Published:2009/6/19 1:42:00 Author:May
A telephone pick-up coil is used as a sensor for low-frequency magnetic fields. The signal is amplified and detected, then used to drive a comparator. (View)
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Published:2009/6/19 1:41:00 Author:May
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Published:2009/6/19 1:41:00 Author:May
An audio amplifier which operates off a +98-Vdc power supply (the rectified line voltage) is of-ten used in consumer products. The external high-voltage transistor, Q1, is biased and controlled by the LM3900. The magnitude of the dc biasing voltage, which appears across the emitter resistor of Q1 is controlled by the resistor. The resistor is placed from the (-) input to ground. (View)
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Published:2009/6/19 1:40:00 Author:May
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Published:2009/6/19 1:39:00 Author:May
This circuit is a general-purpose 10-W audio amplifier for moderate-power PA or modulator use in an AM transmitter. With higher voltages and a change in bias resistors, up to 30 W can be obtained. (View)
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Published:2009/6/19 1:38:00 Author:May
The system is formed by two separate circuits-a key and a keyhole. The key engages the key-hole with a mating pair of connectors. The key is a tone-generator circuit consisting of a 4049 hex in-verter CMOS IC (U1), switches (S1 and S2), a resistor (R1), and a capacitor (C1). The value of the tone generated by that circuit in Hz is determined by;The keyhole is a 567 tone-decoder circuit that can be conftgured to detect any frequency from 0.01 Hz to 500 kHz. The frequency it detects (fo), via the 567 IC, turns on the relay (K1). Compo-nents R3 and D1 are used to latch the circuit, so the output stays on even after the input tone is re-moved. When S2 is pressed, the system is reset. Switch S3 resets the circuit from inside. (View)
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Published:2011/4/14 1:32:00 Author:muriel | Keyword: rectification module, functional diagram
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Published:2009/6/19 1:37:00 Author:May
The power amplifiers, A2 and A3, are wired as followers and connected in parallel with the outputs coupled through equalization resistors. (View)
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Published:2009/6/19 1:37:00 Author:May
In this application, a BA1404 is used to generate an FM MPX baseband signal. This modulates a crystal oscillator (Q3) via a dual varactor series modulator. This transmitter can be to play CD audio on an existing FM auto radio. (View)
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Published:2009/6/19 1:36:00 Author:May
The heart of the circuit is a 4022 octal counter. When first powered up, C2 is charged via R5, so the reset input of the couitter is kept high. That causes output Qo to go high while all other outputs are low. With the switches wired as shown, when 54 is pressed, the BS170 is switched on via de-bouncing network R2/C1, and U1 receives a clock pulse. Also, C2 is discharged via R4 and D1 removing the reset signal of the counter, allowing it to advance. The time required for C2 to charge via R5 (e.g., to reset the counter), is the maximum time that can lapse before the next key is pressed.The above cycle is therefore repeated only if S8 (connected to the Q1 output) is pressed in time.When all keys have been pressed in time and in the correct order, Q7 goes high for about four sec-onds to drive the unlock circuitry (e.g., a relay driver for an automatic door opener. A builder can change the code by reviewing the switches. The code for the lock shown in the circuit diagram is 4-8-0-1-5-7-0. However, the 4022 octal counter can be replaced by a 4017 divide-by-10 counter. That will make it possible to add two more digits to the combination. (View)
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Published:2011/4/24 22:28:00 Author:muriel | Keyword: schematic circuit diagram
The figure shows a simplified schematic diagram of main circuit DMA12. It is mainly composed of input circuit and electromagnetic interference (EMI) filter circuit, impulse current limit circuit, the input rectifier filter circuit, the boost / power factor correction circuit and the absorption circuit, half-bridge power translation circuit, the output rectifier filter circuit. Compared with the DMA10, DMA12 uses single-phase input, boost/power factor correction method and lossless to absorb the buffer circuit, and the half-bridge DC / DC power conversion and output rectification filter part is the same with the DMA10.
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Published:2009/6/19 Author:May
Although ICs have largely replaced circuits such as this, this circuit still finds use where the flexibil-ity of a discrete device design is desirable. Parts are easy to obtain and the problem of IC obsoles-cence is eliminated. The TIP31A can be heatsinked to a small metal heatsink, if desired. (View)
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Published:2009/6/18 23:58:00 Author:May
A pulse-shaper is used in a tachometer cir-cuit to drive a meter. (View)
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Published:2009/6/18 23:57:00 Author:May
A true four-wire resistance measurement hookup. (View)
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Published:2009/6/18 23:57:00 Author:May
Use this circuit with a parabolic reflector microphone for eavesdropping on distant sounds. (View)
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Published:2009/6/18 23:56:00 Author:May
A three-terminal voltage regulator acts as a current source in this circuit. A resistor is being calibrated using a DMM and the current source. (View)
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Published:2009/6/18 23:56:00 Author:May
This input circuit will enable use of a high-impedance microphone where a low-impedance microphone would be needed. (View)
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Published:2009/6/18 23:56:00 Author:May
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Published:2009/6/18 23:55:00 Author:May
This preamp for RIAA phone use uses two op amps by Analog Devices. A switch selects compensation for moving magnet or rrtoving coil pickups. (View)
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Published:2009/6/18 23:55:00 Author:May
This simple power supply can be used in place of battery B1 of the 10-MHz frequency standard. (View)
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