A Dozen Small Cmos Alarm Circuits

Posted on Feb 5, 2014

A Dozen Small Cmos Alarm Circuits Circuit Description This is a selection of small self-contained alarm circuits. The main features of each alarm are described on the circuit diagram itself. They all have a very low standby current. So they This is a selection of small self-contained alarm circuits. The main features of each alarm are desc

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ribed on the circuit diagram itself. They all have a very low standby current. So they are ideal for battery operation. Each pair of circuits will print out on an A4 sheet. Although they are described as alarm circuits - they will have other applications. Sw1 is drawn as either a micro-switch or a magnetic-reed contact but - so long as it does the job - you can use whatever type of switch you like. Use more than one switch if it suits your application. The output device is a "piezo" buzzer - requiring a current of about 10mA. But - you can replace it with a relay - and use the relay contacts to switch whatever device you like. Just make sure that the relay coil doesn`t draw more than about 50mA - otherwise the transistor might be overloaded.

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