Use PSSR to make light-controlled automatic street lights

The light-controlled automatic street light circuit made with PSSR is shown in Figure 3-59. PSSR has three driving modes: passive zero power
driving, active positive power driving and negative power driving. This circuit uses a passive zero-power drive, that is, the output terminals
5 and 6 of the PSSR are controlled by the resistance of the resistors connected to the control terminals 2 and 4. Its control characteristics are shown in Figure 3-60. When the resistance
value of pins 2 and 4 is less than the control threshold resistor (usually tens of kiloohms), the voltage drop of pins 5 and 6 is equal to the power supply voltage 220V, that is, the PSSR
is in the off state. If the resistance between pins 2 and 4 is greater than zo, the voltage drop between pins 5 and 6 is almost zero, and the PSSR is in the on state. After mastering
this feature, it is not difficult to analyze the working principle of the local circuit.
    In the figure, RG is a photoresistor. It shows low resistance when exposed to light during the day. It is only a few thousand ohms and is far less than z0. It is
near point A of the curve, so PSSR is turned off and the lamp H does not light up. When night comes quietly, the light dims and the RG resistance gradually increases
. The working point of PSSR moves from point A to point B. The BC segment is the proportional control end of PSSR. When the light continues to dim
, the working point moves from B to C, U" (that is, the voltage drop between pins 5 and 6) Gradually decreases, and the voltage across the lamp H
gradually increases, so the automatic street light also has a soft start function, which is beneficial to extending the service life of the bulb. When the sky is completely dark
, the PSSR has entered the CD segment of the curve, and the PSSR voltage drop is close to At zero volts, it is completely on, and the street light H will
emit light normally. The process of dawn is just the opposite of the above, and the street light will go out.
    The resistor R and the capacitor C form an absorption loop to protect the parameter solid state relay
PS SR .