Lighting light and dark conversion circuit

The light shading converter is the simplest light shading circuit. If you listen to music or watch TV at night and want to dim the lights, you can
use this light-dark conversion circuit .
    (1) Circuit principle description As shown in the figure, when switch S2 is closed, the lamp
is powered by 220V AC power and lights normally. When S2 is disconnected and Sl is closed,
it is powered by a half-wave rectified power supply. The AC power obtained by the lamp becomes smaller and the brightness of the lamp becomes darker.
    (2) The maximum reverse voltage of the component selection diode
VD must be greater than 1.5 times the effective value of the AC voltage, that is, greater than 330V. The maximum rectified current of diode VD is
determined according to the wattage of the light bulb. ioow bulbs should be 500mA, 60W bulbs should be 300mA, and 25W bulbs should be
100mA. Of course, it is entirely possible for light bulbs with small wattage to use diodes with the largest rectifying current.
    (3) The debugging circuit is shown in Figure 9-10. Generally, it can work without debugging. Open S2 and close Sl. If the lamp does not light up, it may be that
the diode is internally open. If the lamp lights normally, it may be that the diode has a breakdown and short circuit.
    If the light already has a switch, you can omit Sl and just short-circuit Sl. At this time, turn on the light switch and then close
S2. The light will light normally. If S2 is disconnected, the light will dim.