In today’s electronic equipment is widely used touch control. Option sensor available for beginners repetition hams, offers Czech magazine “Amaterske Radio”.
If you touch the plate, induced in the human body room electrical AC voltage increases two-stage ULF transistors V1, V2, and then straightens diode VЗ. Direct voltage of about 4 V, which appears at the sensor output, is the command signal.
The device used any low-power silicon transistors, for example, КТ342, KT315 with any alphabetic index. Diode any silicon (Д220, Д219). Capacitor — KBG-And or BMT. Touch plate — cut foil fiberglass with a size of 20X20 mm.