Trans AM Scotto

What kind of switch is a temporary switch? I want to be able to turn on a 12v switch inside a vehicle but then be able to turn the accessory off in the rear and have the switch reset by it self once the vehicle is shut off?

Let me know if I have to explain better.

Thanks

WhiteBird00

iTrader: (4)

I think what you're looking for is called a latching relay. Pressing a momentary push button connected to a latching relay will turn it on and it will stay on even after you release the button. It can be wired to disconnect using a separate switch mounted elsewhere and it will automatically reset whenever the power is shut off.

The rear defogger is an example of this type of setup (although it also has a timed shutoff). You press the button once and the defogger turns on and stays on even though you released the button. Press the button again and the defogger shuts off. Or, turn off the ignition and the defogger shuts off as well.

Trans AM Scotto

Yes, thank you. Do you know of any sites to help me out with this. Or even any other site with some more tricks?

WhiteBird00

iTrader: (4)

You can easily make your own latching relay using an ordinary automotive 30-amp relay and a diode.


In your case you would change the "constant power" at terminal 30 to an ignition controlled power source. That way the relay would reset when you shut off the ignition.

The way it works is that the positive pulse on terminal 85 (from your switch) trips the relay and allows current to flow from terminal 30 thru terminal 87 to your accessory. Once the relay has been tripped, a small portion of the current also flows through the diode from terminal 87 to terminal 85, keeping the relay coil energized and the relay closed. The two ways to turn the circuit off once it's tripped are to interrupt the ground for the relay coil (as shown with the separate reset switch connected to terminal 86) or interrupt the power supply going to terminal 30 (by turning of the ignition).

Trans AM Scotto

Thanks, I'll give it a try.

Trans AM Scotto

Hey, I have not tryed the relay out yet, but have two more questions

Can there be a constant 12volts going to 85 without burning up the relay or does it have to be just a pulse?

What diode should be used? How do you determine it?

Thanks Again

WhiteBird00

iTrader: (4)

Yes, you can have constant power to terminal 85 of the relay without causing any damage but it defeats the purpose of having one switch to activate and a different switch to deactivate.

You can pick up a 1-amp or 2-amp diode at Radio Shack or any electronics store. It doesn't really matter which one you use.

Trans AM Scotto

Just started to work on the relay but I don't think that it is working proper. I have 87 going to a light and going to a ground. 30 has a constant 12v. 85 has 12v momentary and 86 has momentary.

The only way the light works is if I hold down the ground momentary and then press the one on 85 in. When 86 ground is release it goes out.

Is this correct or is it not working properly?

Maybe it would be easier to say, what do I have to do to have a 12v acc. be turned on and off by a 12v pulse. This way I can just run 2 12v momentary switch. Is this possible?

WhiteBird00

iTrader: (4)

You've got it almost right. The momentary switch at terminal 86 has to be normally closed (current must flow when the switch isn't pressed). The object is to have constant ground on 86 so that the power can run from 85 through the relay coil out 86 to ground - this is what keeps the circuit running. Then when you press the switch on 86, it opens the circuit, interrupts the ground, and turns off the relay.

Trans AM Scotto

Ok, so I just need to get a momentary that stays closed, for the ground side. Think I can manage that.

What about the have the accessory turned on and off by the same 12volt pulse.

Do you know of any site that I can read up on some 12volt stuff. I have been to the the12volt.com, but that is mainly audio and alarms.

Thanks again

WhiteBird00

iTrader: (4)

No, you can't have a latching relay turn off using the same momentary switch that provides the 12V pulse to start it. Once the relay is latched it is receiving power through the diode to keep it active so adding another power pulse won't affect anything.

It would be helpful if you could give some more details about what you're trying to connect. For example, it might be possible to wire a two-way momentary switch (like a factory convertible top switch) to both activate and deactivate the circuit depending on which way you press it. Or maybe using a standard switch instead of a momentary one might be an answer. It is possible to wire two standard switches to independently control a circuit (like household lights that have a switch at each end of a hall).

AGray89

iTrader: (5)

whoa, i was just thinkin about the same thing... and it sounds kinda like the same scenario, so lets see if we can combine thoughts to find an answer....

ok, i have my 12v pulse from my door locks that flash some neon lights i have on my car... i have it all set up through 2 relays so that if i switch on the lights manually, the pulse doesnt affect anything, and also when i have the car on the pusle doesnt do anything... so now, instead of them just flashing, i want to be able to turn them on and off with my remote (12v pulse door locks) sooo... how would i go about doing that? I need to get some sort of electronically controlled switch that will turn on when a pulse is sent through it, then when another pulse is sent through i want it to switch off... any ideas??

AGray89

iTrader: (5)

eww i fried a wire... hmm, now i have to figure out the problem... i used that latching relay, im going to take everything apart and make sure i have that set up right... and then i have a regular relay on the ground which is supposed to break the ground when a pulse is sent through it... is there anything i should know otherwise? cuz i cant figure out what the problem is...