Automatic LED billboard decorative light circuit at night

Automatic LED billboard decorative light circuit at night

Shown is the automatic LED billboard decorative light circuit at night. Photoresistor RG is used to sense light intensity.
    After the AC 220 V voltage is stepped down, rectified, stabilized and filtered, a DC voltage of about 7.5 V is output to power the components in the circuit . At the same time,
the bridge rectifier stack VDO and the current limiting resistor Rz drive the two-pin tube group VD to emit light.
    When the light intensity is high, the photoresistor RG is in a low resistance state, VT1 is in a cut-off state, VT2 cannot be turned on,
there is no voltage at both ends of the capacitor c3, and the diode group VD does not emit light; when the light intensity is weak at night, the photoresistor The resistance value of emitter RG increases. When it rises to
the set resistance value, the base of VT1 obtains a voltage value sufficient to turn it on, and its emitter outputs the trigger voltage to turn on VT2, and the light-emitting
diode group VD is turned on. Light up.