Plastic sealing machine circuit diagram

When K1 is just turned on, KZ is powered on and works. Since the voltage of C2 is very low, BG is not conducting and the relay is energized. When C2 is charged to a certain level, BG is conducting, SCR is conducting, the relay power-off contact is disconnected, and heating stops. After K1 is disconnected, the power on C2 is discharged through D2, and the next cycle is ready. Adjusting W can change the working time of the sealing machine. In order to improve the reliability of the circuit, D3 increases the BG emitter voltage.