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Help identifying which component I need!

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450nick

New Member
Hi all!


I'm currently constructing a circuit to use in my car while I'm doing some work on the loom.This particular circuit is to be used to activate the ignition 12v supply to the rest of the car (in place of a key).

The way I would like it to work is as follows:

A momentary push to make switch is to be used to start the sequence, among other things, I need it to close two relays, one to close the main 12v loop and one small one to drive the dash lights. The problem here of course is that I need to use a momentary switch.

So my question is, what component could I use to drive the relays? It needs to take a 12v pulse from the switch, and raise its output from 0 to 12v, and then back again in the style of a flip flop circuit. I'm aware that I could do this with a microcontroller and have used them before, but I don't have any of the kit to make them up at present and am a little out of practice anyhow.

I have a similar relay in my car which controls the door lock solenoids. This flips from 12v to 0 and back again each time one of the contacts recieves an earth pulse which appears to do just what I need. The trouble is, I've no idea what its called or where to get one!

If anyone can give me a hand here, I'd be most grateful as I'm a little stuck. Ideally I'd like effectively a flip-flop relay which can have its state changed using a 12v pulse. Any ideas?

Thanks,

Nick
 

kpatz

New Member
I think that's called a latching relay.

You could do it using regular relays, a momentary button, a flip flop (555 timer or logic IC) and some kind of debouncing circuit. The flip flop would drive the relay through a transistor.
 
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450nick

New Member
Cool, would I need to adapt the R and C values as the diagram uses a 5v relay and I'd need to use a 12...
 
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