Top Circuits Page 27
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The circuit has two ranges: 10 sees to 5 mins and 1 min to 80 mins. It can be powered by a 9-V battery. With the LED connected as shown a reasonable frequency of flashing occurs throughout the range of operation. ..
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Those of you who frequently use devices that work on battery or you need a negative trend at the moment you have a single positive, will definitely look for a converter like the one described below. Constructing it, you can convert a positive voltage of a....
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The circuit provides for accurate half-wave rectification of the incoming signal. For positive signals, the gain is 0; for negative signals, the gain is -1. By reversing both diodes, the polarity can be inverted. This circuit provides an accurate output, but....
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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 project was designed and constructed as enhancement to the 0-30V Stabilized Power Supply Project with the DIY electronics hobbyist in mind. The circuit uses a single PIC Microchip to perform the Voltage, Current and Temperature conversions and display....
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This microcontroller fascinated me a lot because I wanted to see what we can do with an 8-pin microcontroller (out of which 2 pins goes to power supply, so actually just 6-pins are left for I/O). So I thought of making my own learning board for this. In this....
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A simple X-band radar detector is capable of indicating changes in rf radiation strength at levels down to 2 mW/cm2. Radiation falling on the detector diode, produces a voltage at the input of an amplifier whose gain may be adjusted to vary the range at....
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The relay which applies power to the wiper motor is actuated at periodic intervals by the timer circuit, closing the wiper motor contacts. Potentiometer R1 serves as the pulse rate control and potentiometer R5 as the pulse width control. ..
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U1 is configured to operate in the standard astable mode, providing a form of relaxation oscillator. When power is applied, C2 initially charges through Rl, R2 and R3 to two-thirds of the supply voltage. At that point, U1 senses that its threshold voltage at....
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In battery-powered applications in which power management is key, a microprocessor may adjust its core voltage corresponding to an increase or a decrease in clock speed, allowing full processing power when necessary but not wasting excess power when idle.....
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Charge redistribution to achieve A/D conversion. In typical applications, as a ratiometric conversion system for a microprocessor, V^p, will be connected to ground and VREF+ will be connected to Vcc.
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This diagram shows a high speed data acquisition system with 8 differential inputs and 12-bit resolution using the AM-543. If the control logic is timed so that the Sample-Hold-ADC section is converting one analog value while the mux-amplifier section is....
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This GAL programmer is controlled via a parallel port, so that any exclusive interface is not requires for the programmer. It is easy to use on the notebook PCs. When program a PIC, a socket converter is needed. After assembly is finished, check if the....
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Transistor Ql, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips. The output from the oscillator is then rectified by the two 1N4148 diodes and filtered by....
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Care must be taken to eliminate any stray currents from flowing into the current summing node. This can be accomplished by forcing all points surrounding the input to the same potential as the input. In this case the potential of the input is at virtual....
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This method is capable of measuring phase between 0 to ±180°. The generated square waves A and are fed to a D flip-flop which gives an output C equal to logic 1 when input 1 leads input 2 and equal to logic 0 in case of lagging. When C = logic 0, the....
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The tester gives an audible indication, making it unnecessary for the user to look directly at the instrument to observe a meter reading. In addition, the current and voltage of the tester are strictly limited. It can apply no more than 0.6 volts dc and no....
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The shift pulse turns off the conducting scs by reverse biasing the cathode gate. The charge stored on the coupling capacitor then triggers the next stage. An excessively long shift pulse charges up all the capacitors, turning off all stages.
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A straightforward circuit using a LM311 for the level detector and a CMOS analog gate to discharge the capacitor is shown. An important property of this type of counter is the ease with which the count can be changed; it is only necessary to change the....
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The display shows each increment. By using mode 2, external debouncing of the gate switch is unnecessary, provided the switch bounce is less than 35ms. The 3 V lithium battery can be replaced without disturbing operation if a suitable capacitor is connected....
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Here is a design that you can own, tailor to your specific
needs, layout on your circuit board and put on your bill of
materials. Finally, you will be in control of the black magic
(and high voltages) of ring-tone generation...
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This project has been specially designed to introduce you to SMD (Surface Mount Devices). Surface Mount is really not new. It started as far back as 1940 with a hybrid circuit in a digital watch. A chip was cemented onto a slab of ceramic material having....
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Companies usually purchase one type of telephone for all employees, which is understandable, especially if they obtain a discount for buying in quantity. One ringer sound for everyone can pose a problem, though, if the sound of a ringing phone makes a dozen....
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This device consists of a ring detector connected to the telephone line. When the telephone rings, the ring detector impresses high-frequency pulses on the ac power line...
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The XR-T8205 Tone Ringer is primarily intended as a replacement for the mechanical telephone bell. The device can be.powered directly from telephone ac ringing voltage or from a separate dc supply. An adjustable trigger level is provided with an external....
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Both oscillators are built using MPF102 or J310 FETs. The Mixer is BF998 dual gate MOSFET. Audio IC amplifier is LM386 which drives a speaker. I have used a stabilized supply for two oscillators and mixer. U1, a 78L05 is doing this job nicely. ..
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This circuit is on oscillator with LI being a 4" diameter coil of 35 turns of #26 magnet wire. Metal in proximity to LI will cause the oscillator to shift frequency. An AM transistor radio is used to detect the frequency shift...
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Whoever thinks about reproducing an interface for the Aladin, should first of all be aware of the fact that there are two different versions of the interface. The first version, easier to assemble, enables the user to transfer dive data from the Aladin to....
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The Analog Interface Unit (AIU) is a simple circuit that connects to a PC parallel port, and allows you to sample and output 8-bit analog signals under software control...
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The CCD Array Reader project began with a free sample of the Texas Instruments TC102-1 CCD Linear Image Sensor and its rather terse data sheet. The TC102-1 provides virtually no support circuitry, only the raw CCD (with a few special pixels) and a simple....
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A simple circuit to connect the Dreamcast console to PC. No MAXxxx IC required. Only a few discrete components. This circuit is a direct replica of the daVinci cradle schematic:..
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I keep all rights to those circuits myself. You may freely build those circuits to yourself and your friends, but commercial use of those circuits is not allowed. NOTE: Those circuits are old designs from time when I was not so good in electronics than I am....
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The machine model, commonly used for ESD testing in Japan, is a more severe ESD test. This model simulates metallic contact between the device under test and a charged body. The source capacitor is 200pF with no limiting resistor. The higher source....
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The circuitry for a hot swappable PCI slot on a motherboard or backplane is shown in Figure 1. The power supplies for each PCI slot are controlled by an LTC1421 and four external FETs, and the data bus is buffered by several QS3384 QuickSwitches or....
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This is a programmable infrared (remote control) transmitter, which can be controlled from a PC serial port. It is capable of sending many remote control formats, including the Philips RC-5 standard. Exact formats with the timing parameter names are shown on....
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This is a simple, cheap device that can be connected to any serial port to control most components that have infrared remote controls. I designed and built it (on a solderless breadboard) in 1991. In 1992 I wrote a lengthy description of it for an....
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A standard serial interfacing for PC, RS232C, requires negative logic, i.e., logic `1` is -3V to -12V and logic `0` is +3V to +12V. To convert a TTL logic, say, TxD and RxD pins of the uC chips, thus need a converter chip. A MAX232 chip has long been using....
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There`re many, who built the Easy Programmer or C-52 Evaluation Board, asking for the RS232C level converter chip, DS275. Many have changed to MAX232 instead, because of not available in his home. Here is another simple and cheap circuit using small signal....
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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 device is a simple timer, allowing to keep on the headlights of your vehicle for about 1min. and 30sec., e.g. when accessing some dark place, without the necessity of coming back to switch-off the lights...
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This circuit must be connected to a 5 volt DC source. See my RR page for several 5 volt supplies. Note the flashing LED is optional, but looks s-o-o-o-o good on the top of a locomotive...
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The preamp circuit is completely conventional, and by necessity is AC coupled throughout. The artificial earth is derived by two resistors (R1 and R2), which will set the "earth" at exactly 1/2 the supply voltage. This is nominally 13.8V in all cars, since....
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Whenever I`m in the car listening to my favourite CD, it always happens-my batteries go dead. To solve that problem, I built this extremely simple regulator circuit. It steps down the 12V from the lighter socket to 9V which is used by the CD player.....
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Using a simple 741 amplifier connected as a current-to-voltage converter with the LED as the current source, the voltage at the output is proportional to incident light. The junction is Q biased only by the difference between the output summing node junction....
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Although white LEDs are common in a variety of lighting applications, their 3 to 4V forward-voltage drop makes low-voltage applications challenging. Charge pumps and other ICs are available for driving white LEDs, but they generally don`t work with the low....
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This is a spectacular but completely useless project. It lights Ultra-Bright LEDs in a sequence and each LED flashes brightly very briefly. The LEDs light-up going around and around since they are mounted in a circle (on a CD), then they pause before chasing....
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This electronic level uses two LED indicators instead of an air bubble. If the surface is tilted to the right, one LED lights; if it's tilted to the left, the other LED lights. When the surface is level, both LEDs light. It uses two unidirectional mercury....
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A tapped-coil Colpitis oscillator is used at Ql to provide four tuning ranges from 1.7 to 3.131Hz, 3.0 to 5.6 MHz, 5.0 to 12 MHz and 11.5 to 31 MHz. A Zener diode (D2) is used at Ql to lower the operating voltage of the oscillator. A small value capacitor is....
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Resistors Rl and R2 temperature-stabilize the NAND gates; they also ensure that the gates are in a linear region for starting. Capacitor CI is a dc block; it must have less than Vw ohm impedance at the operating frequency. The crystal runs in a....
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Light filtering through the finger tip is detected by the cadmium sulphide photoresistor CD1 which forms the feedback network for transducer amplifier section ICA producing a weak signal which is further amplified by ICB. This signal is now compared against....
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An RF input is applied to the primary of Tl, which applies equal amplitude, opposite phase RF drive for output FETs Ql and Q2. With no AF modulation at points A and B, the opposite phase RF signals cancel each other and no output appears at the 50 V output....
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When measure video signal with oscilloscope, video line selector is very useful to find a scan line. The line selecter generates trigger pulse at selected line, oscilloscope will display only selected line. This is a very simple video line selector...
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The amplifier in Figure 1 originally served as the photomultiplier preamplifier in a Doppler system intended for eventual operation in the Martian atmosphere. The design is based on a switchable array of six Maxim MAX4258 dual-channel video....
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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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Recently, most digital video equipments, such as video recorder, DVD player and TV game, have component video output. The component video signal is like RGB video signal, but it cannot connect to RGB monitor directly. Thus I designed and built YUV(YCrCb) to....
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The composite input signal is preamplified by transistor Ql and is then coupled to the high-pass filter composed of C3, C4, R6, and R7. The filtered audio is then passed to IC1, an MC1310P "Coilless Stereo Demodulator." That IC is normally used to demodulate....
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LDR1, a cadmium sulphide (CDS) photoresistive cell is used as the lower leg of a voltage divider between Vcc and ground. The timer terminals 2 and 6 are connected to the junction of the photocell and SENSITIVITY control Rl. The resistance of the....
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The three-channel amplifier output distribution uses a single TL084. The first step is to capacitive coupling with a p. 1.0 ~ electrolytic capacitor. The entries are railways Vee Y2 or 4.5 V. This allows using a single 9 V power supply A voltage gain of 10....
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The NE570 can be used to make a high performance compressor FTA, except that the rectifier is connected to the input. This makes gain inversely proportional to the input level so that a drop of 20 dB input level will produce an increase of 20 dB gain. The....
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The circuit can be used to simulate large capacitances using small value components. With the values shown and C - 10 µ¥, an effective capacitance of 10,000 µF was obtained. The Q available is limited by the effective series resistance.
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The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
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A touch-sensing circuit keeps the high-voltage generator cut off until something touches the fence wire. Contact with the fence sensing circuit wire starts the high-voltage generator which applies a series of 500 microsecond pulses at approximately 300 volts....
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The monitoring circuit consists of four tri-color LEDs driven by an equal number of op amps configured as gain-of-one inverting amplifiers. Each LED is wired in the circuit so that it glows red when the input to the op amp is high, and green when the input....
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To simplify the following schematics and facilitate easy understanding of the principles involved, the following schematic substitution is used (Note the triac driver is of limited use at 3 f voltage levels).
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The accuracy of direct linear coupling of analog current signals via an optocoupler is determined by the coupler linearity and its temperature coefficient. Use of an additional coupler for feedback can provide linearity only if the two couplers are perfectly....
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The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs. The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms. Lazar has adapted the sound card to use a common....
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This amplifier can amplify to 10dB the RF signal from antenna working as class A and is based on transistor BFQ34 of Philips. The transistor comes in case SOT122A. You may find the BFQ34T in market but better do not use it as it has different characteristics. ..
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DTMF (Dual Tone Multiple Frequency) is associated with digital telephony, and provides two selected output frequencies (one high band, one low band) for a duration of 100 ms. DTMF generation consists of selecting and combining two audio tone frequencies....
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The circuit illustrates feedback speed regulation of a standard ac induction motor, a function difficult to accomplish other than with a costly, generator type, precision tachometer. When the apertured disc attached to the motor shaft allows the light beam....
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A thermostat doesn't try to maintain a constant temperature. In order to do so - it would have to keep switching on and off every few seconds. Instead - it keeps the temperature within a specific range. When the preset temperature has been reached - it....
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In this circuit a non-locking push switch is used to activate a load. The load remains switched on until power is removed from the circuit. The load is represented by R5 and D1, but could be a lamp, a relay or another circuit. S2 breaks power to the circuit....
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To maintain an alarm condition when an overvoltage transient disappears, add an SCR to the comparator circuits. For SCR operation, voltages to the comparator inputs are inverted. (B) The triple-voltage monitoring circuit detects transient power-supply....
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The voltage to be compared is fed through diode Dl and D2 to the voltage dividers Rl and R5 where the low and high limits are present. When the voltage level of an input signal exceeds the high threshold limit set with potentiometer Rl, the diode Dl becomes....
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The switcher output goes to the single vertical input of the scope, and a sync line from one of the inputs is taken to the scope's external-sync input. Frequency response of the input amplifiers is 300 kHz over the range of the gain controls. ..
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By repetitively charging and discharging a capacitor through the primary of an induction coil with a high voltage, an ultra high emf is induced in the secondary. Switching is performed by the triac, triggered by the disc at times set by Cl and Rl. With a 12....
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For the outband decoder shown here to work, the cable company must provide at least a 1 millivolt signal. Values for C1-C5 and L1-L4 ore found In Table 1. This circuit consists of an amplifier for the synch channel and a video detector which controls an....
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This circuit consists of an amplifier and video detector with a second subcarrier detector for synch recovery purposes. A pulse-former circuit modulates the gain of the main channel increasing it during synch intervals. ..
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The circuit shown here with RC filter (Figure T). Micropoco capacitor has a temperature coefficient of 125 10"6 60.10" 6'C" V In simplified circuits a fixed resistor (e g. 620k) can be used for a guaranteed switching level of < l6mV.
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Al's positive input is biased by the thermocouple. Al's output drives a crude V — F converter, comprised of the 74C04 inverters and associated components. Each V — F output pulse causes a fixed quantity of charge to be dispensed into the 1 µ¥ capacitor....
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The JFET Pierce oscillator is stable and simple. It can be the clock of a microprocessor, a digital timepiece or a calculator. With a probe at the output, it can be used as a precise injection oscillator for troubleshooting.
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The DC output at Pin 1 vanes linearly with the RMS input at Pin 4. 2 CT is tweaked until the svnc signal is in phase with the AC signal. An ac voltmeter may be easily constructed. Simplicity of the circuit and low component count make it particularly....
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In these applications, a pulse input at % is differentiated by a C-R network and the negative-going edge at pin 6 causes the input comparator to trigger the timer circuit. Just as with a V-to-F converter, the average current flowing out of pin 1 is IaverAGE....
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The heart of the circuit is IC2, a 50240 top-octave generator. That device uses a single input-frequency to generate all twelve notes of the musical scale. The input signal is provided by IC1, a 4001 quad 2-input NOR gate. Two sections of that IC are used to....
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The electronic circuit in the VOX Box consists of three parts: a microphone preamplifier, a Schmitt trigger, and a relay driver. Input signals (MIC INPUT terminals) to the microphone preamplifier (Ul) are amplified and fed to a THRESHOLD control (R8). When....
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The waa-waa effect is achieved as certain frequencies are amplified more than others. A phase shift RC oscillator makes up the basic circuit. Negative feedback is obtained by feeding part of the signal back to the base. When adjusting initially, RV1 is....
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It seems that guitar fuzz boxes have been around since the beginning of rock, and have seen little improvement over the years. This one is somewhat different because rather than simply distorting the sound, it also pulses in step with the peaks of the....
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Three lights are controlled by the three channels. One light will pulse in response to the bass, another illuminates with mid-range sounds, and the last lights for high notes. Four level controls allow adjustment of overall light level and each channel....
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The circuit consists of separate amplifiers—one for each station—rather than a single amplifier and a time sharing arrangement. Ul and U2 are low-voltage audio amplifiers, each of which operates as separate entities with switches at either station....
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A low power, low cost dc lamp dimmer for a two-wire portable "flashlight" can be realized with little or no heatsinking. In addition, a single potentiometer, R3 adjusts lamp brightness. Battery power is stored in Cl for Ul, which is a free-running....
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This circuit is useful where fast signal acquisition and high precision are required, as in electronic scales. The filter's time constant is set by the 2 ohm resistor and the 1 µ capacitor until comparator No. 1 switches. The time constant is then set by....
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The op amp is connected in the inverting mode. Resistor R3 from the output to the inverting input sets the gain and current through the frequency-determining capacitor, CI. Capacitor C2 provides feedback from the output to the junction of Rl and R2. CI and....
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Tl and T2 are 600 to 8 ohm transformers (any transistor radio output transformers with 500 to 4 ohm impedance may be used). Ql is a 2N2222 npn transistor, and Q2 is a 2N2907 pnp transistor. Dl and D2 1N270 signal diodes (HEP 134 or 135). Two transistors,....
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The circuit requires only one dual-ganged potentiometer to tune over a wide range; if necessary over the entire audio range in one sweep. The principle used is that of the Wien bridge, fed from anti-phase inputs. The output should be buffered as shown with a....
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The circuit spectator interference enables implantation mono sound at any point between stereo speakers. When P1 is in the middle of his journey, there is strengthening or weakening of the mark the entrance to the exit in any of the two channels. When the....
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This circuit offers open and closed loop contacts (switches 1,2,3) that triggers the alarm ON and stays ON for 5 -10 minutes. The trigering delay (entrance/exit) is 27 seconds. This simple alarm circuit Has also a cancel button for reseting the circuit to....
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The circuit consists of Ql—a phototransistor that responds to an intensity of amplitude-modulated IR light source—and a three-stage, high-gain audio amplifier. Transformer Tl is used to match the output impedance of the receiver to today's popular....
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The pulse repetition rate is relatively insensitive to temperature, and power supply voltage and is a linear function of V1N, the modulating voltage. Useful information transfer was obtained in free air ranges of 12 feet (~ 4m). Greater range can also be....
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The eight SDI input stages use the new GENLINX¾II GS9024
Equalizer IC. Input Return Loss of the PCB is optimized by using
R-L circuits at each input. Each GS9024 performs high quality
signal equalization over a wide range of data rates from as low
as 30....
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There are two ways to program AVR-P40-USB:
with ICSP port and with JTAG port.
To program via ICSP port you need serial port or
parallel port AVR-ICSP programmer dongle
(Olimex part # AVR-PG1B or AVR-PG2B).
The serial port ICSP programmer (AVR-PG1B)....
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Arcing completes a circuit -- closes a system -- between two voltage potentials. When arcing occurs, two oppositely charged static voltage potentials can cancel each other out. The arcing problems that occur are usually between two electrically isolated....