Relay control with MOSFET IRF511 Circuit
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.
When the button is pressed, the capacitor is zero volts to the gate of switching off the relay. There should be no problem making the button again to be the operation of relays, since the gate voltage is only about 1.8 volts when the button is pressed and the MOSFET requires approximately 3.5 volts or more are to start running. But you wait about 1 second or more between pressing a key need, capacitor time to load or unload. Two buttons are displayed, but you could have a number of more parallel to operate the relay from multiple locations