Free Simple Circuit Diagram
Unlike other alarm circuit that provide normally-open only or normally-closed only configuration, this alarm circuit work for both configurations. The mechanism of this alarm circuit is very simple, that the output will be active (Q1 transistor will be conducting) if IC1 or IC2 “high”. If R2 is open, then IC1 output will be high since the non-inverting input voltage will […]
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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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This timer circuit use a single op-amp which is configured as comparator, very simple, and cheap. This alarm will sound a buzzer after a period of time has elapsed since the power supply is applied. Here is the schematic diagram of the circuit: At the initial condition after the circuit is powered (you better insert a switch fro easy operation), […]
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This schematic diagram shows a water level sensor/detector/monitor circuit. An alarm is also featured in this circuit. Any fluid with a resistance under 900K between the maximum separation distance of the probes will trigger this circuit. A 4050B CMOS hex buffer is used on this circuit that is working at 5 volt supply. The 10M resistors connected between buffer input […]
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