Hi (Great site... I've been researching the site for a while, but this is my first post).

This is what I'm trying to do. I have a car alarm/remote starter that has a momentary pulse on one of the extra channels. What I'm trying to do is hookup this channel to the rear defroster in the car so it can be turned on via the remote. Since the output is not constant, though, I don't think it will keep the defroster on.

I found the diagram below to convert momentary to constant, but I'm not quite sure how it keeps the 2nd relay energized. I'm also confused on how to get it to turn off. I'd like it to go off when the door is opened, or when the key is inserted and the car driven away, but I'm not sure how to "cutoff" the power to the relay.

Any help would be greatly appreciated!

Thanks!

[/img]

 

You should be able to convert your pulse to a constant voltage using a flip-flop. A D type should do the trick- First pulse starts the heater and the second stops it.

If you want two different pins to turn it on and off (one for your remote and another from the opening door a Set-Reset Latch is the way to go.

Hope this Helps

-Brent

 

Use a Set reset...
Already posted it here:

http://www.electro-tech-online.com/viewtopic.php?t=3741 (4th post)

single chip can handle it

 

Meaby this!

The uper button is the trigerand the botom is the reset.

I call it " the reley filip-flop"

Attached Images

hold.gif (1.2 KB, 113 views)

 

"someone" similar...

But Your circuit can work only with "overlap" contacts, in other case work as a buzzer.

See this:

Attached Images

hold_766.gif (1.5 KB, 98 views)