Lighting lamp power outage self-locking switch circuit

For lighting controlled by a pull-wire switch, if there is a power outage, it is difficult to distinguish whether it is "on" or "off"
. When the power comes back at night, it will often cause lighting all night and waste electricity. If the circuit shown in Figure 19 is used instead Ordinary
pull-wire switches do not have this shortcoming. When the power is restored after a power outage, the circuit will lock itself and the light will not be turned on.
    SB1 is the light-on button. Press SB1, the thyristor
VTH round door plate will receive the trigger current lni and turn on, and the light F will be turned on.
Lights up. Although the J trigger circuit is disconnected after the orange hand,
after the thyristor is turned on, there is a leakage current between the first anode and the gate, so
the capacitor c has a charge and discharge current, and this charge and discharge current serves as
the gate of VTH The current keeps WrH in the buzzing state
, so the lamp E is still on. When you need to turn off the light, just press
the ISB2 button to turn off the light. Because S1 connects the gate of VTH to
the second anode, VTH is lost. The trigger current
will turn off when the AC crosses zero, and the state E will go out. At the same time, the charge stored in the capacitor C will
be discharged If the AC box is restored after a power outage, because VTH is in the off state, capacitor (no discharge current is allowed to run out.
VTH will not be triggered to conduct, thus realizing self-locking after power outage. Unless SB1 is pressed again, the lamp F will be
lit again.
    VTH should depend on the power of the lighting lamp . Generally, When brushing the HCR3AM small plastic-sealed thyristor (3Aj
600V), with a small heat sink, the load power (referring to the power of the lamp E) can reach 100W. If
the power of the lamp E is greater than 100W, the VTH should be installed with aluminum Open hot plate. Use RJ-1W metal film resistor for R. (
It is best to use oil-immersed paper or acrylic resistor with a voltage of 400V.