Circuit Diagram

WIRELESS_GUITAR_TRANSMITTER

Published:2009/6/24 21:16:00 Author:Jessie

This transmitter has a built-in distortion effects unit and a touch switch to switch effects off and on. The circuit operates from a 9-V battery. IC1-a and IC1-b are used in the effects circuitry. IC1-d is an input preamp and IC2 is a quad analog switch to handle audio switching. Q1 acts as a varactor diode modulator while IC-4 is an 88- to 108-MHz FM oscillator.   (View)

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LOW_FREQUENCY_RELAY_OSCILLATOR

Published:2009/6/24 5:42:00 Author:May

Depending on the value of C and the resistance of the relay coil, and the difference in pull-in and drop-out voltage, this circuit will oscillate at a low frequency. R limits in rush current to capacitor C to a level that the relay contacts can handle. Typically, for a 400-Ω relay, R can be 20 to 440 ohms.Flash rate is approximately 1 cycle/second, depending on the relay.   (View)

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SIMPLE_TOUCH_SWITCH

Published:2009/6/24 21:05:00 Author:May

Q2 is held cut off since Q1 normally is conducting. When the touch plate is contacted by a large object (human body, etc.), stray 60-Hz pickup is rectified by D1 and D2, and produces a negative voltage across R2-C2 and the gate of Q1. Q1 cuts off, causes Q2 to conduct, and the output goes low.   (View)

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VARIABLE_WIEN_BRIDGE_OSCILLATOR

Published:2009/6/24 21:15:00 Author:Jessie

This circuit uses a single potentiometer to tune a 300- to 3000-Hz range. A FET op amp is used at A1 and A2. The upper frequency limit is determined by the gain-bandwidth product of the op amps.   (View)

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IONIZATION_CHAMBER_SMOKE_DETECTOR

Published:2009/6/24 21:15:00 Author:Jessie

Battery-operated, ionization chamber smoke detector includes a circuit to generate a unique alarm when the battery reaches the end of its useful life. The circuit uses the MCMOS MC14572 for two alarm oscillators (smoke and low battery). This circuit additionally uses five discrete transistors as buffers and comparators.   (View)

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FAST_TURN_ON_DELAYED_OFF_RELAY_CIRCUIT

Published:2009/6/24 5:41:00 Author:Jessie

C is a large capacitor that has a charge time of RSUPPLY C, assuming RSUPPLY <Rcoil, The discharge time will be Rcoil C neglecting relay coil inductance. With C = 10,000 μF and Rcoil 500 Ω, a release time constant of 5 seconds might be obtained. Many relays will hold in until the coil current decays to 25% of the pull-in current so that the actual time constant depends on the relay holding current.   (View)

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TRANSISTOR_RELAY_DRIVER

Published:2009/6/24 5:37:00 Author:Jessie

An input of 4 V or greater will drive this relay circuit.   (View)

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LATCHING_RELAY_DRIVER

Published:2009/6/24 5:37:00 Author:Jessie

An input of 4 V or greater will drive this circuit. When the relay pulls in, one pair of contacts is used to latch the relay closed. It will remain closed until S1 is pressed.   (View)

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FAST_TURN_ON_DELAYED_OFF_RELAY_CIRCUIT

Published:2009/6/24 5:41:00 Author:May

C is a large capacitor that has a charge time of RSUPPLY C, assuming RSUPPLY <Rcoil, The discharge time will be Rcoil C neglecting relay coil inductance. With C = 10,000 μF and Rcoil 500 Ω, a release time constant of 5 seconds might be obtained. Many relays will hold in until the coil current decays to 25% of the pull-in current so that the actual time constant depends on the relay holding current.   (View)

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HIGH_MPEDANCE_RELAY_DRIVER

Published:2009/6/24 5:35:00 Author:Jessie

A CMOS gate is used to drive a switching transistor and relay.   (View)

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TRANSISTOR_RELAY_DRIVER

Published:2009/6/24 5:37:00 Author:May

An input of 4 V or greater will drive this relay circuit.   (View)

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LATCHING_RELAY_DRIVER_FOR＋12_V_LOADS

Published:2009/6/24 5:33:00 Author:Jessie

A 4-V signal will cause the relay to pull in when Q1 turns on. Latching is obtained by feedback through a 4.7-kΩ resistor. A switch is used to select latching or nonlatching operation. A NO pushbutton releases the circuit.   (View)

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LATCHING_RELAY_DRIVER

Published:2009/6/24 5:37:00 Author:May

An input of 4 V or greater will drive this circuit. When the relay pulls in, one pair of contacts is used to latch the relay closed. It will remain closed until S1 is pressed.   (View)

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HIGH_MPEDANCE_RELAY_DRIVER

Published:2009/6/24 5:35:00 Author:May

A CMOS gate is used to drive a switching transistor and relay.   (View)

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LATCHING_RELAY_DRIVER_FOR＋12_V_LOADS

Published:2009/6/24 5:33:00 Author:May

A 4-V signal will cause the relay to pull in when Q1 turns on. Latching is obtained by feedback through a 4.7-kΩ resistor. A switch is used to select latching or nonlatching operation. A NO pushbutton releases the circuit.   (View)

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TWO_STAGE_TRF_REGENERATIVE_RECEIVER

Published:2009/6/24 4:51:00 Author:May

This regenerative receiver uses a tuned RE stage to improve performance. The coil in Fig. 76-24D is for the purpose of adding a second regenerative stage (RF amp). This coil is L5 in the schematic.   (View)

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SIGNAL_TRACER

Published:2009/6/24 21:13:00 Author:Jessie

This circuit uses a simple detector-audio am-plifier. The output can be connected to head-phones or another audio amplifier.   (View)

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ONE_TUBE_AM_RECEIVER

Published:2009/6/24 4:33:00 Author:May

This radio uses an untuned RF stage to boost the signal voltage up to the linear portion of the crystal diode's characteristic curve. The circuit's distortion and wide bandpass and a good-quality transformer make for a great-sounding AM radio. L1 is a winding of #22 enamelled wire 2 long on a 2 diameter plastic pipe. T1 is a tube-type radio output transformer, rated at 2000 Ω to the speaker voice coil.   (View)

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GAS_AND_SMOKE_DETECTOR

Published:2009/6/24 21:13:00 Author:Jessie

This circuit can detect smoke and a number of gases (CO, CO2, methane, coal gas and others) with a 10 ppm sensitivity. It uses a heated surface semiconductor sensor. Detection occurs when the gas concentration in-crease causes a decrease of the sensor element internal resistance. The switch in series with the SCR is used for resetting the alarm.   (View)

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CABLE_TRACER

Published:2009/6/24 21:12:00 Author:Jessie

This circuit generates a 1-kHz square wave for cable tracing. Because this circuit is simple and generates from 1.5 V, several can be used at the same time to generate multiple tones for tracing multiconductor cables.   (View)

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