Just touch sensitive element and actuates an electronic device that includes an alarm or actuating mechanism.
The sensing element AN1 - plated plate is connected through resistor R2 to the grid of thyratron MTH-90 (Fig. 1). The potential appearing on the grid of the thyratron when you touch the plate, sets fire to it. The arising in the chain MTX-90 pulses through the capacitor C2 is deposited on the SCR FS and include the load (relay, lamp, siren, etc.). The scheme is powered directly from the mains alternating current. The capacitor C1 performs the role of the quenching resistor. The second device (Fig. 2) convenient to use for inclusion of residential call. This scheme is powered by direct current. Half-wave rectifier is formed on the diode DZ, the capacitor C1 serves as a filter. Resistor R3 limits the current in the RL circuit, D1.
Instead of SCR COA you can use any other pick it up as follows. In series with the SCR to the network 220 includes an incandescent lamp with a power of 25 watts. If the lamp is not lit, this SCR is suitable for circuit of relay "touch". Zener COP 630 can be replaced by COP A. Resistors - MLT, mon. Capacitors - MBM 300 V.
Author: A. Sirotenko, Perm; Publication: N. Bolshakov, rf.atnn.ru