Light-controlled street light circuit using NE555 (2)

The circuit has been specially designed, and
the light switch and the power grid adopt a one-wire connection
method. It can directly replace the ordinary switch and
transform the lighting into a light-controlled automatic street light.
    The 220V alternating current is rectified by VDl-VD4
, stepped down, current limited, and stabilized.
A stable DC voltage of 6V is obtained at both ends of C
to supply power to NE555. Bai Da, RI. It shows low resistance when exposed to
natural light. When the resistance
value is less than 1/2RP, NE55j is set, ③ pin outputs high level, and the transistor VT3 is turned on. It
blocks the f J pole of the thyristor VT1 and VT2 and grounds it. VT1 and VT2 are both Turn off, the street light F does not light up. When night falls, RI,
resistance value = LF begins to rise /, when the resistance value exceeds 2 times the RP value, NE555 resets, ③ pin outputs low level, VT3
is cut off, and the trapped gates of VT1 and VT2 can obtain positive values ​​through R z Open to trigger current. Turning on VTI can make the street
lamp F energized and emit light, turning on VT? can short-circuit the resistor R, and send the forward voltage drop (about
8v) of VDi-VL)IO and VT1 directly to both ends of the capacitor C, so the NE555 can still obtain 6V DC working voltage. Adjusting the RP resistance
value can change the starting point of the light control of the circuit , so that the street lamp starts to light up under the appropriate illumination.