TOUCH SWITCH CIRCUIT WITH 3 TRANSISTORS SCHEMATIC DIAGRAM
Here is a series of Touch Switch using only 3 transistors, this touch-based transistor switches can activate a load simply by the user touching a metal plate. It is designed to directly switch a relay to allow it to be used with large loads. As it uses only a few commonly available transistors and a 12V supply, it is ideal for hostile environments where mechanical switches would be damaged. Using a latching relay and two of these circuits, a simple two pad "touch on / touch off" arrangement can be made.
The touch pad can be most easily made by cutting a small square of PCB material and then soldering on a single wire. Alternatively, something like a penny glued to a plastic backing will do the job.
