This light-controlled street lamp does not work during the day and can be automatically lit at night. It can be used in streets or rural courtyards.

        1. The working principle of the circuit
        The light control street lamp circuit is composed of a power supply circuit and a light control circuit, as shown in the figure. The power circuit is made up of power transformer T, rectifier diodes VDl-VD4 and filter capacitor C. The light control circuit is composed of photosensitive resistor RG, resistors R1, R2, variable resistor RP, electronic switch integrated circuit IC, relay K and diode VD5. The AC 220V voltage is stepped down by T, rectified by VDl-VD4 and filtered by C to provide +l2V working power for the light control circuit.

        During the day, RG is exposed to light and is in a low resistance state, so that the IC's 2 feet (strobe terminal) and 4 feet (output terminal) are both high, the internal electronic switch is in the off state, K does not pull in, and the street light EL not bright. At night, the RC is in a high-impedance state without light, the IC pin 2 becomes low, the internal electronic switch is turned on, and the EL lights up. Adjusting the resistance of RP can change the sensitivity of light control.

        2. There are two key components in the circuit. Somay-PTC is a self-recovery fuse. At the input of the transformer, the current control of the street lamp and the transformer should be controlled. The current is relatively large. The specific selection is based on the power of the street lamp. Around 800 mA.

        In addition, after passing through the transformer, there is a self-recovery fuse in the circuit. The main function is to protect the overcurrent in the circuit. When a fault occurs in the circuit and the current is too large, the self-recovery fuse becomes a high resistance state to achieve the purpose of protection.