Bedside lamp safety switch circuit (3)

It is a bedside lamp safety switch composed of a thousand batteries and an optical coupler
. It can completely isolate the bedside switch from the alternating current, and the safety is very good.
  When the switch S is closed, the built-in light-emitting tube of the optical coupler A emits light, the optical coupler is turned on, and the bidirectional thyristor
VTH is controlled by R. When the trigger current is turned on, the bulb E
is energized and emits light; when S is turned on, the optocoupler is turned off, VTH
loses the trigger current, and when the alternating current crosses zero, it is turned off and
the light E is turned off. A can choose MOC940A,
M0(:3020 and other types of thyristor type optical couplers , (, which are
two AA batteries . When making,
install the circuit in the dotted box in a self-made small box, terminals a and b Connect eight
ordinary Qiming lines, lead out double-stranded plastic wires from ends c and d
to the bedside, and then connect a switch S.