Car Headlights On Reminder

More important than environmental issue of energy saving, avoiding car battery failure when you leave the headlamp turned on overnight in the garage is possibly more important for your concern. This is a circuit of automobile lights-on reminder if you turn off the engine but forget to turn off the main lamp, this circuit will give warning when the headlights […]

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20Hz High-Pass Rumble Filter, Subsonic Blocker

This is a schematic diagram of 20-Hz high-pass rumble filter circuit.  Rumble noise could come from many sources, such as wind blow around an outdoor microphone, mechanical disturbance on phonograph, or many other possibilities. We can remove this noise by filtering the signal before the amplifier. The This circuit is designed for 20-Hz cutoff frequency and phonograph amplifier with gain […]

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Crystal Oscillator with CMOS Inverter

This is an astable multivibrator  (oscillator) circuit using CMOS inverter. This circuit uses CD4007 or MC14007. This circuit has operating frequency range of 10kHz to 10MHz.  The frequency is not determined only by the crystal, but fine tuned further by C and R that determines the exact operating frequency of this circuit. For proper operation, Pin 1 and 5 should […]

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Fast Sample-And-Hold

Sample and hold circuit is used to pick a signal and hold the level at its output, making it useful for analog digital conversion or other application where the processing need a constant level signal for the input. The circuit that is shown in the schematic diagram below is one example of fast sample and hold circuit. This sample and […]

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