Simple Touch Switch Using 555 IC

This 555 circuit will activate a buzzer and turn on a LED lamp when you touch the probe. Here is the circuit’s schematic diagram:

lf you touch the plates, the lamp and the buzzer will be activated for a predetermined time period. The time period is determined by 100k resistor and the 10uF capacitor. You can easily change the value for different period setting. Use 0.69*R*C for period approximation. Using the values shown in the schematic diagram, the activation period will be about 0.69 * 100,000 * 10e-6 = 0.69 seconds. Change the capacitor to 100uF then you’ll get about 6.9 second delay.