Light-controlled street light circuit using NE555 (1)

A light-controlled automatic street light composed of NE055 inch-based circuits. It has
the characteristics of small size, low cost, no contacts, good anti-interference performance and low body power consumption. It can be used not only for incandescent bulb screwing, but also
for high-pressure sodium lamp control.
    NF, 1 5 5 are connected as a Schmitt trigger. During the day, the natural light is strong, the photoresistor RIL shows low
resistance , the ② and ⑥ pins of the time base circuit are island level, the main stem is 2/3Vm, and is in reset. state. Its output terminal ③
pin inputs low level, the thyristors Vl and H
are turned off without trigger current, and the street light E
does not light up. At night, R1 loses light and becomes high resistance, causing the trigger terminal ②
of the time base circuit to be at low level (less than i, 73¨D), which is called the base circuit Xuan position, and the output terminal ③ pin jumps to high level, VT The trigger current is obtained from R and turned on, and the street lamp E is energized and emits light.   R,, (,, form a interference pulse absorption circuit to prevent short-term light (such as lightning flash, vehicle light, etc.) from interfering with the normal operation of the circuit. Since the Schmitt trigger composed of a time base circuit has /3Vrm hysteresis voltage, thus preventing street lights from flashing when the circuit is in a critical state. The varistor RV connected in parallel to VTH can absorb various peak interference pulses in the power grid to protect the thyristor VTH from overvoltage and damage. If     this circuit is used to control incandescent lamps below 10ow and 100ow, VTH can use 1A/600V small sealed bidirectional thyristor, such as MAC97A6 type, etc. If used to control high-pressure sodium lamps, VTH can use BT137 (BA/600V), T0805 ( SA/500V) type and other bidirectional thyristors require a minimum gate trigger current of iOmA, and a sufficient aluminum heat sink should be installed. The RV uses MY (;471 type zinc oxide varistor , requiring a peak current of ≥100A .See the figure for other device requirements.