Grounding 5v or 12v

[Scarr]

Hi,
I want to have a 5v or 12v output on my car project that when grounded I can detect it and not burn anything out, I have a PIC MCU for the logic side whats the simplest way?

Thanks

 

[Nigel Goodwin]

Hi,
I want to have a 5v or 12v output on my car project that when grounded I can detect it and not burn anything out, I have a PIC MCU for the logic side whats the simplest way?

Thanks

How much current do you need to be able to draw from it?, the simplest way would be a series resistor - but it would also have the worst performance. Simple current limited voltage regulators (like the 7805) would make 1A available, but you couldn't use a 7812 for 12V (not enough input voltage).

 

[Noggin]

Umm... you mean that if your 5v or 12v line touches ground you want it to shut off? Just put a fuse on it.. or am I missing something?