It is a simple touch switch circuit, I made for our Robotics project. It will be mounted on our Robotic hand so that it can sense the touch and act accordingly. The input via the relay switch will go to the computer Parallel port, that is another topic, I hope to discuss it in another post shortly.
I used the following diagram, there is an error in the diagram actually I had to add an extra capacitor of 0.1pF between pin 2 and +ve terminal to hold the static charge from the hand and to make the circuit become stable. Otherwise the relay switches irregularly.
Here is my completed circuit:
Although the diagram shows 12 as working voltage, the circuit also works in between 5-12V.
If it is of any little use to you I will be happy.