I am trying to design a two stage 12v circuit on my breadboard which works like this:
- I turn on a toggle switch and 12v is supplied to two circuits (stage 1 and stage 2). When I turn the toggle switch off, I want the stage 1 circuit to turn off immediately, but the stage 2 circuit to stay live for about 2 seconds before powering off. This is to allow time for my arduino controlled circuit to save to EEPROM, then run a shutdown sequence to re-home stepper motors. The stage 1 circuit is pretty much just a signal so very low load, whereas stage 2 drives the whole Arduino board with LEDs and things, with a max load of around 2 amps.
After some research, I've come up with the following circuit:
A couple of questions:
- I'm planning to use this NPN transistor. It seems to work with 12v but it says the base to emitter is 5v - does this mean I can't drive it with a 12v signal like I have shown above?
- Is the circuit fit for purpose? It's just for test purposes at the moment to emulate a staged 12v supply I will have in my car at a later date so I'm trying to keep it as simple as possible...