New Circuits Page 240
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This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the....
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IC1 contains several oscillators and an amplifier. The low-frequency audio-signal oscillator is used to supply an input to the amplifier. That signal is the audio tone that is amplified, then supplied to the speaker by the amplifier. The high-frequency....
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The circuit is based on a simple inductor-capacitor filter circuit, and needs only a pot and a small light bulb to set and stabilise the oscillation. The frequency is fixed, and with a good inductor should be capable of very low distortion. This circuit is....
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If you are busy and cannot answer or do not wish to answer your phone, this circuit will give a busy signal without you ..
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This circuit keeps an automobile's headlights on temporarily. It also will turn the lights off, even if you forget to flip the light switch. The circuit's shut-off delay is actuated only after both the ignition and light switches have been on, and only if....
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Rectangular pulse generators, even at high frequencies, are easy to design. However, the design becomes more difficult if you need a signal that contains a precise number of periods with a sinusoidal shape. Although it is easy to produce a good sine wave,....
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The circuit provides three square wave outputs with 120° of phase difference between each other. Reference clock frequency is twice that of the required frequency. This can be obtained from a crystal oscillator with a chain of dividers or by using LM 555 in....
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This is a voltage controller oscillator that was designed as a wide range oscillator to generate clock pulses for a stepper motor drive system. It does however have some interesting features. The original application used a stepper motor for its ability to....
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This signal generator uses a three channel DAC to generate Composite video signal (CVBS) and S video signal (Y/C separated) at the same time, left one channel is not used in NTSC format. It is assigned for one of the color components of Y/CB/CR video format...
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These circuits could be used as the basis for Model Railroad DCC Boosters or PWM motor controllers. The first schematic is for a basic 3 Amp - DCC Booster using the LMD 18200 CMOS, H-Bridge.
Included in the design is a 5Volt regulator that supplies....
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A center-tapped 240-V transformer is used with two SCR devices to provide rectified ac (pulsating dc) to MOT1...
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This rf power switch operates at 1. 7 MHz with a 50-V source and load. Its on loss is 0.2 dB and its off isolation is 30 dB. It provides 40-W PEP, 45 VrEAK and 0.9 APEAK· The control input can come from CMOS, TTL, LS, etc., ..
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Here are some utility circuits for use with the Ramsey FM10a, and other small FM stereo transmitter kits. This information may be helpful for setting up a micro powered FM radio station. The FM10a and similar kits tend to put out a low quality, broad band....
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This is a sensitive, mini-powered FM transmitter consisting of an rf oscillator section interfaced with a high-sensitivity wide passband audio amplifier and capacitance microphone with built-in FET that modulates the base of the rf oscillator transistor.....
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This circuit was inspired by a friend who wanted a reberb
for his portable guitar amplifier. I originally tried using NE5532
low noise op-amps for the buffer stages but they were too noisy
for the low level circuits so I switched to discrete 2N3904....
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The circuit in Figure 1 provides a way to check a battery`s condition. Measuring a battery`s voltage is not the best way to check its condition; it`s better to measure the power that the battery delivers in a discharge process to evaluate the battery`s....
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On most FM tuners, the stereo indicator lights upon detection of the 19-kHz pilot tone. However, this doesn"t mean that the program is actually stereophonic, since the pilot tone is often transmitted with mono programs also. A similar situation exists on....
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Two NAND gates are used for the oscillator, and two as the control. If the two-tone speed needs to be altered, the 220 µ capacitors can be changed Oarger for slower operation). If the frequency of the oscillator is to be changed, the 0.2 and 0.1 /iF....
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In this configuration, the display reads hertz directly. With pin 11 of the ICM7027 A connected to V00, the gating time will be 0.1 second; this will display tens of hertz as the least significant digit. ..
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The circuit consists of ICM7208 seven-decade counter U1, ICM7207A oscillator controller U2, and CA3130 biFET op amp U3. IC U1 counts input signals, decodes them to 7-segment format, and outputs signals that are used to drive a 7-digit display. IC U2....
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The modulator and oscillator consist of two NPN transistors. The base of the modulator transistor is driven by a bidirectional current source with the voltage range for the high condition limited by a saturating PNP collector to the pin 4 Vreg voltage and....
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This is a Crystal Receiver using 741 IC chip. Frequency range is between 500-1600Khz...
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Reverse engineered circuit diagram of a popular retail doorknob alarm. It contains a small transmitter and the doorknob acts as an antenna so it will not work on a metal door. When a person comes close to the doorknob this loads down the oscillator and the....
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The variable voltage regulator lets you adjust the output voltage of a fixed de power supply between 1.2 and 37 V de, and will supply the output current in excess of 1.5 A. The circuit incorporates an LM117K three-terminal adjustable output positive....
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This circuit provides accurate full-wave rectification. The output impedance is low for both input polarities, and the errors are small at all signal levels. Note that the output will not sink heavy currents, except a small amount through the 10-K!J....
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Many beginners trying out their skill with QRP TX, for the first time have to overcome many problems before they are able to come on the air. On usual complaint is that, every thing is working fine but the signal is not going out. Here is a simple set up....
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This is an experimental work to monitor a spectrum pattern of radio band, and is a continuous project from Audio Spectrum Monitor. To analyze the spectrum of an input signal, I chose an Atmel`s AVR microcontroller used in Audio Spectrum Monitor to process....
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Sometimes caller might want to preserve his privacy so that his/her number is not send to the called person. Legistlation say that caller must have some way to disable sending of the called ID information when he/she wants to. This can be done by dialling s....
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The crystal used in the topology of Figure 1 can be either a fundamental AT-CUT or BT-CUT. A BT-CUT crystal has poor frequency stability over temperature compared to an AT-CUT. This topology uses a parallel crystal and not a series crystal...
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If you are not using the Aiptek camera then it will be up to YOU to determine how to hack your particular digital camera. The camera that was used in the project is the tiny Aiptek Mini PenCam 1.3. However, other cameras are possible candidates too since the....
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The 24 watt amp is easy to build, and very inexpensive. The circuit can be used as a booster in a car audio system, an amp for satellite speakers in a surround sound or home theater system, or as an amp for computer speakers. The circuit is quite compact and....
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The simplest of all motor controllers (besides a straight on/off switch) is the contactor controller. I designed this contactor controller for use in my electric scooter project. It is based around three 12V relays, two 12V batteries, two switches and of....
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Easy to build, this high voltage generator is capable of generating up to 50KV but the breakdown voltage of the coil limits the voltage to a value somewhat lower. T2 is the ignition coil of a car and also the 0.5µF capacitor comes from the same place:....
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This circuit greatly expands upon the capabilities of circuit 02. A thermocouple signal is quite small, and the long thermocouple leads often induce quite a bit of noise into the system. This new circuit is far more accurate, stable, and less immune to....
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The circuit doubles tbe frequency of a digital signal by operating on botb signal edges. Each transition causes exclusive-OR gate IC1 to produce a pulse, which clocks flip-flop IC3 after propagating through buffers IC2C and IC2B. Ifyou remove capacitor Cl,....
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Once again, this is a project designed by David Sayles. The input can be from a longwire or a loop antenna. The unit covers MW and Sw to 30MHz. Click here for a picture of David`s MW loop. Click here to view a finished picture of this project...
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Sensing circuit detects either steady or fluctuating air flows. The heart of the circuit is a Radio Shack piezo buzzer (P/N 273-060) and an LM324 quad op amp. (Red wire from the piezo element connects to capacitor CI, and the black wire to ground) When a....
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When this car alarm circuit is activated it stays activated for 80 seconds. It has 15 seconds delay for the driver to enter and deactivate. and All timmings can be altered easilly.....
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I tried to design a timer that would do everything it needed to do but with the smallest number of pieces and simplest mode of operation. It only needs the PIC, a four digit LED display, one other IC, a resistor network, one pushbutton switch and a....
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This is a 4 digit decimal counter which can operate as a free running counter or in count and hold mode with manual reset. In either mode the counter can be preset to count to a specified value. Clock edge and leading zero suppression can also be....
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The character data and command from the microcontroller is transferred serially to a shift register (74HC595), and the parallel output from the shift register is fed to LCD pins. 74HC595 is a high-speed 8-bit serial in, serial or parallel-out shift register....
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Channel Relay Board is a simple and convenient way to interface 8 relays for switching application in your project. Input - 12 VDC @ 336 mA. Output - eight SPDT relay. Relay specification - 5 A @ 230 VAC. Trigger level - 2 ~ 5 VDC. Berg pins for connecting....
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This project has two features. It will let you know when a single phone is using the line and also when two phones are on the line!
The green LED indicates the first phone and the red LED indicates the second phone! There are many times when you need to....
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This simple circuit is sure to have the police beating a path to your door - however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat. The circuit transmits on Medium Wave (this is the small....
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The circuit, built around a single integrated circuit (Ul, an MC3403P quad op amp), three transistors (Q1-Q3), and a few support components,.receives its input from the antenna (ANT1). The signal is fed through a high-pass filter, formed by CI, C2, and Rl,....
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The happy-birthday singer is a two bit wide by n words deep programable sequencer with 4 commands: reset to start vector (00), decrease frequency (01),increase frequency (10), and pause (11). The device starts out with a 2 word vector jump at the start of....
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Using a Quad NAND Gate, the TTL oscillator can use fundamental crystals between 1 and 10 MHz. The sine..
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This circuit allows a 4-to 20-mA current loop to control an isolated SCR drive. IC1A and are one-shots. Q2 detect..
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In this circuit, integration is performed by using a conventional operational amplifier and feedback capacitor, CF. When the integrator's output crosses the nominal threshold level at pin 6 of the LM131, the timing cycle is initiated. The average current fed....
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The timer interval starts when power is applied to circuit and terminates when voltage is applied to load. 2N2646 is used in oscillator which pulses base 2 of D5K..
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A simple rotating display. Just spin and enjoy. While the "Air display" is rotating, it writes the message on the air. Because the "persistence of the vision", you will be able to read the message. The operation is super simple and you don't need an user....
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This simple audio power amplifier was originally designed for a circuit board workshop, conducted by the OSU IEEE Student Group. At the workshop, 20 participants each constructed this amplifier, by etching and drilling the single sided circuit board,....
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This digital volume control has no pot to wear out and introduces almost no noise in the circuit. Instead, the volume is controlled by pressing UP and DOWN buttons. This simple circuit would be a great touch to any home audio project...
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Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and....
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This is a variable voltage 1.5A supply I threw together for bench experimenting for under $10. With a 24VDC wall wart, this board can produce anywhere from 23V to 1.2V..
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When the lines SDA (Serial DAta) and SDA 'are logical '1', the circuit is at rest with the result that optocouplers IC 1 and IC2 can not convey absolutely no information. But once the SDA line become the 'O', then the LED the IC 1 becomes conductive through....
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This illustrates another application in which the hookup versatility of a sample-and-hold often elimi nates the need for a separate op amp and a sampleand- hold module. ..
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The range of this ac-voltage monitor is 100 to 140 Vac, with a resolution of 1 V. The speech processor interprets an 8-bit binary input code from an analog-to-digital converter. The processor"s pulse-code-mod ulated output then passes through a filter and....
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A schematic diagram for the remote analyzer is shown. The circuit is powered from a simple 5-V supply, consisting of PL1, SI, Tl, a bridge rectifier (comprised of D1 through D4), capacitor CI, and a common 5-V regulator, Ul. Switch SI is the on/off control....
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This circuit is operating the room illuminates. The basic component of the circuit is a IC1 (CD4017). Push buttons room are connected by normally wired to the circuit. All circuit is separately by optocoupler, which means that the circuit is immune to....
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While the normal PC hardware might well run with just Tx, Rx and Ground connected, most driver software will wait forever for one of the handshaking lines to go to the correct level. Depending on the signal state it might sometimes work, other times it might....
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This Design Idea offers a solution to the challenge of turning devices on or off in the past. In Figure 1, IC2 is a 555-type timer (preferably CMOS) connected as a monostable one-shot multivibrator. The pushbutton switch, S1, triggers IC2. You can replace....
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This design measures the differential temperature between two sensors. Sensor Tl, located before the heater resistor, assumes the fluid"s temperature before it is heated by the resistor. Sensor TZ picks up the temperature rise induced into the fluid by the....
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I've seen an NE592 used as a video buffer amp at the end of a 75 ohm line. Used so that the 75 ohm line could drive all kinds of neat processing stuff without affecting the signal (that's what a buffer is after all, right?) Now National Semiconductor makes....
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This antenna might help to reduce power-line noise. A plastic hula hoop or conduit 3 feet in diameter, covered with aluminum foil as a shield is used for LI and L2. LI is two turns and L2 is one turn, threaded through the loop. SI selects 160- or 80-m....
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This circuit is very basic to build and puts out great power for your car or home. Keep all leads as short as possible...
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This is an image Schematic. No Description available...
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This receiver is capable of better than 1.5 p, VIHF sensitivity and uses MOSFET front-end circuitry with varactors to eliminate conventional bulky tuning capacitors. It also features high dynamic range, ceramic i-f filters requiring no alignment, and a....
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About twenty five years ago, an inventor friend of mine showed me some illustrations in a college physics book. The book was one of a three volume collection of physics lectures given by the noble prize winner Richard Feynman. The book illustration was very....
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The simple circuit in Figure 1 uses a low-current-drain MAX4073H amplifier to sense the current flowing through a 4- to 20-mA loop. The circuit senses the current through a 1 resistor with a fixed gain of 100 and uses no battery or dc power supply. The low....
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Here is a handy zener diode tester which tests zener diodes with breakdown voltages extending up to 120 volts. The main advantage of this circuit is that it works with a voltage as low as 6V DC and consumes less than 8 mA current. The circuit can be fitted....
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The laser light detector utilizes a sensitive photo transistor (Q5) placed at the focal point of a lens (LE2). The output of Q5 is fed to a sensitive amplifier consisting of array (Al) and is biased via the voltage divider consisting of R14 and Rl. The base....
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The following circuit is an example how to get power from RS-232 serial port. It gives regulated +5V power for logic circuits and also unregulated positive and negative power supplies for RS-232 transmitting circuit. The circuit gives only few milliampres....
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This circuit will flash a super-bright LED (5000+ mcd). Good for fake car alarm or other attention getting device. Component values are not critical, try anything else first from your junkbox. Obviously, the 470 ohm resistor (R3) determines the LED's....
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The original FLED-based SE uses a flashing LED to drive a type 1 solar engine (you`ll note that it`s just like the Zener-based SE, but with a FLED in the starring role). The good news is that all the parts in this solar engine are relatively easy to find;....
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Where N is the binary number from 0 to 15 formed by the digital input. If the analog input is a fixed de reference, the circuit is a conventional 4-bit D to ac signal, in which case the output is the product of the analog signal and the digital signal. The....
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The silicon controlled rectifier (SCR) is rated to handle at least the current of the power supply. It is connected in parallel across the 12 V dc output lines, but remains inert until a voltage appears at the gate terminal. This triggering voltage is....
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One of my prize pieces of equipment is a pair of Sony C-37A large capsule tube, condenser microphones. I bought these from the radio station at college because they were getting hard to use, and an intermittent connector problem resulted in a nasty....
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Below is a rough schematic of the layout of the accelerometer PC board looking from the component side. The microcontroller is an Atmel AT89S8252, an 8051 clone. This microcontroller is in-circuit programmable using an SPI interface. The SPI pins are also....
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Using dual flip-flop IC CD4027 employ a 555 based monostable circuit to supply input clock pulses. The circuit described here obviates this requirement. One of the two flip-flops within IC CD4027 itself acts as square wave shaper...
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The proximity sensor works on the principle of transmitting a beam of modulated infra-red light from the emitter diode LED2, and receiving reflections from objects passing in front of the beam with a photodiode detector Dl..
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An FM radio generates an interference signal that can be picked up on another FM radio tuned 10.7 MHz above the first one. The 50-k0 potentiometer adjusts the modulation level to maximum without distortion. The RC network improves the fidelity of the....
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SMASH is the Reference Platinum Simulator enabling truthfully the combination of digital, logic and analog multi-domain modeling as well as Instruction Set simulation (ISS) with no need for a "cosimulation backplane". Each of its successive releases....
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The microprocessor sends out an 8-bit binary code on its 8-bit I/O bus (the binary value needed to program the ICM7240), followed by four WRITE pulses into the CD4017B decade counter. The first pulse resets the 8-bit latch, the second strobes the binary....
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This circuit, shown symmetrically, divides an input by virtually any odd number. The circuit counts n + 1/2 clocks twice to achieve the desired divisor. By selecting the proper n, which is tbe decoded output of the LS161 counter, you can obtain divisors....
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A good way to mount the circuit board is to use a hot glue gun to "mold" the circuit underneath the lamp housing. There is plenty of space there for your board. At the next photos you can see the circuit board mounted on the small 31cm IKEA Mylonit Lamp.....
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This is just one of the many bugging devices available on the eaves-dropping market. The range includes pen and pencil holders, trophies, framed pictures and office furniture with false bottom drawers.
These products are readily sold to fledgling companies,....
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Integrating analog-to-digital converters (ADCs) provide high resolution analog-to-digital conversions, with good noise rejection. These ADCs are ideal for digitizing low bandwidth signals, and are used in applications such as digital multi-meters and panel....
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The amplifier is based on the commonly used class-AB complementary power amplifier with compound pair output transistors. The system uses a TL074 quad opamp to drive the output transistors. As can be seen from figure 1, A2 is used to set the voltage gain of....
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Electronic potentiometer using a standard CMOS logic and analog multiplexers. Pot have low distortion (0.005% less at 1 V rms) and is it easy for beginers to Understanding. In the beginning the art Hi-Fi when in the absence of high-quality potentiometers for....
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The operation of the circuit is like an enabled inverter, that is, the output Y = B provided A is high. If A is low, output is low (independent of the state of B). When the signals A and or B1 are connected to the inputs A and of this gate the output Y is....
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This inexpensive dc supply-voltage monitor sounds a warning when the voltage falls below a preset value. It is ideal for monitoring rechargeable batteries since it draws only a few microamperes when not sounding. The voltage at which the alarm sounds is....
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This regulated power supply was built as a simplified outboard version of a PSU in my first phono stage. Replacing hexfreds with tube rectifier eliminates the need for power-on sequencing. Chassis (salvaged from a hospital laser PSU) size is 180W*240D*100H....
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This circuit will detect a missing pulse or abnormally long spacing between consecutive pulses in a train of pulses. The timer is connected in the monostable mode. The time delay should be set slightly longer than the timing of the input pulses. The timing....
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A quad comparator forms the basis of a frequency detector that is faster and less expensive than more complex versions designed around frequency-to-voltage converter chips. Positive feedback through a 5MO resistor allows the circuit to resolve changes as....
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To calculate the length of the elements of other bands use the above formula. Example 6 meter band (50Mhz): (75/50)*0.96=1.44 meters..
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Described here is a simple omnidirectional, vertically-polarised dipole for two metres. Made from coaxial cable, it can be rolled up and stored in a small container. It may be used as is indoors, or waterproofed for use outside. No extravagant gain claims....
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This project uses the 1.2v rechargeable battery and solar panel from a Solar Garden Light. These lights can be bought for less than $5.00 in most $2.00 shops or similar shops that sell general household items.
We are also using the housing for this project....
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This simple circuit from the May 1996 Think Tank column of Popular Electronics activates a relay when it senses a composite video signal. This allows you to use the tuner built into your VCR to turn on and off older TVs that are not equipped with a remote.....
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Because the transconductance of an operational transconductance amplifier is directly proportionai to /ABc. the amplification of a signal can be controlled easily. The output current is the product from transconductance X input voltage. The circuit is....
This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the....
IC1 contains several oscillators and an amplifier. The low-frequency audio-signal oscillator is used to supply an input to the amplifier. That signal is the audio tone that is amplified, then supplied to the speaker by the amplifier. The high-frequency....
The circuit is based on a simple inductor-capacitor filter circuit, and needs only a pot and a small light bulb to set and stabilise the oscillation. The frequency is fixed, and with a good inductor should be capable of very low distortion. This circuit is....
If you are busy and cannot answer or do not wish to answer your phone, this circuit will give a busy signal without you ..
This circuit keeps an automobile's headlights on temporarily. It also will turn the lights off, even if you forget to flip the light switch. The circuit's shut-off delay is actuated only after both the ignition and light switches have been on, and only if....
Rectangular pulse generators, even at high frequencies, are easy to design. However, the design becomes more difficult if you need a signal that contains a precise number of periods with a sinusoidal shape. Although it is easy to produce a good sine wave,....
The circuit provides three square wave outputs with 120° of phase difference between each other. Reference clock frequency is twice that of the required frequency. This can be obtained from a crystal oscillator with a chain of dividers or by using LM 555 in....
This is a voltage controller oscillator that was designed as a wide range oscillator to generate clock pulses for a stepper motor drive system. It does however have some interesting features. The original application used a stepper motor for its ability to....
This signal generator uses a three channel DAC to generate Composite video signal (CVBS) and S video signal (Y/C separated) at the same time, left one channel is not used in NTSC format. It is assigned for one of the color components of Y/CB/CR video format...
These circuits could be used as the basis for Model Railroad DCC Boosters or PWM motor controllers. The first schematic is for a basic 3 Amp - DCC Booster using the LMD 18200 CMOS, H-Bridge. Included in the design is a 5Volt regulator that supplies....
A center-tapped 240-V transformer is used with two SCR devices to provide rectified ac (pulsating dc) to MOT1...
This rf power switch operates at 1. 7 MHz with a 50-V source and load. Its on loss is 0.2 dB and its off isolation is 30 dB. It provides 40-W PEP, 45 VrEAK and 0.9 APEAK· The control input can come from CMOS, TTL, LS, etc., ..
Here are some utility circuits for use with the Ramsey FM10a, and other small FM stereo transmitter kits. This information may be helpful for setting up a micro powered FM radio station. The FM10a and similar kits tend to put out a low quality, broad band....
This is a sensitive, mini-powered FM transmitter consisting of an rf oscillator section interfaced with a high-sensitivity wide passband audio amplifier and capacitance microphone with built-in FET that modulates the base of the rf oscillator transistor.....
This circuit was inspired by a friend who wanted a reberb for his portable guitar amplifier. I originally tried using NE5532 low noise op-amps for the buffer stages but they were too noisy for the low level circuits so I switched to discrete 2N3904....
On most FM tuners, the stereo indicator lights upon detection of the 19-kHz pilot tone. However, this doesn"t mean that the program is actually stereophonic, since the pilot tone is often transmitted with mono programs also. A similar situation exists on....
Two NAND gates are used for the oscillator, and two as the control. If the two-tone speed needs to be altered, the 220 µ capacitors can be changed Oarger for slower operation). If the frequency of the oscillator is to be changed, the 0.2 and 0.1 /iF....
In this configuration, the display reads hertz directly. With pin 11 of the ICM7027 A connected to V00, the gating time will be 0.1 second; this will display tens of hertz as the least significant digit. ..
The circuit consists of ICM7208 seven-decade counter U1, ICM7207A oscillator controller U2, and CA3130 biFET op amp U3. IC U1 counts input signals, decodes them to 7-segment format, and outputs signals that are used to drive a 7-digit display. IC U2....
The modulator and oscillator consist of two NPN transistors. The base of the modulator transistor is driven by a bidirectional current source with the voltage range for the high condition limited by a saturating PNP collector to the pin 4 Vreg voltage and....
Reverse engineered circuit diagram of a popular retail doorknob alarm. It contains a small transmitter and the doorknob acts as an antenna so it will not work on a metal door. When a person comes close to the doorknob this loads down the oscillator and the....
The variable voltage regulator lets you adjust the output voltage of a fixed de power supply between 1.2 and 37 V de, and will supply the output current in excess of 1.5 A. The circuit incorporates an LM117K three-terminal adjustable output positive....
This circuit provides accurate full-wave rectification. The output impedance is low for both input polarities, and the errors are small at all signal levels. Note that the output will not sink heavy currents, except a small amount through the 10-K!J....
Many beginners trying out their skill with QRP TX, for the first time have to overcome many problems before they are able to come on the air. On usual complaint is that, every thing is working fine but the signal is not going out. Here is a simple set up....
This is an experimental work to monitor a spectrum pattern of radio band, and is a continuous project from Audio Spectrum Monitor. To analyze the spectrum of an input signal, I chose an Atmel`s AVR microcontroller used in Audio Spectrum Monitor to process....
The crystal used in the topology of Figure 1 can be either a fundamental AT-CUT or BT-CUT. A BT-CUT crystal has poor frequency stability over temperature compared to an AT-CUT. This topology uses a parallel crystal and not a series crystal...
The 24 watt amp is easy to build, and very inexpensive. The circuit can be used as a booster in a car audio system, an amp for satellite speakers in a surround sound or home theater system, or as an amp for computer speakers. The circuit is quite compact and....
The simplest of all motor controllers (besides a straight on/off switch) is the contactor controller. I designed this contactor controller for use in my electric scooter project. It is based around three 12V relays, two 12V batteries, two switches and of....
Easy to build, this high voltage generator is capable of generating up to 50KV but the breakdown voltage of the coil limits the voltage to a value somewhat lower. T2 is the ignition coil of a car and also the 0.5µF capacitor comes from the same place:....
This circuit greatly expands upon the capabilities of circuit 02. A thermocouple signal is quite small, and the long thermocouple leads often induce quite a bit of noise into the system. This new circuit is far more accurate, stable, and less immune to....
The circuit doubles tbe frequency of a digital signal by operating on botb signal edges. Each transition causes exclusive-OR gate IC1 to produce a pulse, which clocks flip-flop IC3 after propagating through buffers IC2C and IC2B. Ifyou remove capacitor Cl,....
Once again, this is a project designed by David Sayles. The input can be from a longwire or a loop antenna. The unit covers MW and Sw to 30MHz. Click here for a picture of David`s MW loop. Click here to view a finished picture of this project...
Sensing circuit detects either steady or fluctuating air flows. The heart of the circuit is a Radio Shack piezo buzzer (P/N 273-060) and an LM324 quad op amp. (Red wire from the piezo element connects to capacitor CI, and the black wire to ground) When a....
When this car alarm circuit is activated it stays activated for 80 seconds. It has 15 seconds delay for the driver to enter and deactivate. and All timmings can be altered easilly.....
I tried to design a timer that would do everything it needed to do but with the smallest number of pieces and simplest mode of operation. It only needs the PIC, a four digit LED display, one other IC, a resistor network, one pushbutton switch and a....
The character data and command from the microcontroller is transferred serially to a shift register (74HC595), and the parallel output from the shift register is fed to LCD pins. 74HC595 is a high-speed 8-bit serial in, serial or parallel-out shift register....
Channel Relay Board is a simple and convenient way to interface 8 relays for switching application in your project. Input - 12 VDC @ 336 mA. Output - eight SPDT relay. Relay specification - 5 A @ 230 VAC. Trigger level - 2 ~ 5 VDC. Berg pins for connecting....
This project has two features. It will let you know when a single phone is using the line and also when two phones are on the line! The green LED indicates the first phone and the red LED indicates the second phone! There are many times when you need to....
This simple circuit is sure to have the police beating a path to your door - however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat. The circuit transmits on Medium Wave (this is the small....
The circuit, built around a single integrated circuit (Ul, an MC3403P quad op amp), three transistors (Q1-Q3), and a few support components,.receives its input from the antenna (ANT1). The signal is fed through a high-pass filter, formed by CI, C2, and Rl,....
Using a Quad NAND Gate, the TTL oscillator can use fundamental crystals between 1 and 10 MHz. The sine..
This circuit allows a 4-to 20-mA current loop to control an isolated SCR drive. IC1A and are one-shots. Q2 detect..
In this circuit, integration is performed by using a conventional operational amplifier and feedback capacitor, CF. When the integrator's output crosses the nominal threshold level at pin 6 of the LM131, the timing cycle is initiated. The average current fed....
The timer interval starts when power is applied to circuit and terminates when voltage is applied to load. 2N2646 is used in oscillator which pulses base 2 of D5K..
A simple rotating display. Just spin and enjoy. While the "Air display" is rotating, it writes the message on the air. Because the "persistence of the vision", you will be able to read the message. The operation is super simple and you don't need an user....
This simple audio power amplifier was originally designed for a circuit board workshop, conducted by the OSU IEEE Student Group. At the workshop, 20 participants each constructed this amplifier, by etching and drilling the single sided circuit board,....
This digital volume control has no pot to wear out and introduces almost no noise in the circuit. Instead, the volume is controlled by pressing UP and DOWN buttons. This simple circuit would be a great touch to any home audio project...
Any number of normally open switches may be used. Fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to protect removable panels and....
When the lines SDA (Serial DAta) and SDA 'are logical '1', the circuit is at rest with the result that optocouplers IC 1 and IC2 can not convey absolutely no information. But once the SDA line become the 'O', then the LED the IC 1 becomes conductive through....
This illustrates another application in which the hookup versatility of a sample-and-hold often elimi nates the need for a separate op amp and a sampleand- hold module. ..
The range of this ac-voltage monitor is 100 to 140 Vac, with a resolution of 1 V. The speech processor interprets an 8-bit binary input code from an analog-to-digital converter. The processor"s pulse-code-mod ulated output then passes through a filter and....
A schematic diagram for the remote analyzer is shown. The circuit is powered from a simple 5-V supply, consisting of PL1, SI, Tl, a bridge rectifier (comprised of D1 through D4), capacitor CI, and a common 5-V regulator, Ul. Switch SI is the on/off control....
This circuit is operating the room illuminates. The basic component of the circuit is a IC1 (CD4017). Push buttons room are connected by normally wired to the circuit. All circuit is separately by optocoupler, which means that the circuit is immune to....
While the normal PC hardware might well run with just Tx, Rx and Ground connected, most driver software will wait forever for one of the handshaking lines to go to the correct level. Depending on the signal state it might sometimes work, other times it might....
This design measures the differential temperature between two sensors. Sensor Tl, located before the heater resistor, assumes the fluid"s temperature before it is heated by the resistor. Sensor TZ picks up the temperature rise induced into the fluid by the....
I've seen an NE592 used as a video buffer amp at the end of a 75 ohm line. Used so that the 75 ohm line could drive all kinds of neat processing stuff without affecting the signal (that's what a buffer is after all, right?) Now National Semiconductor makes....
This antenna might help to reduce power-line noise. A plastic hula hoop or conduit 3 feet in diameter, covered with aluminum foil as a shield is used for LI and L2. LI is two turns and L2 is one turn, threaded through the loop. SI selects 160- or 80-m....
This circuit is very basic to build and puts out great power for your car or home. Keep all leads as short as possible...
This receiver is capable of better than 1.5 p, VIHF sensitivity and uses MOSFET front-end circuitry with varactors to eliminate conventional bulky tuning capacitors. It also features high dynamic range, ceramic i-f filters requiring no alignment, and a....
Here is a handy zener diode tester which tests zener diodes with breakdown voltages extending up to 120 volts. The main advantage of this circuit is that it works with a voltage as low as 6V DC and consumes less than 8 mA current. The circuit can be fitted....
The laser light detector utilizes a sensitive photo transistor (Q5) placed at the focal point of a lens (LE2). The output of Q5 is fed to a sensitive amplifier consisting of array (Al) and is biased via the voltage divider consisting of R14 and Rl. The base....
The following circuit is an example how to get power from RS-232 serial port. It gives regulated +5V power for logic circuits and also unregulated positive and negative power supplies for RS-232 transmitting circuit. The circuit gives only few milliampres....
This circuit will flash a super-bright LED (5000+ mcd). Good for fake car alarm or other attention getting device. Component values are not critical, try anything else first from your junkbox. Obviously, the 470 ohm resistor (R3) determines the LED's....
The original FLED-based SE uses a flashing LED to drive a type 1 solar engine (you`ll note that it`s just like the Zener-based SE, but with a FLED in the starring role). The good news is that all the parts in this solar engine are relatively easy to find;....
Where N is the binary number from 0 to 15 formed by the digital input. If the analog input is a fixed de reference, the circuit is a conventional 4-bit D to ac signal, in which case the output is the product of the analog signal and the digital signal. The....
The silicon controlled rectifier (SCR) is rated to handle at least the current of the power supply. It is connected in parallel across the 12 V dc output lines, but remains inert until a voltage appears at the gate terminal. This triggering voltage is....
One of my prize pieces of equipment is a pair of Sony C-37A large capsule tube, condenser microphones. I bought these from the radio station at college because they were getting hard to use, and an intermittent connector problem resulted in a nasty....
Below is a rough schematic of the layout of the accelerometer PC board looking from the component side. The microcontroller is an Atmel AT89S8252, an 8051 clone. This microcontroller is in-circuit programmable using an SPI interface. The SPI pins are also....
Using dual flip-flop IC CD4027 employ a 555 based monostable circuit to supply input clock pulses. The circuit described here obviates this requirement. One of the two flip-flops within IC CD4027 itself acts as square wave shaper...
The proximity sensor works on the principle of transmitting a beam of modulated infra-red light from the emitter diode LED2, and receiving reflections from objects passing in front of the beam with a photodiode detector Dl..
An FM radio generates an interference signal that can be picked up on another FM radio tuned 10.7 MHz above the first one. The 50-k0 potentiometer adjusts the modulation level to maximum without distortion. The RC network improves the fidelity of the....
The microprocessor sends out an 8-bit binary code on its 8-bit I/O bus (the binary value needed to program the ICM7240), followed by four WRITE pulses into the CD4017B decade counter. The first pulse resets the 8-bit latch, the second strobes the binary....
This circuit, shown symmetrically, divides an input by virtually any odd number. The circuit counts n + 1/2 clocks twice to achieve the desired divisor. By selecting the proper n, which is tbe decoded output of the LS161 counter, you can obtain divisors....
A good way to mount the circuit board is to use a hot glue gun to "mold" the circuit underneath the lamp housing. There is plenty of space there for your board. At the next photos you can see the circuit board mounted on the small 31cm IKEA Mylonit Lamp.....
This is just one of the many bugging devices available on the eaves-dropping market. The range includes pen and pencil holders, trophies, framed pictures and office furniture with false bottom drawers. These products are readily sold to fledgling companies,....
The amplifier is based on the commonly used class-AB complementary power amplifier with compound pair output transistors. The system uses a TL074 quad opamp to drive the output transistors. As can be seen from figure 1, A2 is used to set the voltage gain of....
Electronic potentiometer using a standard CMOS logic and analog multiplexers. Pot have low distortion (0.005% less at 1 V rms) and is it easy for beginers to Understanding. In the beginning the art Hi-Fi when in the absence of high-quality potentiometers for....
The operation of the circuit is like an enabled inverter, that is, the output Y = B provided A is high. If A is low, output is low (independent of the state of B). When the signals A and or B1 are connected to the inputs A and of this gate the output Y is....
This inexpensive dc supply-voltage monitor sounds a warning when the voltage falls below a preset value. It is ideal for monitoring rechargeable batteries since it draws only a few microamperes when not sounding. The voltage at which the alarm sounds is....
This regulated power supply was built as a simplified outboard version of a PSU in my first phono stage. Replacing hexfreds with tube rectifier eliminates the need for power-on sequencing. Chassis (salvaged from a hospital laser PSU) size is 180W*240D*100H....
This circuit will detect a missing pulse or abnormally long spacing between consecutive pulses in a train of pulses. The timer is connected in the monostable mode. The time delay should be set slightly longer than the timing of the input pulses. The timing....
A quad comparator forms the basis of a frequency detector that is faster and less expensive than more complex versions designed around frequency-to-voltage converter chips. Positive feedback through a 5MO resistor allows the circuit to resolve changes as....
Described here is a simple omnidirectional, vertically-polarised dipole for two metres. Made from coaxial cable, it can be rolled up and stored in a small container. It may be used as is indoors, or waterproofed for use outside. No extravagant gain claims....
This project uses the 1.2v rechargeable battery and solar panel from a Solar Garden Light. These lights can be bought for less than $5.00 in most $2.00 shops or similar shops that sell general household items. We are also using the housing for this project....
This simple circuit from the May 1996 Think Tank column of Popular Electronics activates a relay when it senses a composite video signal. This allows you to use the tuner built into your VCR to turn on and off older TVs that are not equipped with a remote.....
Because the transconductance of an operational transconductance amplifier is directly proportionai to /ABc. the amplification of a signal can be controlled easily. The output current is the product from transconductance X input voltage. The circuit is....
