Touch Alarm

This is a simple but interesting Project. In this circuit 555 timer is used.  555 timer ic is connected in Monostable mode.  A very high resistor is connected between Vcc and pin 7. 

When the pin 2 then it is triggered by the body because it gets a negative pulse by touching it. When touch the pin 2,  the output at pin 3 will remain High for a fixed duration. After a set duration, the output automatically goes low.

When the Touch plate is touched, which is directly connected with pin 2, then the output get High, and Transistor turns on, and an Alarm is played for some duration. After some time it will be switched off. 

Sensitivity is set by preset adjusting Any Power load can be connected by using a relay with the transistor, as shown in fig.

This circuit is more useful in doorbells, Buzzer alarms, Toy,s and some other Applications. The touch plate is made by any small surface of Metal.

The timing of output depends on the value of capacitor C1 and resistor R1. T=1.1R1 x C1

Components

NE555 IC-1

Capacitor

100uf 25v-1

0.01uf-1

Transistor

BC547-1

Resistor-

1K-1

Preset 5M or more -1

Diode

1N4007-1

OPTIONAL

Relay 12v 2A-1

Diode-1