Free electronic circuit design and schematic diagram
A schematic diagram of simple tachometer circuit is shown below. Using only a single transistor as the active component, this tachometer would probably be the simplest one. The input of this circuit can be picked up from ignition pickup coil, or other wiring that gives ignition wave-form. This tachometer circuit works for 0 to 6,000 rpm. R3 is used for […]
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This is a relay circuit that detect the presence of sound to activate the relay. You can use this sound-controlled relay as voice operated switch, light control, toys, or any other application that can be controlled by a switch. Just replace the switch with this relay and now you have a sound-controlled device. This circuit uses a 741 operational amplifier […]
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A schematic diagram of a touch switch circuit is shown below. This circuit consist of timer, one shoot multivibrator and touch terminal. As timer, this circuit uses 555 timer which is connected to one-shot multivibrator. The touch terminal is used to trigger this circuit. The output of this circuit can be used to drive a power transistor, CMOS circuitry, hexFET […]
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The schematic diagram below show 2-phase and 3-phase motor driver circuits. This circuit can used to drive an AC motor because this circuit has an integrated power operational amplifier, built-in power-output stage and high amplification factor. The needed AC signal is produced by the op amp that is configured as oscillator. The motor is driven by the high-current that is […]
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This is an interface circuit for digital data input. This circuit consist of touch button, op-amp, diode, capacitor and resistors. Any conductor surface can be used as the touch probe, such as a machine-screw head having comparable area around 0.5-inch-square or similar area of any pattern on printed-circuit board. This circuit need a DC power supply that is produced by […]
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A battery threshold indicator circuit shown in the schematic diagram below has current regulation mechanism in driving the LED. A sufficient current should be satisfied at the minimum voltage but no excessive current when the voltage is at the highest level. Balance pin (5) is used as the reference voltage for regulating the current. This pin generate 23 mV, which […]
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This is a motor controller circuit that control the speed and direction of series-wound Motors. This circuit employs silicon controlled rectifiers (SCR) Q1-Q4, that are triggered in diagonal pairs. The switch St is used to control which pair is turned on because either coupling transformer T2 or coupling transformer T1 is connected to a pulsing circuit by this switch. Here […]
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