I've tried various circuits with the result that the 2222 transistor fires up the relay instantly ... The relay coil is 46 ohms I'm using 4 AA cells for 6volt DC supply, a rectifier diode to control the flyback from the relay operation

I have a large selection of Zeners resistors and capacitors on hand, just need some values and hook ups ... Also I have several 2N2222A transistors like I have used for switching on relays directly without delays needed ...

Thanks for any working simple circuit suggestions


1 Answer 1



simulate this circuit – Schematic created using CircuitLab

The relay will activate a couple of seconds after power is applied by closing switch SW1.

Timing is controlled by C1 and R3. Increasing either will lengthen the delay, and vice versa.

D1/R1 quickly discharge C1 when power is removed, so that it gets "reset" and is ready for the next cycle. If this isn't behaviour you need, then you can remove D1 and R1 from the circuit.

I include D3 to lower relay voltage to 5.3V or so, since you implied that it is a 5V model. If the relay can tolerate 6V then D3 can be removed, and replaced by a direct connection from Q2's collector to the relay coil.

D2 is protection for Q2 from relay coil back EMF. Do not omit D2.


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