IC 555 used in many simple and useful circuits, every electronics hobbyist may surely tried IC 555 at least once while they learn electronics circuit making. Here the IC 555 Based Touch Alarm circuit is senses human touch and gives louder alert through buzzer.
This touch alarm circuit uses 9volt bias supply hence we can use general purpose 9volt battery for portable applications. Here Resistors R3,R4 and Capacitor C3 reacts as a Timing components, by varying R4 value we can obtain different timing output at the output pin 3. The SL100 transistor is reacts as a switch to connect buzzer with bias. Resistor R1 and capacitor C1 changes output wave shape as ramp depends on R1 resistor value the buzzer will produce different type of alarm sounds when the touch plate sense.
metal touch plate(coin)