Schematic diagram of thyristor electronic time relay

Photocoupler

The figure is a time relay circuit composed of a unidirectional thyristor, which is mainly composed of a DC power supply, a delay trigger circuit and a main circuit.

The 220V grid voltage is outputted with a DC voltage of about 15V after T-buck, VD2 rectification, C2 filtering, and VDl regulation.

When the power is turned on, the DC voltage is charged to C1 through R1 and RP. After a certain delay time, the voltage on C1 reaches the peak voltage to turn on the single junction transistor VT, and the pulse voltage formed on R3 triggers the thyristor VS. Through, the relay K is electrically connected and its contacts act.

The time from the power-on to the contact action is the delay time of the time relay, and its length can be adjusted by the potentiometer RP.

After K is powered, its normally open contact is closed, shorting capacitor C1 and discharging it quickly, ready for the next charging delay; in addition, the contact of relay K can control the delay action of electrical equipment.