Hey everyone

Welcome back to my Blog today, I am making a touch switch which is use to turn on the computer by touch of your finger just like smart phone. Let’s make it. Every computer has a power button which turn on computer, the button comes with CPU case it’s a physical type which we have to press until its contact pin connected to each other. Its look like old school, then I thought that can I make the computer on by just touch of my finger. After thinking about it I find a solution for it which is simple and easy to make and it’s don’t require any microcontroller.

Step 1: Component

1)Touch sensor X 1

2)Opto-coupler X 1

3)Resistor 270ohms X 1

And some basic tools and wire (old USB for powering and a female connector)

Step 2: Working

I am using simple touch sensor which is named as TTP223(fig 1) which is really chip in price and perfume well as per my requirement and it is small in size

To turn on the computer this terminal 5and 6 is need to sorted which is done by power button(Fig2 and Fig 3).

The sensor cannot directly connect to the pc because its work on 5 v and we cannot drive current through the power button of the PC for isolating both the side simply I am using an optocoupler.

Optocoupler(Fig 4) is device which optically isolate two side of circuit, as in name its uses light to activate transistor as shown in figure. I am using 4n35 optocoupler as I am having it but any optocoupler is usable as its job is only connect two terminals when its on

Step 3: Circuit Diagram

I made all the connection as per in the circuit Diagram it required 5v for that I attached USB cable by which it can power directly by computer or a 5v adapter.
As show in figure I attached the one side of optocoupler to the touch sensor. Whenever I touch the sensor, it turns on the optocoupler which result in sorting the terminal 5 and 4(). As it is activating by light there is no physical connection between two of the side which is most required in this project

At the end its is easy to make and look cool but it has some down side if you touch it by mistake it will turn on or turn of your computer.