Wednesday, June 26, 2013

Touch Switch Using 555 IC - Hobby Electronics

It's about 0455 hour here! I'm still wide awake & trying to write down something. So now a small circuit for touch switch! We all know touch switch has become very popular this days. Actually "TOUCHING" is very popular now-a-days. Seems like its 21st century's standard issue! From smartphone to desktop laptop washing machine even bath tubs have touch switches now!

So, let's dive in!

First the circuit diagram.

How will it work?

If you take a look at the datasheet of the 555 Timer IC you will be able to see #2 pin is the trigger of the IC. In this circuit it is triggered by the induced voltage of human body, the output will go high for a time determined by the 5Mohm variable Resistor & 100uF capacitor. Although it will get low after a few moments and the IC will stop providing output meaning the load will be turned off as well. A small implementation can be made to stop this from happening. The load can be anything, it can be small audio circuit, some LED lamps or a relay to drive more stuff! You can also do a lot of experiment with this circuit!

Where to use?

You can make a few for your own room maybe to turn on the light or something or for your doorbell!

Making the Touch Point:

You can use 1-2cm square thin metal sheet for the touch point.


This circuit needs some calibration. First connect everything then turn on the power supply & touch the touch point. If circuit does not work change the magnitude of the variable resistor(5Mohm) stop where it starts working.

You can also read my other writing about 555, it will make it easier to understand.

Hope it will help!

Read my other posts here!

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