This luggage or bike alarm can be used while travelling by trains or bus and we generally lock our luggage using a chain-and-lock arrangement. But, still we are under tension, apprehending that somebody may cut the chain and steal our luggage. Here is a simple circuit to alarm you when somebody tries to cut the chain.

T1 enables supply to the sound generator chip when the base current wire (thin enameled copper wire of 30 to SWG, used for winding transformers) loop arround the chain is broken by somebody, the base of T1, which was earlier tied to positive rail, gets opened. As a result, T1 gets forward biased to extend the positive supply to the alarm circuit. In idle mode, the power consumption of the circuit is minimum and thus it can be used for hundred of travel hours.

Luggage chain alarm circuit diagram

chain alarm
To enable generation of different alarm sounds, connection to pin 1 and 6 may be made as per the table bellow.
pin selection


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