This Panic Alarm can be used in any sudden situation of panic. It could be because of an intruder entering our house or bad health status at which we are unable to intimate to the people around us. Situations can be many for panicking. If you feel threatened or need emergency assistance, simply activate this alarm. It will catch the attention of others for immediate help.The alarm will sound for three minutes and then cease. Especially useful for women travelling alone, it is small enough to pocket or carry in a handbag.
Panic Alarm Circuit Diagram:
The circuit is simple and can be assembled on any general-purpose PCB with readily available components. Basically, it is a transistorised timer using the charging/discharging property of a capacitor to give the time delay.
When switch S1 is pressed momentarily, capacitor C1 charges to full battery voltage and provides base current to transistor T1. When voltage at the base of T1 rises, the transistor starts conducting. T1 is an emitter follower and provides charge to C2.
The circuit is in the disabled mode when the button is not pressed and hence the alarm will not function when the button is not pressed. Although the power supply will be supplied to the IC 555 all the time, the circuit will operate in the monostable mode only when the IC is enabled. The IC is in the enable mode only when pin 4 of the 555 IC is given a high voltage. This happens only when the button is pressed. The button can be made to have a plastic enclosure to have a better visibility and ease of access to it.