitable for workbench applications in technical schools and laboratories where there is a need to work directly with the mains. Additional features are a clearly visible red lamp....
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This circuit uses a tricolor LED display to indicate acceptable and unacceptable output voltages. One to set the upper voltage limit, the other, the lower voltage limit. When the monitored voltage is above the set maximum, the LED display turns red. Yellow....
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Since I implemented a D type flip flop using the PIC Logic Elements I thought I might go the other way and implement an entire D type flip flop in a single PIC. This uses the edge triggered and port change status interrupts and was an opportunity to have a....
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The circuit shown will convert logic level voltages to and from RS232 serial voltages levels.
For basic serial comms between a Microchip PIC and a PC or other device you generally only need to connect the Gnd, Txd and Rxd lines.
This little circuit....
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When the brake pedal is on depressed, battery positive voltage normally applies through the STOP fuse and stop light switch to terminal STP of the ECU, and the ECU turns the cruise control off. A failsafe function is provided so that cancel functions....
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A three-dimensional surround sound Ambisonic recording can be captured using a tetrahedrally arranged quartet of cardioid pattern microphone capsules connected to some simple circuitry to convert the outputs to a standard B-format signal. B-format signals....
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PBUS is an RS485-like multi-drop bus for interconnecting PIC and other microcontroller-driven devices. Protocol and software is written by Jap. Just include a separate pbus library file into your project and add your command handlers for the specific device....
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The delay time for all circuits shown has been revised. The optimum is around 100ms - sufficient for around 5 full cycles at 50Hz, or 6 cycles at 60Hz. It is also quite alright to run the transformer to around 200-500% of full load current at start-up, and....
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Described here is a very inexpensive solution to many phono-controlled applications like remote switching on, for instance, or activating a camera, tape recorder, burglar alarms, toys, etc. The circuit given here employs a condenser microphone as the....
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It still uses a transistor to do some switching, and it still needs a pair of diodes and capacitors, as would be used in a conventional multiplier, but it doesn't require a steady stream of pulses and the output voltage is set by a resistor divider as the....
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A programmable code lock can be used for numerous applications in which access to an article/gadget is to be restricted to a limited number of persons. Here is yet another circuit of a code lock employing mainly the CMOS ICs and thumbwheel switches (TWS)....
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A block pinout diagram of the LS7220 keyless-lock IC is shown. The keypad must provide each key with a contact to a common connection. In this case, the common connection goes to the positive supply rail so that when a key is pressed, a positive voltage is....
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The signal output by the radio control receiver is a form of PWM. This may be useful for driving servos, but is inconvenient for general electronic applications. Therefore, several of the circuits on this site convert this signal into a voltage first. This....
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This circuit produces 5- to 25-V output to drive a VCO from a standard ± 15-V supply system. R7 and CI supply fr..
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without significant added complexity, and a natural tendency to run away under no-load (high Q) conditions. The 20-kHz control circuit (see Fig. 2) overcomes these shortcomings hy feeding back into the asymmetrical thyristor trigger pulse generators (see....
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This circuit is a powerful video sender in VHF band. The modulator section is designed to operate on either channels 7 to 13 or 14 to 29. For channels 7 to 13, L1 and L2 are 3 turns of #22 wire wound on a 3/16 inch form. For channels 14 to 29, L1 and L2 are....
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A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017s first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that the IC normally delivers.....
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The circuit of automatic emergency light presented here has the following features: 1. When the mains supply (230V AC) is available, it charges a 12V battery up to 13.5V and then the battery is disconnected from the charging section. 2. When the battery....
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This was one of my very first transceiver developments. This page was also one of the very first circuit descriptions that I put on the internet quite some years agon. Today I would not build a transceiver like I did then, but it was working, so I have kept....
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The Nora K5W is a German radio from about 1929/1930.
Is uses the tubes: 2x REN804, 2x REN1004, RE134 or RE604, RGN1054...
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The LM317 is capable of providing extremely good load
regulation, but a few precautions are needed to obtain
maximum performance. For best performance, the
programming resistor (R1) should be connected as close to
the regulator as possible to minimize....
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By selecting capacitors, various voltages can be obtained from this supply. Notice that C2 through C7 must be ..
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Supervisory circuits normally monitor a microprocessor`s supply voltage, asserting reset to the IC during power-up, power-down, and brownout. In this way, the circuit ensures that the supply voltage is stable before the microprocessor boots, thus preventing....
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One-farad capacitors require some care. It`s a common knowledge that they must be pre-charged with a current-limiting resistor before plugging in. It is less common knowledge that those fifty-dollar `smart cap controllers` are in fact very simple devices,....
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This circuit when used with a 555 timer will cause light emitting diodes to turn on and off more slowly. This will make the LEDs appear similar to incandescent lamps...
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The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These IC`s are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but....
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This Adjustable Strobe Light is the bigger brother of the plain old strobe light. This one uses a much more powerful "horse shoe" Xenon tube which produces more light. You can also control the flash rate up to about 20Hz. Do not look directly at the flash....
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This relatively simple mixer was designed for three dynamic microphones, but can be re-designed for more or less. Level and tone controls are available to tailor the sound to your needs...
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Only one out of 9,999 possible codes has the power to unlock this simple, yet effective, electronic lock. A combination lock is not just a perfect system to protect your belongings, it is also a valid system to let everyone to know that you are vigilant: an....
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This design is based on one published by Milan Lulic in the German magazine elektroModell. Mr. Lulic`s design is for surface mount technology (SMT) construction, whereas mine uses standard off-the-shelf components, and is therefore better suited to....
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This amplifier functions over a wide range of gains, typically 1-10. It combines the LT1010 and a fast discrete stage with an LT1008 based de stabilizing loop. Q1 and Q2 form a differential stage which single-ends into the LT1010. The circuit delivers 1 V....
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By utilizing both halves of a dual timer it is possible to obtain sequential timing. By connecting the output of the first half to the input of the second half via a 01 µF coupling capacitor sequential timing may be obtained. Delay ti is determined by the....
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The amplifier is capable of delivering around 1.5W into 8 ohm headphones, and 2.2W into 32 ohms - this is vastly more than will ever be needed in practice. The use of a 120 Ohm output resistor is recommended, as this is supposed to be the standard source....
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Vinyl equalisation (EQ) has been with us in a stable and predictable form for quite a long time, but for those who are interested in the old 78 rpm records there are a great many problems to overcome. One of these is obtaining a turntable that runs at 78....
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Before World War II the FM radio band was just below 50 Mc. Read all about it. If you have such a radio, you might want to build this converter. It will let your old set receive the modern FM band (88 to 108 Mc.). This design is based on an article I....
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The fixed voltage power supply is useful in applications where an adjustable output is not required. This supply is simple, but very flexable as the voltage it outputs is dependant only on the regulator and transformer you choose. The maximum output current....
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This circuit will emit an intermittent beep (or will flash a LED) when the water contained into a recipient has reached the desired level. It should be mounted on top of the recipient (e.g. a plastic tank) by means of two crocodile clips, acting also as....
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The circuit forces a current to build up in the L1 coil and the LEDs until the voltage developed across R3 reaches VFB/3.3V. At this point, power switch Q1 turns off, and the magnetizing current keeps circulating in the coil and LEDs, thanks to....
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Using two gates from a CMOS 4011 NAND chip, a simple aquarewave oscillator can br made. Alternatively a CMOS 4001 chip can also be used, or a TTL equivalent. In this circuit the mark space ratio can also be independantly controlled by varying the value of....
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This circuit was used to trip a camera shutter. Grounding pin 2 of U1 makes pin 4 of U1 go high. This triggers both tim..
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A simple boost circuit that gives 30 volts pk/pk output using a 9 volt battery. The addition of a Ge diode bridge makes a surprisingly good octave box...
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This revision reduced the signal level and
treble response in the preamp for a smoother
sound in both cathode and fixed bias modes.
The power supply was also revised for lower
B+ voltages to the EL84 plates. "This amp was built on the chassis of an....
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Room temperature plays a vital role in determining human thermal comfort. This digital thermometer is designed to measure room temperature and display it on a LCD screen in both Celsius and Fahrenheit scales. A PIC16F688 microchip is used as the main....
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Power is applied to the circuit with the initiate switch open. The 25-JtF capacitor charges through the A14, or equivalent, diode and 2.2-KO resistor to full supply voltage. When the initiate switch is closed, the low side of the capacitor is suddenly....
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This project is not to introduce Tic Tac Toe. Everyone knows this game.
It`s to introduce two features. Bi-coloured LEDs, microcontrollers and the skill of writing an ALGORITHM.
You can use the project to learn the skills of creating the Tic Tac Toe....
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This system contains an IR transmitter, an IR receiver/RF transmitter, and an RF receiver/alert beeper. Two IR ..
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At half brightness, the lamp current is pulsed on and off (Fig. 50-12b) by the voltage developed across the resistor and capacitor at the current-sense output. Lamp current is sensed by the current-sense output. A simple pulse-width modulation....
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Many of today`s designs use low-cost microcontrollers from Freescale and Microchip, but during the last decade, device packages have resorted to ever-smaller footprints featuring as few as eight or even six pins. Although these packages minimize pc-board....
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The circuit comprises two sections: charger power supply and LED driver.The charger power supply section is
built around 3-terminal adjustable regulator (IC1) LM317, while the LED driver section is built around transistor BD140(T2). In the charger power....
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This circuit (the Bucciarelli one) is designed to sense a sudden increase in light and does so extremely well. A few of these were actually built and tested and found to not trigger from normal room light. They sometimes malfunctioned if the phototransistors....
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This switch reacts to the touch of a finger to turn lights and/or appliances on or off. The device uses the human body as an..
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The circuit accepts two positive-voltage inputs VN and Vv and provides a TTL-compatible output pulse train whose repetition mte is proportional to the ratio VN/ V0. Full-scale output frequency is about 100 Hz, and linearity error is below 0.5 percent. The....
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This circuit turns a sine wave into a square wave. It is comprised of a single 2-input NAND Schmitt trigger that`s configured as an inverter with a trigger level adjustment at its input. As the input voltage rises above the gate`s trigger point,..
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This jam circuit can be used in quiz contests wherein any par- ticipant who presses his button (switch) before the other contestants, gets the first chance to answer a question. The circuit given here permits up to eight contestants with each one allotted a....
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Here"s an interesting mixer circuit. With it you can effectively combine signals from audio to high-fre-quency RF. Als..
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The circuit spectator interference enables implantation mono sound at any point between stereo speakers. When P1 is in the middle of his journey, there is strengthening or weakening of the mark the entrance to the exit in any of the two channels. When the....
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Loop Antennas are considered to be "samall" when their diameter drops below about 1/10 of the wavelength they are intended to be used at. In this case, I use the term "Tiny" because the antenna's diameter is about 1/30,000 the wavelength, and at 5.5 cm in....
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This is a special low voltage version of my audio preamp. T1`s emitter voltage is biased close to half supply voltage (1.5V) to allow for maximum output voltage swing. Both transistors are direct coupled and have closed loop feedback to aid temperature....
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I have no idea whether the RCA 40468A FET is still available or not. It came in a 4 pin metal can - with the 4th pin connected to the substrate. I have successfully substituted other N-channel devices, such as the HEP-802 - which comes in a plastic TO-92....
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In the circuit shown below, if the voltage at the output terminals rises above 6.2V, zener conducts charging capacitor C4. This voltage will fire the silicon-controlled rectifier (SCR), which quickly shorts-or puts a ?crowbar? ? across the supply rails....
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Many countries have 115 volts mains supplies. This can be a problem if your electric shaver is designed for 220/240 volts only. This simple rectifier voltage doubler enables motor driven 240 volt shavers to be operated at full speed from a 115 volt supply.....
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The circuit, is based on a commercial temperature sensor (TS6178) and an MC3334P ignition chip, When the radiator temperature increases, the sensor pulls the base of Q2 low via Ql, which is wired as a diode. Q2`s collector thus goes high and triggers IC1,..
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A bit-error-rate (BER) tester is a basic tool for digital-communications measurements. Although many commercial BER testers are available, you can easily design and build an inexpensive version. The scheme in Figure 1 has performance similar to that of a....
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I keep all rights to those circuits myself. You may freely build those circuits to yourself and your friends, but commercial use of those circuits is not allowed. NOTE: Those circuits are old designs from time when I was not so good in electronics than I am....
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The Atmel AVR series are very good microcontrollers with quite a rich instruction set, rich enough that lots of folks have good compilers for them so we don`t have to learn their assembler. A very rich compiler available is the BASCOM/AVR compiler from MCS....
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Very little extra circuitry is needed to do both forword and backword walking sequences along with a few other tricks. The PIC16F818 has a lot of features that work well in this situation. As you can see from the Schematic and Source Listing, position....
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Transmitter operation. Operating power for the transmitter circuit is derived directly from the ac line. The dc power to operate the circuit is generated in two stages, one for an RF power-am-plifier stage, and the second for the remainder of the circuit.....
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One small spot of rain on the sense pad of this bleeper will start this audio warning. It can also be operated by rising water. The circuit has two transistors, with feedback via capacitor Cl, but Trl cannot operate as long as the moisture sense pad is dry. ..
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For normal use it`s necessary to connect the battery, when the jumper is connected.
Please take care, that the transmitter is on and the throttle is set to "power off"...
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SPICE is the most commonly used analog circuit simulator today and is enormously important for the electronics industry. SPICE is a general purpose analog simulator which contains models for most circuit elements and can handle complex nonlinear circuits.....
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The AY-3-8910/8912 is a register oriented Programmable Sound Generator (PSG). Communication between the processor and the PSG is based on the concept of memory-mapped I/O. Control commands are issued to the PSG by writing to 16 memory-mapped registers. Each....
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This is simple almost beyond belief for distortion devices. Two transistors, four resistors, three capacitors, and two controls make all that tone. The first transistor is set up with the simplest of arrangements - input through a DC blocking capacitor....
The purpose of this circuit is to animate shop-windows by means of a capacitive sensor placed behind a post-card-like banner. The card is placed against the glass inside the shop-window, and the visitor can activate the relay placing his hand on the card,....
When testing circuits with a logic probe, it is sometimes difficult to watch the LEDS on the probe to determine the logic state. With this probe the logic states are audible. This probe is designed for TTL circuits only but could be modified for CMOS. The....
This circuit for a test set contains a signal injector (U1A/U1B) and associated com..
The Miller solar engine uses a 1381* voltage detector (a.k.a., a voltage supervisor) IC to drive a voltage-based (type 1) solar engine. The 1381 is normally used to reset CPUs and Micros when the power supply drops too low for reliable operation. So 1381s....
The IRPLLNR1 is a high efficiency, high power factor, non-dimmable electronic ballast designed for linear fluorescent lamp types. The design contains an active power factor correction circuit for universal voltage input and a ballast control circuit....
Any dc voltage source in the 2- to 15-V range can be chopped into a unipolar square wave that has a peak amplitude nearly equal to the dc source voltage-with circuit (lightly loaded CMOS will swing within a few millivolts of each rail at low frequencies).....
The speed-control switch offers reasonably good control and stability to both ends of its operating range. This circuit uses two SCR devices in a full-wave configuration to control the dc power to a motor. ..
This circuit converts frequency to voltage by taking the average dc value of the pulses from the 74121 monostable multivibrator. The one shot is triggered by the positive-going ac signal at the input of the 529 comparator. The amplifier acts as a dc filter,....
This frequency/voltage converter enables calibrations of cassette-deck speed. It records a steady 1-kHz ton..
The classic state-variable (two-integrator) filter (see Fig. A) is famous for its insensitivity to device parameter tolerances, as well as its ability to provide three simultaneous separate outputs: high pass, bandpass, and low pass. These advantages often....
This preamplifier has a built-in regeneration control boost gain selectivity. CI is a single or multi-gang AM broadcast-band tuning capacitor. LI is a ferrite loop antenna, tapped at about 15 to 25% of total turns. This circuit should prove useful for....
The GainClone idea seem to have taken off in a fairly big way. There are some good reasons for this, and I found myself in the position where SWMBO (she who must be obeyed) was getting very twitchy as I added amps and speakers to `her` room (which is....
Note first the battery to be treated at the center of the figure. It is connected to contacts of a relay. The diagram shows the relay at rest. Under these conditions the battery is in SHOCK . His pole - is grounded and its positive pole to the circuit of....
This zero-crossing detector uses a dual LM393 comparator, and easily controls hysteresis by the reference levels which are set on the comparator inputs. The circuit illustrated is powered by +10-V power supplies. The input signal can be an ac signal level up....
Detector uses three sections of an L144 and a CMOS NAND gate to make a very low power voltage monitor. The 1 MO resistors Rl, R2, R3, and R4 translate the bipolar ±10 V swing of the op amps to a 0 to 10 V swing acceptable to the ground-referenced CMOS logic..
This is the basic interface I used as part of my Computerized Room project. This is the parallel interface only. The 8 bit input card can be found, along with the rest of the project, at Computerize Your Room/House. This interface, as well as the other two....
For frequencies below 20 MHz, a fundamental-frequency crystal can be used and the resonant tank is no longer required. Also, at this lower frequency range the typical MECL 10,000 propagation delay of 2 ns becomes small compared to the period of....
Snubber circuit R2C2, as shown, might be necessary since Rl and Cl are tailored for optimized triggering and not for dV!dt protection. Fiber-optic pairs can be used with discrete SCRs to switch thousands of volts. A photon coupler with a transistor output....
Most ATV (Amateur Television) transmitters transmit a DSB signal and commercial television stations use a VSB (Vestigial Sideband) signal. This fact is made use of in this converter to use the lower sideband. This results in less interference from repeaters....
This page shows three circuits for using the 555 timer IC as a photocell controlled train detector. The circuit is shown driving light emitting diodes but any load of less than 200 milliamps could be used. Shown on the schematic is a secondary....
A single monostable multivibrator delays a pulse train by a variable amount; nonetheless, this amount can be no less than the minimum allowed pulse width fw· The exclusive-OR gate, IC1, generates a short pulse following every leading or falling edge of....
The proliferation of industrial and computerized equipment containing programmable memory has increased the need for reliable recording media. The magnetic tape medium is presently one of the most widely used methods. The primary component of any magnetic....
The Testatika design based on the Pidgeon/Wimshurst machine is of course only one type of electrostatic generator to build this system around. Since the early 1900s such power generators have come a long way in sophistication - and in power output - recently....
Most cards of sound in computer, are deprived stereo input for microphone, on the contrary have stereo input for high level [ Line ]. The circuit uses the input Line of card of sound, in order to we place a two mono stereo microphone, in the input of card of....
A single hand clap will be picked up by the electric mic which is coupled through C1 into the op amp IC1. The output of IC1 triggers the 555 IC timer IC2 which is configured as a monostable multivibrater. The trigger pulse is stretched by IC2 and outputs a....
The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz. The circuit's operation can be explained as follows: When....
Full short-circuit and overcurrent protection is given by this circuit suitable for workbench applications in technical schools and laboratories where there is a need to work directly with the mains. Additional features are a clearly visible red lamp....
This circuit uses a tricolor LED display to indicate acceptable and unacceptable output voltages. One to set the upper voltage limit, the other, the lower voltage limit. When the monitored voltage is above the set maximum, the LED display turns red. Yellow....
When the brake pedal is on depressed, battery positive voltage normally applies through the STOP fuse and stop light switch to terminal STP of the ECU, and the ECU turns the cruise control off. A failsafe function is provided so that cancel functions....
A three-dimensional surround sound Ambisonic recording can be captured using a tetrahedrally arranged quartet of cardioid pattern microphone capsules connected to some simple circuitry to convert the outputs to a standard B-format signal. B-format signals....
PBUS is an RS485-like multi-drop bus for interconnecting PIC and other microcontroller-driven devices. Protocol and software is written by Jap. Just include a separate pbus library file into your project and add your command handlers for the specific device....
The delay time for all circuits shown has been revised. The optimum is around 100ms - sufficient for around 5 full cycles at 50Hz, or 6 cycles at 60Hz. It is also quite alright to run the transformer to around 200-500% of full load current at start-up, and....
Described here is a very inexpensive solution to many phono-controlled applications like remote switching on, for instance, or activating a camera, tape recorder, burglar alarms, toys, etc. The circuit given here employs a condenser microphone as the....
It still uses a transistor to do some switching, and it still needs a pair of diodes and capacitors, as would be used in a conventional multiplier, but it doesn't require a steady stream of pulses and the output voltage is set by a resistor divider as the....
A programmable code lock can be used for numerous applications in which access to an article/gadget is to be restricted to a limited number of persons. Here is yet another circuit of a code lock employing mainly the CMOS ICs and thumbwheel switches (TWS)....
A block pinout diagram of the LS7220 keyless-lock IC is shown. The keypad must provide each key with a contact to a common connection. In this case, the common connection goes to the positive supply rail so that when a key is pressed, a positive voltage is....
This circuit produces 5- to 25-V output to drive a VCO from a standard ± 15-V supply system. R7 and CI supply fr..
without significant added complexity, and a natural tendency to run away under no-load (high Q) conditions. The 20-kHz control circuit (see Fig. 2) overcomes these shortcomings hy feeding back into the asymmetrical thyristor trigger pulse generators (see....
This circuit is a powerful video sender in VHF band. The modulator section is designed to operate on either channels 7 to 13 or 14 to 29. For channels 7 to 13, L1 and L2 are 3 turns of #22 wire wound on a 3/16 inch form. For channels 14 to 29, L1 and L2 are....
A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017s first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that the IC normally delivers.....
The circuit of automatic emergency light presented here has the following features: 1. When the mains supply (230V AC) is available, it charges a 12V battery up to 13.5V and then the battery is disconnected from the charging section. 2. When the battery....
This was one of my very first transceiver developments. This page was also one of the very first circuit descriptions that I put on the internet quite some years agon. Today I would not build a transceiver like I did then, but it was working, so I have kept....
The Nora K5W is a German radio from about 1929/1930. Is uses the tubes: 2x REN804, 2x REN1004, RE134 or RE604, RGN1054...
The LM317 is capable of providing extremely good load regulation, but a few precautions are needed to obtain maximum performance. For best performance, the programming resistor (R1) should be connected as close to the regulator as possible to minimize....
By selecting capacitors, various voltages can be obtained from this supply. Notice that C2 through C7 must be ..
One-farad capacitors require some care. It`s a common knowledge that they must be pre-charged with a current-limiting resistor before plugging in. It is less common knowledge that those fifty-dollar `smart cap controllers` are in fact very simple devices,....
This circuit when used with a 555 timer will cause light emitting diodes to turn on and off more slowly. This will make the LEDs appear similar to incandescent lamps...
The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These IC`s are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but....
This Adjustable Strobe Light is the bigger brother of the plain old strobe light. This one uses a much more powerful "horse shoe" Xenon tube which produces more light. You can also control the flash rate up to about 20Hz. Do not look directly at the flash....
This relatively simple mixer was designed for three dynamic microphones, but can be re-designed for more or less. Level and tone controls are available to tailor the sound to your needs...
Only one out of 9,999 possible codes has the power to unlock this simple, yet effective, electronic lock. A combination lock is not just a perfect system to protect your belongings, it is also a valid system to let everyone to know that you are vigilant: an....
This design is based on one published by Milan Lulic in the German magazine elektroModell. Mr. Lulic`s design is for surface mount technology (SMT) construction, whereas mine uses standard off-the-shelf components, and is therefore better suited to....
This amplifier functions over a wide range of gains, typically 1-10. It combines the LT1010 and a fast discrete stage with an LT1008 based de stabilizing loop. Q1 and Q2 form a differential stage which single-ends into the LT1010. The circuit delivers 1 V....
By utilizing both halves of a dual timer it is possible to obtain sequential timing. By connecting the output of the first half to the input of the second half via a 01 µF coupling capacitor sequential timing may be obtained. Delay ti is determined by the....
The amplifier is capable of delivering around 1.5W into 8 ohm headphones, and 2.2W into 32 ohms - this is vastly more than will ever be needed in practice. The use of a 120 Ohm output resistor is recommended, as this is supposed to be the standard source....
Vinyl equalisation (EQ) has been with us in a stable and predictable form for quite a long time, but for those who are interested in the old 78 rpm records there are a great many problems to overcome. One of these is obtaining a turntable that runs at 78....
Before World War II the FM radio band was just below 50 Mc. Read all about it. If you have such a radio, you might want to build this converter. It will let your old set receive the modern FM band (88 to 108 Mc.). This design is based on an article I....
The fixed voltage power supply is useful in applications where an adjustable output is not required. This supply is simple, but very flexable as the voltage it outputs is dependant only on the regulator and transformer you choose. The maximum output current....
This circuit will emit an intermittent beep (or will flash a LED) when the water contained into a recipient has reached the desired level. It should be mounted on top of the recipient (e.g. a plastic tank) by means of two crocodile clips, acting also as....
Using two gates from a CMOS 4011 NAND chip, a simple aquarewave oscillator can br made. Alternatively a CMOS 4001 chip can also be used, or a TTL equivalent. In this circuit the mark space ratio can also be independantly controlled by varying the value of....
This circuit was used to trip a camera shutter. Grounding pin 2 of U1 makes pin 4 of U1 go high. This triggers both tim..
A simple boost circuit that gives 30 volts pk/pk output using a 9 volt battery. The addition of a Ge diode bridge makes a surprisingly good octave box...
This revision reduced the signal level and treble response in the preamp for a smoother sound in both cathode and fixed bias modes. The power supply was also revised for lower B+ voltages to the EL84 plates. "This amp was built on the chassis of an....
Room temperature plays a vital role in determining human thermal comfort. This digital thermometer is designed to measure room temperature and display it on a LCD screen in both Celsius and Fahrenheit scales. A PIC16F688 microchip is used as the main....
Power is applied to the circuit with the initiate switch open. The 25-JtF capacitor charges through the A14, or equivalent, diode and 2.2-KO resistor to full supply voltage. When the initiate switch is closed, the low side of the capacitor is suddenly....
This project is not to introduce Tic Tac Toe. Everyone knows this game. It`s to introduce two features. Bi-coloured LEDs, microcontrollers and the skill of writing an ALGORITHM. You can use the project to learn the skills of creating the Tic Tac Toe....
This system contains an IR transmitter, an IR receiver/RF transmitter, and an RF receiver/alert beeper. Two IR ..
At half brightness, the lamp current is pulsed on and off (Fig. 50-12b) by the voltage developed across the resistor and capacitor at the current-sense output. Lamp current is sensed by the current-sense output. A simple pulse-width modulation....
The circuit comprises two sections: charger power supply and LED driver.The charger power supply section is built around 3-terminal adjustable regulator (IC1) LM317, while the LED driver section is built around transistor BD140(T2). In the charger power....
This switch reacts to the touch of a finger to turn lights and/or appliances on or off. The device uses the human body as an..
The circuit accepts two positive-voltage inputs VN and Vv and provides a TTL-compatible output pulse train whose repetition mte is proportional to the ratio VN/ V0. Full-scale output frequency is about 100 Hz, and linearity error is below 0.5 percent. The....
This circuit turns a sine wave into a square wave. It is comprised of a single 2-input NAND Schmitt trigger that`s configured as an inverter with a trigger level adjustment at its input. As the input voltage rises above the gate`s trigger point,..
This jam circuit can be used in quiz contests wherein any par- ticipant who presses his button (switch) before the other contestants, gets the first chance to answer a question. The circuit given here permits up to eight contestants with each one allotted a....
Here"s an interesting mixer circuit. With it you can effectively combine signals from audio to high-fre-quency RF. Als..
The circuit spectator interference enables implantation mono sound at any point between stereo speakers. When P1 is in the middle of his journey, there is strengthening or weakening of the mark the entrance to the exit in any of the two channels. When the....
Loop Antennas are considered to be "samall" when their diameter drops below about 1/10 of the wavelength they are intended to be used at. In this case, I use the term "Tiny" because the antenna's diameter is about 1/30,000 the wavelength, and at 5.5 cm in....
This is a special low voltage version of my audio preamp. T1`s emitter voltage is biased close to half supply voltage (1.5V) to allow for maximum output voltage swing. Both transistors are direct coupled and have closed loop feedback to aid temperature....
I have no idea whether the RCA 40468A FET is still available or not. It came in a 4 pin metal can - with the 4th pin connected to the substrate. I have successfully substituted other N-channel devices, such as the HEP-802 - which comes in a plastic TO-92....
In the circuit shown below, if the voltage at the output terminals rises above 6.2V, zener conducts charging capacitor C4. This voltage will fire the silicon-controlled rectifier (SCR), which quickly shorts-or puts a ?crowbar? ? across the supply rails....
Many countries have 115 volts mains supplies. This can be a problem if your electric shaver is designed for 220/240 volts only. This simple rectifier voltage doubler enables motor driven 240 volt shavers to be operated at full speed from a 115 volt supply.....
The circuit, is based on a commercial temperature sensor (TS6178) and an MC3334P ignition chip, When the radiator temperature increases, the sensor pulls the base of Q2 low via Ql, which is wired as a diode. Q2`s collector thus goes high and triggers IC1,..
I keep all rights to those circuits myself. You may freely build those circuits to yourself and your friends, but commercial use of those circuits is not allowed. NOTE: Those circuits are old designs from time when I was not so good in electronics than I am....
The Atmel AVR series are very good microcontrollers with quite a rich instruction set, rich enough that lots of folks have good compilers for them so we don`t have to learn their assembler. A very rich compiler available is the BASCOM/AVR compiler from MCS....
Very little extra circuitry is needed to do both forword and backword walking sequences along with a few other tricks. The PIC16F818 has a lot of features that work well in this situation. As you can see from the Schematic and Source Listing, position....
Transmitter operation. Operating power for the transmitter circuit is derived directly from the ac line. The dc power to operate the circuit is generated in two stages, one for an RF power-am-plifier stage, and the second for the remainder of the circuit.....
One small spot of rain on the sense pad of this bleeper will start this audio warning. It can also be operated by rising water. The circuit has two transistors, with feedback via capacitor Cl, but Trl cannot operate as long as the moisture sense pad is dry. ..
For normal use it`s necessary to connect the battery, when the jumper is connected. Please take care, that the transmitter is on and the throttle is set to "power off"...
SPICE is the most commonly used analog circuit simulator today and is enormously important for the electronics industry. SPICE is a general purpose analog simulator which contains models for most circuit elements and can handle complex nonlinear circuits.....
The AY-3-8910/8912 is a register oriented Programmable Sound Generator (PSG). Communication between the processor and the PSG is based on the concept of memory-mapped I/O. Control commands are issued to the PSG by writing to 16 memory-mapped registers. Each....
This is simple almost beyond belief for distortion devices. Two transistors, four resistors, three capacitors, and two controls make all that tone. The first transistor is set up with the simplest of arrangements - input through a DC blocking capacitor....
