Use NE555 to make push-button delay energy-saving lamps (3)

The circuit is shown in Figure 3-7. The left part of the dotted line in the figure is the lighting circuit, and the right part is the entire controller circuit.
    After pressing the switch SB, the negative half cycle of the 220V alternating current forms a loop with the lamp H through SB, VD1, and the lamp H lights up.
At the same time, the positive half cycle of the alternating current charges the capacitor Cl through VD2. Due to the function of the voltage regulator VDI, the voltage across CI is stabilized
at about 6.8V. This 6.8V DC voltage enables time base circuit A to operate. Since the voltage at both ends of capacitor C2 cannot change suddenly,
pin 2 of the time base integrated block is low level, the time base circuit is set, and pins 3 and 7 of the output end are both As a high level, the thyristor VS
is turned on by R3 to obtain the trigger current. After releasing the switch SB, the negative half cycle of the alternating current can
form a loop through the thyristor vs, the voltage regulator tube VD1 and the light bulb H, so the light H will not go out due to the disconnection of SR. At this time, 6.8V DC charges the capacitor C2 through Rl and R2
, causing the voltage at both ends of C2 and the potential of pin 6 of the threshold terminal of the base circuit to continue to rise. After about I.1(R1+R2)x0
, the potential of pin 6 rises to 2 /3 VDD, the time base circuit is reset, pins 3 and 7 both output low level, the thyristor VS loses the trigger
voltage, and when the alternating current crosses zero, it turns off and the light H goes out. After
    the lamp H goes out, the entire controller circuit is disconnected from the power supply and no longer consumes electricity. At this time, the charge stored in C2
is discharged to pin 7 through R2, and the diode VD3. Its function is to provide a rapid discharge path for C2 (
a path formed by VD3 and the internal resistance of the integrated block), so that the charge of C2 can be quickly discharged to prepare the delay for the next time the light is turned on.