Number of thefts and robbery has increased to a greater extent. Unemployment, poverty might have been the cause for this but still stealing others property is a serious crime. The only way to stop this is by alerting people themselves with proper security arrangements. Bus hijacking is what we heard commonly of, this is where the fear of crime lies. We have seen people stepping ahead for protection, they use chains, lock as security arrangements to secure their luggage. This might be a nice try, but still is not sufficient to reassure ourselves that we are in safe hands, our property is in safe zone. Locks and chain can be easily broken and our attempt for safety goes in vain. And, therefore to reassure ourselves here we have presented a simple alarm circuit to alert us from such situation when somebody tries to cut the chain.
The circuit construction of luggage security system is so simple. It uses a single IC, three transistors, three resistors, a switch, a speaker and battery. The sound generator chip gets activated by the supply from transistor T1 when the base current starts flowing through it. From the figure, we see a wire loop is tied around the chain which is used for winding transformers. This loop constitutes a thin enameled copper wire of 30 to 40 SWG. As someone makes an attempts to break this chain and succeeds in doing so, the base of transistor , which was earlier tied to positive rail, gets opened. This compel transistor T1 to get forward biased, the positive supply is then extended to the alarm circuit. and, finally the speaker sounds warning the person what’s going on in the vicinity.
This circuit provides an extra benefit with a fact that it can be used for hundreds of travel hours. Because, in idle mode of the circuit, the total power consumption is minimum. In addition to this, this circuit provides multiple sound effects for generation of varieties of alarm sounds. For this purpose, connection of pin 1 and pin 6 of the IC1 (UM3561) has to be made following the guidelines from the table.