Touch delay light switch circuit (6)

It is a practical touch-type delay lamp to turn on and off. The left part in the picture is the ordinary lighting circuit, and the right part is
the touch switch. Normally, the three
receivers VT1 and VT2 are
cut off, VT3 is on, and the thyristor
VT4 is off. The light E
lights up slowly. At this time, the luminous tube
LEIJ lights up to indicate the Jr off
position, which is convenient for night
use. When a human hand touches M
, the human body leakage current
divides the voltage through R and R s to turn on VT1. The 8v DC charges the capacitor C through VT1. On the same day, f passes through R and is injected into the
base of VT2 to turn on VTZ. Its collector outputs low level, VT3 is cut off, and its collector, that is,
the gate of thyristor VT4, obtains a DC trigger voltage of about 4V , VT4 is turned on, and the lamp F is powered on and emits light. After the finger
leaves M, VT1 returns to cutoff, but the charge stored in C can pass through R. Discharge to the emitter junction of wr2, "maintaining
VT2 to continue to conduct, so the light will go out for a while. Until the c charge is basically discharged, V1r 2 resumes cutoff
, VT3 conducts, and VT-I loses the trigger voltage . When the alternating current crosses zero At that time, the war was broken and the lights went out.