We would like ti show you the circuit is similar to the above, but uses an N-channel MOSFET, as IRF511, 540, 640, etc. instead of the NPN transistor. Smaller MOSFETs can be used, but I do not know the part numbers. I tested the circuit with a IRF640, IRF511, IRFZ34 and REP50N06. The same circuit has three advantages, but requires only a few parts, always off to the relay and do not need a switch debounce. In operation, when the relay is deactivated, the 100uF capacitor charge up to 6 volts. When the button is pressed, is on the capacitor 6 volts at the gate MOSFET. The capacitor voltage (and gate voltage) of 6 ms should drop to 3 volts in about 200 to move enough time for relay contacts. At very slow relay, a larger capacity. With the ratification of the relay, the contacts 12 volts to the resistance produce valid 3.3K 6 volts at the gate, holding that the relay is self-sufficient. The capacitor is then discharged to zero since the relay contact 12 is connected not to the 15K resistor....