Mini Alarm Circuit Schematic


Posted on Feb 5, 2014

This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of the person carrying the bag by means of a tiny cord. If the bag is snatched abruptly, the magnet looses its contact with the reed switch, SW1 opens, the circuit starts osc


Mini Alarm Circuit Schematic
Click here to download the full size of the above Circuit.

illating and the loudspeaker emits a loud alarm sound. A complementary transistor-pair is wired as a high efficiency oscillator, directly driving a small loudspeaker. Low part-count and 3V battery supply allow a very compact construction. If the circuit is used as anti-bag-snatching, SW1 can be replaced by a 3. 5mm mono Jack socket and the magnet by a 3. 5mm. Mono Jack plugs having its internal leads shorted. The Jack plug will be connected to the tiny cord etc.




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