Touch delay light switch circuit (3)

It is a relatively simple two-wire contact touch delay lamp, but the circuit operation is still very reliable. Normally
, VT1 cuts off. VT2 is turned on,
and the gate and cathode of the thyristor VT3 are
short-circuited by VT2 and turned off. The lamp F does not
light up, and the light-emitting diodes I and ED light up
to indicate the position of the switch. When a person touches
the electrode sheet M, the human body current turns
on VT1 and turns off VT2, thereby
releasing the blockade of VT3. VTS can obtain the trigger current ifif/fl through R., and the lamp F lights up. at the same
time. The charge stored in f will be quickly discharged through Vl1. After the human hand leaves J FM, VT] is cut off, and the current is
charged to (1), causing the potential at both ends of c to rise continuously. It takes about l5 minutes to make VT2 saturated and conductive.
VT3 loses the trigger current . When the AC iU crosses zero, the Qiang is cut off and the lamp F goes out. In this circuit, R. and R are all made
of high-resistance resistors, so after the alternating current is rectified by V D1~, - D4, although the output For high-voltage DC, it is not necessary to
install a voltage regulator tube on fH, and both VT1 and VT2 can operate normally.