PCB SOFT-TOUCH SWITCH
Two electrode copper-plated button acts as an RC reactive bleeder circuit connected to 2KHz 10-Volt source. With the button not touched, the FET and the transistor are off and the output is at a low logic level. When the button is pressed, its capacitance increases about five times, triggering both transistors on and giving the output a logic high. The pot can be adjusted for sensitivity.