Multi-point control corridor timing light circuit

(1) Introduction to circuit principle The circuit is shown in Figure 3-31. The control button switches ANI~AN4 can be installed at different locations in the corridor. As long as
any button among AN1~AN4 is pressed
, the lighting EL will light up immediately. At the same
time, it will be stepped down by the transformer, rectified and filtered, and
power will be supplied to the 555 integrated circuit. The initial voltage on
the 220tiF capacitor connected to pins ② and @ of the 555 integrated circuit is zero, so the ③ pin of the 555 integrated circuit outputs a high level, and the relay Jl actuates, causing the normally open contact Jl-l to close, and the entire circuit enters a timed self-locking state. After that, the power supply charges the capacitors on the ② and ⑥ pins of the 555 integrated circuit, and the voltage rises. When the capacitor is charged about 2/3 of the DC power supply voltage, it is the timing time, which takes about 3 minutes. At this time, the output of pin 3 of the 555 integrated circuit flips to low level, then the pin is released, the contact switch Jl-l is automatically disconnected, and the light EL extinguished. Just press any button among AN1~AN4 again, and the timer will be reset to turn on the light.     (2) Component parameter selection The selection of components is shown in Figure 3-31, and there are no special requirements.     (3) The multi-point control corridor timing light circuit is shown in Figure 3131.