Electrical appliance cycle on/off timer circuit diagram

The electric appliance start-stop cycle timer circuit is shown in the figure below. The LM555 time base integrated circuit forms a multivibrator with an adjustable duty cycle. KH1, W1, KH2, and W2 are connected in series to the charge and discharge circuit of C3 to serve as the electric appliance on and off respectively. Coarse and fine adjustment of stop time. When the circuit starts to work, the power supply charges C3 through the series resistors of R3 and HK1 and W1 and V2. Pin 3 of the IC outputs a high level, the LED lights up, the relay J is closed, and its contacts are connected to the load. When the voltage on C3 rises to 2/3 of the supply voltage, the IC flips over and the relay releases. At the same time, C3 is discharged to ground through the resistor W2 connected in series on V3, R4, HK2 and pin 7 of the IC. When the C3 voltage drops to 1/3 of the supply voltage, the IC flips over and the relay closes. Work in this cycle. Each gear of HK1 and HK2 can increase or decrease the delay by 4.5 minutes, and the adjustment range of W1 and W2 is about 0~5 minutes.
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