One of the street light control circuits

The street light control circuit can control the street lights to automatically turn on at dusk and turn off at dawn. Due to the high power of street lights, they are usually
controlled through relays and contactors.
(1) One of the street light control circuits.
    Figure 2 90 is the simplest lighting light control switch circuit, which can be used for automatic control of electric lights in the hospital, and is more suitable for
automatic control of ship mast lights. This circuit has no anti-flash and light-shielding interference capabilities.
    This circuit uses the phototransistor VTi as the detection element, and
consists of VTa and VT4 to form a Schmitt circuit, which has reliable operation. During the day, when
the phototransistor VTi is exposed to light, the internal resistance is very small, the relay KA is released, and
the street light EL goes out. At night, the internal resistance of VTi becomes larger, KA pulls in, and the street
light EL lights up.