New Circuits Page 233
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This is the circuit of a 500 watt linear amplifier, based upon a design by Frits Geerligs, PA0FRI, who has his own homepage at http://home.planet.nl/~fhvgeerligs. The circuit uses four PL519 TV line output valves in a very simple circuit that will deliver....
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To safeguard portable, emergency power repeaters from reverse or excessive voltage, Dl prevents incorrect polarity damage, and zener voltage determines the maximum voltage that will reach the rest of the circuitry..
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The LCD display is represented by the connector X1. It has a HD44780 compatible LCD controller and I'm using the 4-bit interface to send data to the LCD controller. The LED's are multiplexed. I've seen the circuit somewhere in the web. It is possible to....
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The simple circuit in Figure 1a can sense both low and high current levels without low sensitivities or loss of accuracy either at the low or the high end of the scale. The circuit is useful for discerning either low or high currents in noisy environments...
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The circuit tests whether or not a diode is open, shorted, or functioning correctly. If lamp A lights, the diode under test is functional. When lamp B is lit, the diode is good but connected backwards..
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The potentiometer portion of a mixed-signal, digitally programmable potentiometer adds variability to an analog circuit, and its digital controls provide programmability. You can use a digital potentiometer in two ways in an analog circuit. You can use it as....
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For a dark photocell, high resistance, the vohage across the diac rises rapidly with the line voltage due to the current through C 1, triggering the diac early in the cycle. ..
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The schmitt trigger circuit is built around a single LM741 op-amp, its output buffered by a transistor, which in turn energizes a relay. The relay may be replaced by a red LED if desired. The LM741 may be replaced by a LF411 or other JFET input op-amp with....
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This design idea describes a simple circuit to generate a programmable negative control voltage. It takes the output of a single supply digital-to-analog converter (DAC) and produces a variable negative voltage. The DAC output from 0V to +2.5V is converted....
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The following design is capable of overlaying the time and date onto any existing PAL (or optionally NTSC) composite video signal. It is housed in a very neat and compact standard moulded casing and has standard 75ohm RCA video inputs and outputs. A single....
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This train detector makes use of hand held laser pointer devices that are widely available to detect trains over long distances...
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Figure 1 shows how to position a mechanical device into four discrete positions but with only two free outputs and one free input from the control system. The position depends on a set of cams and four corresponding limit switches. The 24V-dc motor comes....
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This small FM transmitter includes a limiter, a microphone amplifier and a PLL digital tuning. All the parts are placed on one circuit board. The RF power is switchable between 1 W (HI) and 0,2 W (LO). Technical specifications: Supply voltage: 12 V from....
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This circuits consist of two parts, the first part will transmit a signal, and the second part will detect that signal and trigger a relay.To adjust the circuit, hold down S1 while pointing LED1 at the receiver. Adjust R6 until you hear the relay click. You....
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The way that this circuit works is as follows. The AC line voltage is rectified by D1 and D2 which connects to a voltage doubler circuit made up of the two 22uf capacitors. The Flash Freq. Pot and the 10uf capacitor charge up which triggers the Diac and....
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Flashing occurs each time the capacitor discharges through the tumed-on SCR. When the discharge current falls below the SCR holding current, the SCR turns off, and the capacitor begins charging for another cycle. ..
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Integrated-circuit Ul—an LF351 or 741 op amp—is used as a comparator to control the light. Resistors R2 and R3 provide a reference voltage of about 2.5 volts at pin 3 of Ul. When daylight falls on light-dependent resistor LDR1, its resistance is low:....
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This pseudorandom sequencer drives a solid-state relay. If you power a low-wattage lamp from the relay, the lamp will appear to flicker like a candle"s flame in the wind; using higher-wattage lamps allows you to simulate the blaze of a fireplace or....
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If 12V relays are used, you can replace the 180R resistors R7,R9,R14,R16,R20,R22,R26 and R28 with a wire link (the resistors are only there to limit current if you use 5V relays, of which I had a load in my parts bin). If the system doesn't reset cleanly on....
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This simple amplifier is ideal for adding a headphone jack to equipment that lacks this feature. The Headphone Buffer circuit board is small enough (1.2" X 1.4") to squeeze into even the smallest spaces and power requirements are so low that existing....
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Input Amplifier Module: a low noise circuit equipped with a variable voltage-gain (10 - 100) pre-set, primarily intended as high quality microphone input, also suitable for low-level line input. High-quality modular design.
9V Battery powered - Very low....
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The LTC1050 is confi gured as unity gain 2nd order low-pass fi lter which center frequency is (1.2πR´C´) = 1.72 • fCUT-OFF = 17.2Hz and Q = 0.5. Figure 2 shows the amplitude response of the fi lter, and Figure 3 shows a well behaved transient response for....
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Ham Radio (amateur radio) is a popular hobby amongst electronics enthusiasts all over the world. Basically the hobby involves a person in making his own gear consisting of a receiver and transmitter or a transceiver (a receiver and a transmitter in one unit)....
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This circuit generates a low power test signal and should not be used as a transmitter. Make sure you are within the law in the locality in which you operate this. As this was built from parts laying on the bench, it isn't optimized, but it does demonstrate....
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The adapter allows four inputs to be displayed simultaoeously on a single trace scope. For low-frequency signals, less than 500Hz, the adapter is used in the chop mode at a frequency of 50 kHz. The clock can be run faster, but switching glitches and the....
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Momentary output : One of the relays RE1...RE4 is ON as long as CH1---CH4 is pressed from transmitter. Latch output: when one of channels CH1...CH4 is pressed from transmitter RE1...RE4 are ON as long as other CH is pressed from transmitter. Valid....
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The cost-effective design in Figure 1 provides control for CMOS switches without the need for an external power supply. Analog switches such as those in the MAX4663 are ideal for use in low-distortion applications. They are preferable to electromechanical....
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This transmitter was designed from the ground up to provide very high sound quality, coupled with excellent frequency stability, reliability, etc. It can be used as a standalone transmitter to serve a medium-sized town, or as an exciter to drive a....
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The inductor is made by winding 8 turns of #24 insulated solid copper wire on a 5 mm screwdriver. I used a conductor from a piece of category 5 quad twisted pair, left over from wiring the house with Ethernet and this seems to work well and to be easy to....
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This circuit of measurement of level uses the UAA180 of SIEMENS and a circuit of rectification of precision, round the IC2B. The calibration has become in steps 3db from the one Led in the other, ensuring, a very good rate of precision, in the measurement of....
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Two pairs of MOSFETs form a bridge that alternately switches current in opposite directions. Two parallel-resonant LC circuits complete the converter. The Ll/C1 combination is resonant at the fundamental frequency; the L2/C2 combination is resonant at the....
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Figure 1 shows a simplified schematic of a typical low-voltage halogen-lamp transformer without the protection circuits and EMI filter. Q1 and Q2 with C2 and C3 comprise a classic, half-bridge topology that works in self-oscillating mode. The circuit....
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This is an IR transmitting circuit which can be used in many projects (I designed this to try to make my 3D glasses wireless). This IR transmitter sends 40 kHz (frequency can be adjusted using R2) carrier under computer control (computer can turn the IR....
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The modular multiplexers described in this application
note, take these, as well as other points, into consideration
and provide an optimal solution for the video design engineer.
The 16x1 circuits are realised using four Gennum GX434 or
GX214, 4x1....
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The most elementary application is a half-wave control circuit. The thyristor is acting both as a power control device and as a rectifier, providing variable power to the load !luring the positive half cycle and no power to the load during the negative....
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This circuit combines a 555 timer with a 2N2222 transistor and an external potentiometer. The pot adjusts the output voltage to the desired value. To regulate the output voltage, the 2N2222 varies the control voltage of the 555 IC, increasing or decreasing....
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This circuit is designed to trigger on a 1 khz tone. to change this frequency - refer to the table below, then change the resistor and capacitor values accordingly...
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The Atmel Flash devices are ideal for developing, since they can be reprogrammed easy and fast. If you need more code space for your application, particularly for developing 89Cxx projects with C language. Atmel offers a broad range of microcontrollers based....
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This circuit dials a stored DTMF tone sequence from EPROM when a control line is taken to 0 V. ICl is a Schmitt trigger oscillator, running at around 2 Hz. It clocks a 4024 binary counter. The counter`s outputs connect to the address leads of the EPROM. A....
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This page describes how to build an adaptor for the Dreamcast serial port that will allow you to connect it to any computer using a standard 9-pin DSUB connector. The main component is a MAX voltage converter, since the Dreamcast serial port uses CMOS (3.3V)....
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If the amp is built on bipolar transistors, and the preamp/crossover on FETs, then they were designed by different guys, right? Not this amp. Here, a strong, experienced designer`s hand is evident from schematic to parts layout, PCB routing and general....
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Timer Ul operates as a free-running oscillator at 60 Hz, providing trigger pulses to timer U2 which operates in the monostable mode. Resistor Rl is fixed and capacitor Cx is the capacitor being measured. While the output of U2 is 60 Hz, the duty cycle....
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This circuit allows a 12v relay to operate on a 6v or 9v supply. Most 12v relays need about 12v to "pull-in" but will "hold" on about 6v. The 220u charges via the 2k2 and bottom diode. When an input above 1.5v is applied to the input of the circuit, both....
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This project describes a little QRP transceiver full legal power” (5 W at 12 V) for the 40
meters band. The RIG may be built in a gradual manner, in fact it is divided in two main modules, or
you may also complete only the RX module. The RX section is....
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The operation of the circuit is fairly simple. Three AND logic gates of a 4081 CMOS IC are employed, with gates IC1a to IC1c being configured as a standard cascaded latch circuit. S1 to S3 serve as reset switches. The output at pin 10 will only switch to....
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In this project AT89S52 microcontroller is used for interfacing to various hardware peripherals. The current design is an embedded application, which will continuously monitor a moving Vehicle and report the status of the Vehicle on demand. For doing so an....
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Adding a simple clamping circuit to a Harris 2620 high-speed op amp produces a glitch-free amplifier/ clipper. The op a..
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The combination of Ql, Q2 and Ul form a hysteresis oscillator to stabilize lamp illumination. In operation, full wave bridge D3 operates directly from the ac line to supply unregulated dc to the lamp and also to the 10 V zener that provides power to the quad....
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This riaa Pre-Amp is the perfect solution to getting a signal off of your old turntable and into your mixing board. Whether you want to grab a couple of loops from a 70s LP record or just archive your record collection you need an riaa compensated pre-amp to....
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In this small switching power supply, a Schmitt trigger oscillator is used to drive a switching transistor that supplies current to a small inductor. Energy is stored in the inductor while the transistor is on, and released into the load circuit when the....
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This simple circuit gives a positive and negative supply from a single transformer winding and one full-wave bridge. Two zener diodes in series provide the voltage division and their centerpoint is grounded..
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For positive protection of electrical or electronic equipment, use this against excessive supply voltage. Due to improper switching, wiring, short circuits, or failure of regulators, an electronic crowbar circuit can quickly place a short circuit across the....
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In the wiper-delay schematic shown, with the ignition on, Dl maintains regulated +12 Vdc. When SI closes..
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This simple circuit generates a dual-speed clock for personal computers. The circuit synchronizes your asynchronous switch inputs with the master clock to provide glitch-free transitions from one clock speed to the other. The dual-speed clock allows some....
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The HA2541 is well-suited for use as the heart of an oscillator. In spite of the rudimentary diode limiting that is ..
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With a constant current excitation, the voltage dropped across an inductance in-(in creases with frequency. Thus, an active device whose output increases with frequency can be characterized as an inductance. The circuit yields such a response with the....
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This is an easy to build stepper motor driver that will allow you to precisely control a unipolar stepper motor through your computer`s parallel port. With a stepper motor you can build a lot of interesting gadgets such as robots, elevator, PCB drilling....
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Peak reading meters, popular in Europe for years, are just now coming into greater favor in America, and for good reason. The main purpose for having a VU meter is obviously to monitor signal levels going to a tape recorder, reverb unit, or some other....
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One yet circuit with the known LM3915. It does not differ in a lot of points from other applications with same IC. The circuit accosted in those who they want a Vumeter that will be connected in the exit of power amplifier. It can be adapted his sensitivity....
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This single-stage amplifier (using a 2N2222 or 2N3904 general-purpose transistor) is useful for interfacing test in..
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The voltage-to-current converter in Figure 1 can both source and sink current. The circuit is more flexible than some traditional current references that require different topologies for current sourcing and sinking. Also, you can easily adjust the value of....
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For the primary multiplier, the "folder", connect the input to the triangle wave output of a VCO. Connect a LFO, envelope generator or even a DC voltage to the folds input. The result will be a harmonically rich signal at the "F out" output. A second input....
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If the battery voltage exceeds about 11 V, current flows through R1, D1, and R2. The voltage produced as a result of current flow through R2 is sufficient to bias transistor Q1 into conduction. That places the collector voltage of Q1 virtually at....
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Comprising two low-power, CMOS chips, thepulse generator produces a precise pulse width in the 50 to 500 ns range. ICl is a dual monostable multivibrator (one shot) in which each positive trigger pulse initiates simultaneous positive output pulses at pins....
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This article discusses several opamp-based headphone amplifier circuits, including suggestions for selecting opamps, input coupling and filtering, high current output stages and power supply options. There are no recommendations for specific opamp brands or....
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To design a Tube Headphone Amplifier we need a triode with uncommon characteristics: enough voltage gain, low internal resistance and good anodic current. My first test was done with the E182CC (figure 1), but there is the limitation on the usable impedance....
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An NEC602 is used as a mixer with a zero IF frequency output, U2 acts as an audio amplifier. This receiver is primarily for SSB and CW signals. Tl and T2 are 10.7-MHz IF coils used in AM/FM transistorized radios, etc...
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This linear amplifier delivers 10-W PEP output; with 1.25-W drive on 10 m. Tl, T2, and T3 are 10 turns of bifilar windings on an FT-50-43 toroidal core. The transformers are broadband. Filters for other bands, if desired, are shown. Note: use #26 wire for....
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Here is some experimental hardware and software to transmit and receive AX.25 packets.
It is essentially a PIC-E clone designed around a Atmel AT90S2313 with a few extra bells and whistles.
I had picked up a couple of MXCOM MX-614s at the TAPR display (I....
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Tests 1.5 to 15 Volt cells. This circuit runs a fast battery test without the need of power supply or expensive moving-coil voltmeters. It features two ranges: when SW1 is set as shown in the circuit diagram, the device can test 3V to 15V batteries. When SW1....
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This is a low power voltmeter circuit that can be used with alternative energy systems that run on 12 and 24 volt batteries. The voltmeter is an expanded scale type that indicates small voltage steps over the 10 to 16 volt range for 12 volt batteries and....
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Sometimes when experimenting with different soundcards and MIDI interfaces it is useful to see if there is some data going in MIDI interface. This can be easily tested with this adapter, which converts the midi signals to visible light pulses. Just the....
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The rotary switch is available for $5.00USD as of 2003 from DigiKey under part number EG1951-ND or EG1952-ND. It is a real pain to operate this circuit without a proper switch. You can put multiple 4017 ring counters in series to reduce the duty cycle in....
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This article explains the specifications and characteristics of crystals and crystal oscillators, and aids in specifying crystals and working with crystal vendors. The article covers the significant performance characteristics of crystals, which include....
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Driving the highway with your high-beam headlights can really increase your visibility, but can be a blinding hazard for other drivers. This simple circuit can be wired into your headlight switch to provide automatic switching between high and low beam....
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The PMR VHF transceiver Motorola Radius M110 (in further text referred as M110) was manufactured by Motorola GmbH therefore being an European radio. Since many professional radio service users has replaced this transceiver with newer gear, a considerable....
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The radio beacon band extends from 280 to 516 kHz. Each beacon has its own characteristic AM"-modulated morse-coded ..
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This circuit can generate a European police-car siren, bird noises, spaceship sounds, etc. In addition, it can be put to use as a doorbell, an alarm, etc. The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output....
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A 4017 decade counter/divider driven from a low-frequency oscillator (Ul-a and Ul-b) is used to drive transistor switches to sequence the windings, as is needed. MOT1 is a 12-V stepper motor. R9 and RIO are selected for the motor`s current rating. A 3.3-Hz....
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After the SCR turns on, CI charges up to almost the full supply voltage via R3 and the anode of the SCR. Whe..
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This preamp is very simple, and will work under tough conditions. The input impedance is pretty high, so it won`t load down electric guitars. It will also amplify microphones. When I have a moment, I`ll make some additions that will optimize it for....
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This almost trivial circuit may be used to charge a pair of AA or AAA sized rechargeable battery cells from sunlight. The circuit has been used to keep a Palm Pilot and walkman radio running perpetually. This is an unregulated charger, proper charging is....
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This circuit will not work unless the battery to be charged is connected with proper polarity. The battery voltage controls the charger and when the battery is fully charged, the charger will not supply current to the battery. The battery charging the....
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This supply is powered by a transformer operating from 120 Vac on the primary and providing approximately 20 Vac on the primary, and providing approximately 20 Vac on the secondary. Four 10-A diodes with a 100 PIV rating are used in a full-wave bridge....
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To prevent loss of data when a CMOS RAM is switched from normal operation (Vcc = 5 volts) to stand-by mode (Vcc = VBAT) it must be ensured that the CS pin goes near the Vcc rail at all times. Ac coupling to the chip select is made through capacitor C,....
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For systems with only one power supply, two op amps act as instrumentation and buffer amps. The OPA111..
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These pages describe my project to build simpler and less expensive amateur seismometers by using microprocessors and other new chips, such as switched capacitor filters. I have tried to provide links to much of the excellent information that is already on....
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This circuit detects the 20 Hz, "" 86-V rms ring signal on telephone lines and initiates action in an electrically isolated circuit. Typical applications would include automatic answering equipment, and interconnect/ interface and key systems. The circuits....
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The injector is a CMOS oscillator with period approximately equal to 1 x Cl x R2 seconds. The values are given for 1 kHz operation. Resistors R3 and R4 divide theoutput to 1 V; Whereas the oscillator employs the gates in their digital mode, the tracer used....
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This converter can accommodate wide inputvoltage swings, such as the 8 to 15-V swing typical of a 12-V sealed lead/acid battery. The low battery output indicates when input voltage drops below 8V. ..
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This circuit outputs a TTL-compatible - pulse whenever the signal falls within the limits set by potentiometers ..
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No description available...
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The name of our game, LED Zeppelin, is a play on words. It comes not from the pop group of the same name but from Graf Von Zeppelin, a German who invented the first rigid air ship in 1900.
The association fits perfectly. The game consists of six LEDs and an....
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The transmitter for the wireless headphones is built around a CD4046 CMOS phase-locked loop, coupled with a driver transistor, and a pair of infrared LEDs. Although the CD4046 is comprised of two phase comparators, a voltage-controlled oscillator (or VCO),..
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Capacitor C5 and potentiometer R12 determine the frequency of the output signal at pin 3 of IC1, the 555 oscillator. The output signal is differentiated by C3 and C4 before it"s input to the base of power transistors Q1 and Q2 via diodes D1 and D2,....
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The alarm circuit has a single 555 oscillator/timer (Ul) performing double duty; serving both in the alarm-trigger circuit arid the entry- delay circuit. In this application, the trigger input of IJ1 at pin 2 is held high via Rl. A normally-closed sensor....
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This system uses an MM5369 IC to derive a 60-Hz signal from a TV burst crystal (3579 MHz). F8 and V9 producc a 10-Hz and 1-Hz signal from this 60-Hz signal...
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Using digital techniques, this circuit accomplishes the frequency-inversion algorithm via digitization of the audio, inversion of the sign of every alternate sample, and D/A conversion of the resultant data. The result is an inverted frequency spectrum...
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IC1 is a switching regulator that generates a 45-kHz signal that drives the gate of MOSFET Ql. Dl, D2, an..
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The ICL8212 is connected as a programmable zener diode. Zener voltages from 2 V up to 30 V can be programmed by suitably..
This is the circuit of a 500 watt linear amplifier, based upon a design by Frits Geerligs, PA0FRI, who has his own homepage at http://home.planet.nl/~fhvgeerligs. The circuit uses four PL519 TV line output valves in a very simple circuit that will deliver....
To safeguard portable, emergency power repeaters from reverse or excessive voltage, Dl prevents incorrect polarity damage, and zener voltage determines the maximum voltage that will reach the rest of the circuitry..
The LCD display is represented by the connector X1. It has a HD44780 compatible LCD controller and I'm using the 4-bit interface to send data to the LCD controller. The LED's are multiplexed. I've seen the circuit somewhere in the web. It is possible to....
The simple circuit in Figure 1a can sense both low and high current levels without low sensitivities or loss of accuracy either at the low or the high end of the scale. The circuit is useful for discerning either low or high currents in noisy environments...
The circuit tests whether or not a diode is open, shorted, or functioning correctly. If lamp A lights, the diode under test is functional. When lamp B is lit, the diode is good but connected backwards..
For a dark photocell, high resistance, the vohage across the diac rises rapidly with the line voltage due to the current through C 1, triggering the diac early in the cycle. ..
The schmitt trigger circuit is built around a single LM741 op-amp, its output buffered by a transistor, which in turn energizes a relay. The relay may be replaced by a red LED if desired. The LM741 may be replaced by a LF411 or other JFET input op-amp with....
The following design is capable of overlaying the time and date onto any existing PAL (or optionally NTSC) composite video signal. It is housed in a very neat and compact standard moulded casing and has standard 75ohm RCA video inputs and outputs. A single....
This train detector makes use of hand held laser pointer devices that are widely available to detect trains over long distances...
This small FM transmitter includes a limiter, a microphone amplifier and a PLL digital tuning. All the parts are placed on one circuit board. The RF power is switchable between 1 W (HI) and 0,2 W (LO). Technical specifications: Supply voltage: 12 V from....
This circuits consist of two parts, the first part will transmit a signal, and the second part will detect that signal and trigger a relay.To adjust the circuit, hold down S1 while pointing LED1 at the receiver. Adjust R6 until you hear the relay click. You....
The way that this circuit works is as follows. The AC line voltage is rectified by D1 and D2 which connects to a voltage doubler circuit made up of the two 22uf capacitors. The Flash Freq. Pot and the 10uf capacitor charge up which triggers the Diac and....
Flashing occurs each time the capacitor discharges through the tumed-on SCR. When the discharge current falls below the SCR holding current, the SCR turns off, and the capacitor begins charging for another cycle. ..
Integrated-circuit Ul—an LF351 or 741 op amp—is used as a comparator to control the light. Resistors R2 and R3 provide a reference voltage of about 2.5 volts at pin 3 of Ul. When daylight falls on light-dependent resistor LDR1, its resistance is low:....
This pseudorandom sequencer drives a solid-state relay. If you power a low-wattage lamp from the relay, the lamp will appear to flicker like a candle"s flame in the wind; using higher-wattage lamps allows you to simulate the blaze of a fireplace or....
If 12V relays are used, you can replace the 180R resistors R7,R9,R14,R16,R20,R22,R26 and R28 with a wire link (the resistors are only there to limit current if you use 5V relays, of which I had a load in my parts bin). If the system doesn't reset cleanly on....
This simple amplifier is ideal for adding a headphone jack to equipment that lacks this feature. The Headphone Buffer circuit board is small enough (1.2" X 1.4") to squeeze into even the smallest spaces and power requirements are so low that existing....
Input Amplifier Module: a low noise circuit equipped with a variable voltage-gain (10 - 100) pre-set, primarily intended as high quality microphone input, also suitable for low-level line input. High-quality modular design. 9V Battery powered - Very low....
The LTC1050 is confi gured as unity gain 2nd order low-pass fi lter which center frequency is (1.2πR´C´) = 1.72 • fCUT-OFF = 17.2Hz and Q = 0.5. Figure 2 shows the amplitude response of the fi lter, and Figure 3 shows a well behaved transient response for....
Ham Radio (amateur radio) is a popular hobby amongst electronics enthusiasts all over the world. Basically the hobby involves a person in making his own gear consisting of a receiver and transmitter or a transceiver (a receiver and a transmitter in one unit)....
This circuit generates a low power test signal and should not be used as a transmitter. Make sure you are within the law in the locality in which you operate this. As this was built from parts laying on the bench, it isn't optimized, but it does demonstrate....
The adapter allows four inputs to be displayed simultaoeously on a single trace scope. For low-frequency signals, less than 500Hz, the adapter is used in the chop mode at a frequency of 50 kHz. The clock can be run faster, but switching glitches and the....
Momentary output : One of the relays RE1...RE4 is ON as long as CH1---CH4 is pressed from transmitter. Latch output: when one of channels CH1...CH4 is pressed from transmitter RE1...RE4 are ON as long as other CH is pressed from transmitter. Valid....
This transmitter was designed from the ground up to provide very high sound quality, coupled with excellent frequency stability, reliability, etc. It can be used as a standalone transmitter to serve a medium-sized town, or as an exciter to drive a....
The inductor is made by winding 8 turns of #24 insulated solid copper wire on a 5 mm screwdriver. I used a conductor from a piece of category 5 quad twisted pair, left over from wiring the house with Ethernet and this seems to work well and to be easy to....
This circuit of measurement of level uses the UAA180 of SIEMENS and a circuit of rectification of precision, round the IC2B. The calibration has become in steps 3db from the one Led in the other, ensuring, a very good rate of precision, in the measurement of....
Two pairs of MOSFETs form a bridge that alternately switches current in opposite directions. Two parallel-resonant LC circuits complete the converter. The Ll/C1 combination is resonant at the fundamental frequency; the L2/C2 combination is resonant at the....
This is an IR transmitting circuit which can be used in many projects (I designed this to try to make my 3D glasses wireless). This IR transmitter sends 40 kHz (frequency can be adjusted using R2) carrier under computer control (computer can turn the IR....
The most elementary application is a half-wave control circuit. The thyristor is acting both as a power control device and as a rectifier, providing variable power to the load !luring the positive half cycle and no power to the load during the negative....
This circuit combines a 555 timer with a 2N2222 transistor and an external potentiometer. The pot adjusts the output voltage to the desired value. To regulate the output voltage, the 2N2222 varies the control voltage of the 555 IC, increasing or decreasing....
This circuit is designed to trigger on a 1 khz tone. to change this frequency - refer to the table below, then change the resistor and capacitor values accordingly...
The Atmel Flash devices are ideal for developing, since they can be reprogrammed easy and fast. If you need more code space for your application, particularly for developing 89Cxx projects with C language. Atmel offers a broad range of microcontrollers based....
This circuit dials a stored DTMF tone sequence from EPROM when a control line is taken to 0 V. ICl is a Schmitt trigger oscillator, running at around 2 Hz. It clocks a 4024 binary counter. The counter`s outputs connect to the address leads of the EPROM. A....
This page describes how to build an adaptor for the Dreamcast serial port that will allow you to connect it to any computer using a standard 9-pin DSUB connector. The main component is a MAX voltage converter, since the Dreamcast serial port uses CMOS (3.3V)....
If the amp is built on bipolar transistors, and the preamp/crossover on FETs, then they were designed by different guys, right? Not this amp. Here, a strong, experienced designer`s hand is evident from schematic to parts layout, PCB routing and general....
Timer Ul operates as a free-running oscillator at 60 Hz, providing trigger pulses to timer U2 which operates in the monostable mode. Resistor Rl is fixed and capacitor Cx is the capacitor being measured. While the output of U2 is 60 Hz, the duty cycle....
This circuit allows a 12v relay to operate on a 6v or 9v supply. Most 12v relays need about 12v to "pull-in" but will "hold" on about 6v. The 220u charges via the 2k2 and bottom diode. When an input above 1.5v is applied to the input of the circuit, both....
This project describes a little QRP transceiver full legal power” (5 W at 12 V) for the 40 meters band. The RIG may be built in a gradual manner, in fact it is divided in two main modules, or you may also complete only the RX module. The RX section is....
The operation of the circuit is fairly simple. Three AND logic gates of a 4081 CMOS IC are employed, with gates IC1a to IC1c being configured as a standard cascaded latch circuit. S1 to S3 serve as reset switches. The output at pin 10 will only switch to....
In this project AT89S52 microcontroller is used for interfacing to various hardware peripherals. The current design is an embedded application, which will continuously monitor a moving Vehicle and report the status of the Vehicle on demand. For doing so an....
Adding a simple clamping circuit to a Harris 2620 high-speed op amp produces a glitch-free amplifier/ clipper. The op a..
The combination of Ql, Q2 and Ul form a hysteresis oscillator to stabilize lamp illumination. In operation, full wave bridge D3 operates directly from the ac line to supply unregulated dc to the lamp and also to the 10 V zener that provides power to the quad....
This riaa Pre-Amp is the perfect solution to getting a signal off of your old turntable and into your mixing board. Whether you want to grab a couple of loops from a 70s LP record or just archive your record collection you need an riaa compensated pre-amp to....
In this small switching power supply, a Schmitt trigger oscillator is used to drive a switching transistor that supplies current to a small inductor. Energy is stored in the inductor while the transistor is on, and released into the load circuit when the....
This simple circuit gives a positive and negative supply from a single transformer winding and one full-wave bridge. Two zener diodes in series provide the voltage division and their centerpoint is grounded..
For positive protection of electrical or electronic equipment, use this against excessive supply voltage. Due to improper switching, wiring, short circuits, or failure of regulators, an electronic crowbar circuit can quickly place a short circuit across the....
In the wiper-delay schematic shown, with the ignition on, Dl maintains regulated +12 Vdc. When SI closes..
This simple circuit generates a dual-speed clock for personal computers. The circuit synchronizes your asynchronous switch inputs with the master clock to provide glitch-free transitions from one clock speed to the other. The dual-speed clock allows some....
The HA2541 is well-suited for use as the heart of an oscillator. In spite of the rudimentary diode limiting that is ..
With a constant current excitation, the voltage dropped across an inductance in-(in creases with frequency. Thus, an active device whose output increases with frequency can be characterized as an inductance. The circuit yields such a response with the....
This is an easy to build stepper motor driver that will allow you to precisely control a unipolar stepper motor through your computer`s parallel port. With a stepper motor you can build a lot of interesting gadgets such as robots, elevator, PCB drilling....
Peak reading meters, popular in Europe for years, are just now coming into greater favor in America, and for good reason. The main purpose for having a VU meter is obviously to monitor signal levels going to a tape recorder, reverb unit, or some other....
One yet circuit with the known LM3915. It does not differ in a lot of points from other applications with same IC. The circuit accosted in those who they want a Vumeter that will be connected in the exit of power amplifier. It can be adapted his sensitivity....
This single-stage amplifier (using a 2N2222 or 2N3904 general-purpose transistor) is useful for interfacing test in..
If the battery voltage exceeds about 11 V, current flows through R1, D1, and R2. The voltage produced as a result of current flow through R2 is sufficient to bias transistor Q1 into conduction. That places the collector voltage of Q1 virtually at....
Comprising two low-power, CMOS chips, thepulse generator produces a precise pulse width in the 50 to 500 ns range. ICl is a dual monostable multivibrator (one shot) in which each positive trigger pulse initiates simultaneous positive output pulses at pins....
This article discusses several opamp-based headphone amplifier circuits, including suggestions for selecting opamps, input coupling and filtering, high current output stages and power supply options. There are no recommendations for specific opamp brands or....
To design a Tube Headphone Amplifier we need a triode with uncommon characteristics: enough voltage gain, low internal resistance and good anodic current. My first test was done with the E182CC (figure 1), but there is the limitation on the usable impedance....
An NEC602 is used as a mixer with a zero IF frequency output, U2 acts as an audio amplifier. This receiver is primarily for SSB and CW signals. Tl and T2 are 10.7-MHz IF coils used in AM/FM transistorized radios, etc...
This linear amplifier delivers 10-W PEP output; with 1.25-W drive on 10 m. Tl, T2, and T3 are 10 turns of bifilar windings on an FT-50-43 toroidal core. The transformers are broadband. Filters for other bands, if desired, are shown. Note: use #26 wire for....
Here is some experimental hardware and software to transmit and receive AX.25 packets. It is essentially a PIC-E clone designed around a Atmel AT90S2313 with a few extra bells and whistles. I had picked up a couple of MXCOM MX-614s at the TAPR display (I....
Tests 1.5 to 15 Volt cells. This circuit runs a fast battery test without the need of power supply or expensive moving-coil voltmeters. It features two ranges: when SW1 is set as shown in the circuit diagram, the device can test 3V to 15V batteries. When SW1....
This is a low power voltmeter circuit that can be used with alternative energy systems that run on 12 and 24 volt batteries. The voltmeter is an expanded scale type that indicates small voltage steps over the 10 to 16 volt range for 12 volt batteries and....
Sometimes when experimenting with different soundcards and MIDI interfaces it is useful to see if there is some data going in MIDI interface. This can be easily tested with this adapter, which converts the midi signals to visible light pulses. Just the....
The rotary switch is available for $5.00USD as of 2003 from DigiKey under part number EG1951-ND or EG1952-ND. It is a real pain to operate this circuit without a proper switch. You can put multiple 4017 ring counters in series to reduce the duty cycle in....
This article explains the specifications and characteristics of crystals and crystal oscillators, and aids in specifying crystals and working with crystal vendors. The article covers the significant performance characteristics of crystals, which include....
Driving the highway with your high-beam headlights can really increase your visibility, but can be a blinding hazard for other drivers. This simple circuit can be wired into your headlight switch to provide automatic switching between high and low beam....
The PMR VHF transceiver Motorola Radius M110 (in further text referred as M110) was manufactured by Motorola GmbH therefore being an European radio. Since many professional radio service users has replaced this transceiver with newer gear, a considerable....
The radio beacon band extends from 280 to 516 kHz. Each beacon has its own characteristic AM"-modulated morse-coded ..
This circuit can generate a European police-car siren, bird noises, spaceship sounds, etc. In addition, it can be put to use as a doorbell, an alarm, etc. The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output....
A 4017 decade counter/divider driven from a low-frequency oscillator (Ul-a and Ul-b) is used to drive transistor switches to sequence the windings, as is needed. MOT1 is a 12-V stepper motor. R9 and RIO are selected for the motor`s current rating. A 3.3-Hz....
After the SCR turns on, CI charges up to almost the full supply voltage via R3 and the anode of the SCR. Whe..
This preamp is very simple, and will work under tough conditions. The input impedance is pretty high, so it won`t load down electric guitars. It will also amplify microphones. When I have a moment, I`ll make some additions that will optimize it for....
This almost trivial circuit may be used to charge a pair of AA or AAA sized rechargeable battery cells from sunlight. The circuit has been used to keep a Palm Pilot and walkman radio running perpetually. This is an unregulated charger, proper charging is....
This circuit will not work unless the battery to be charged is connected with proper polarity. The battery voltage controls the charger and when the battery is fully charged, the charger will not supply current to the battery. The battery charging the....
This supply is powered by a transformer operating from 120 Vac on the primary and providing approximately 20 Vac on the primary, and providing approximately 20 Vac on the secondary. Four 10-A diodes with a 100 PIV rating are used in a full-wave bridge....
To prevent loss of data when a CMOS RAM is switched from normal operation (Vcc = 5 volts) to stand-by mode (Vcc = VBAT) it must be ensured that the CS pin goes near the Vcc rail at all times. Ac coupling to the chip select is made through capacitor C,....
For systems with only one power supply, two op amps act as instrumentation and buffer amps. The OPA111..
This circuit detects the 20 Hz, "" 86-V rms ring signal on telephone lines and initiates action in an electrically isolated circuit. Typical applications would include automatic answering equipment, and interconnect/ interface and key systems. The circuits....
The injector is a CMOS oscillator with period approximately equal to 1 x Cl x R2 seconds. The values are given for 1 kHz operation. Resistors R3 and R4 divide theoutput to 1 V; Whereas the oscillator employs the gates in their digital mode, the tracer used....
This converter can accommodate wide inputvoltage swings, such as the 8 to 15-V swing typical of a 12-V sealed lead/acid battery. The low battery output indicates when input voltage drops below 8V. ..
This circuit outputs a TTL-compatible - pulse whenever the signal falls within the limits set by potentiometers ..
The name of our game, LED Zeppelin, is a play on words. It comes not from the pop group of the same name but from Graf Von Zeppelin, a German who invented the first rigid air ship in 1900. The association fits perfectly. The game consists of six LEDs and an....
The transmitter for the wireless headphones is built around a CD4046 CMOS phase-locked loop, coupled with a driver transistor, and a pair of infrared LEDs. Although the CD4046 is comprised of two phase comparators, a voltage-controlled oscillator (or VCO),..
Capacitor C5 and potentiometer R12 determine the frequency of the output signal at pin 3 of IC1, the 555 oscillator. The output signal is differentiated by C3 and C4 before it"s input to the base of power transistors Q1 and Q2 via diodes D1 and D2,....
The alarm circuit has a single 555 oscillator/timer (Ul) performing double duty; serving both in the alarm-trigger circuit arid the entry- delay circuit. In this application, the trigger input of IJ1 at pin 2 is held high via Rl. A normally-closed sensor....
This system uses an MM5369 IC to derive a 60-Hz signal from a TV burst crystal (3579 MHz). F8 and V9 producc a 10-Hz and 1-Hz signal from this 60-Hz signal...
Using digital techniques, this circuit accomplishes the frequency-inversion algorithm via digitization of the audio, inversion of the sign of every alternate sample, and D/A conversion of the resultant data. The result is an inverted frequency spectrum...
IC1 is a switching regulator that generates a 45-kHz signal that drives the gate of MOSFET Ql. Dl, D2, an..
The ICL8212 is connected as a programmable zener diode. Zener voltages from 2 V up to 30 V can be programmed by suitably..
