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L21, Simple Touch Sensitive Switch Circuit

We all know about a little chip 555 Timer, like as a small microcontroller of without programming. The following circuit is no exception, it's a sensitive touch switch circuit using the IC 555.

Here the IC is configured as a Monostable multi-vibrator, in this mode the IC activates its output when it’s get a logic high in response to a trigger at its input pin 2. The activation time period of the output depends on the value of C1 and the setting of VR1.

When the touch switch is touched pin 2 is pulled to a lower logic potential which may be less than 1/3 of VCC. This instantly reverts the output situation from low to high activating the connected relay driver stage.

This in turn switches ON the load attached with the relay contacts but only for the time until C1 gets fully discharged.

You can place any LED with series resistor of 1K replace to relay.


  • 555 Timer IC

  • Transistor SL100 or BC107

  • Diode 1N4007

  • 12volt relay

  • VR1 = 5Mega ohm, R2 = 10 ohm, R3 = 1k

  • C1 = 100uf, C2 = 0.01uf (microfarad)

  • 12volt battery

  • Touch plate you can design yourself by a metal plate

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