This connection delay circuit allows connection delay of up to 330 seconds, using common electronic components.
DC voltage from a bridge rectifier output is maintained at 22 V by zener diode D5. Resistance R6, that enables fast discharging of decoupling capacitor C1 should have a nominal voltage of 250 V or 400 V c.c.
Timing initial is given by C4, which is loaded with C3, whose impedance at 50 Hz is about 10M, and the Half-wave rectifier D6-D7. After a certain period, the voltage on C4 is greater than 12 V potential source of T1, established by P1.
When the voltage on C4 is greater than the potential source of T1, the FET begins to conduct, resulting in conduction transition of T2. Once the relay was activated, the transistor T3 is switched into conduction by R5-C6. C4 is discharged through the transistor, so the circuit is faster returned in the initial state.