im trying to find a wire that gets power when i turn the car off, but doesnt have power when the car is on.... i cant find ANYTHING.

im wiring up one of those scanner things and i want it to turn on when i turn the car off and i dont want to wire it to a switch.. please help.

 

i donno... you could wire up a normally closed relay to an accy. wire so when power is applied the relay opens (no flow of current) and when the car is off (no power to the relay coil) power will flow to the scanner through the battery or something...hope you understand

 

Dan is right, there is no voltage available the way the car is wired. You either have constant 12, or key on 12. You need a relay. Use a double pole relay and make sure that the relay coil is de-energized with the key off. Relay coils can draw anywhere from 50-300ma and drain the battery if the cars sits a day or two.

 

so lets say, for example, that i did wire it to a switch and could turn it on when i turn the car off, it has like 8 led lights or something.. if i left it for like 10 hours would my battery die?

 

humm I dout it alarms with LED's don't drain the battery. But it would depend on what kind of LED's you use ie how much power they are using, I guess. Anyone got a real answer? TTT

 

TTT

 

well you can wire it so when you have an alarm it turns on, and on the package it did have a way to do it without

 

Most devices will list what the average current draw is, or you can measure it if you have a multimeter. Typical car battery is around 75amp/hours. Meaning this, you can draw 75 amps for 1 hour, or 1 amp for 75 hours before the battery is considered discharged. GM specs parasitic drain for most post 95 cars at less than 12ma. An average stand alone LED figure somewhere around 5 ma, times 8= 30 ma. Not a problem. e.g., a 500 ma or half amp parasitic draw would give you roughly 150 hours, a 30ma load 5 times that. Hope this gives you some help.

 

i assume ma is milliamps. i know nothing about that kind of stuff.. the only thing i can do is wire a stereo.. ,

i guess i could just charge the battery and leave it on for a night and check the next day to see if the battery is full enough to start the car.. i have it parked for the winter so i might as well.

 

if you wanna take the easy way out just wire it into the always hot stereo wire

 

but then it will be on forever... our is there a wire that grounds when the car is off, and doesnt when the car is on..?

 

there is always a ground on the car... you are looking for a positive wire that will be on when the car is off..... there is none that I know of.... what I would do:

get a normally closed relay (current flows through the contacts in the normal position; flow is interrupted when power is applied to the coil) and wire the coil to the accessory wire (therefore turning the relay on when the car is on and turning off the light) now when the car is off current will flow through the relay to the light...pretty simple and should only take about an hours worth of work for the novice.... if you need any more help pm me

 

thanks dude

 

The wire you want to go to the relay coil is the radio wire, not the accessory one. The accessory wire is always hot, because it also powers the courtesy lights and the memory for the radio. That one I think is orange (this is according to chilton's so it may be different, but this is for 84). The radio wire is pink/blue. Run that wire to the coil on the relay. Then run one pole of the relay to the accessory wire and the other to the LED scanner. You can use the ground wire for the stereo to ground both as well.

As far as the draw, I wouldn't worry about it. I've left the LEDs in my vents on all night, as well as the undercar neons and had no problem starting it up in the morning.

 

Here is a wiring diagram, sorry for the lousy drawing. Just go to radioshack and tell them that you want a 12 volt N.C. (normally closed) SPST relay.

 

thanks! ill head over to radio shack today!

is radio shack also in the states?

 

Yes its everywhere! *runs from radio shack * AHHHHHHHHHHHHHH THEY ARE AFTER ME! lol

 

the contact (relay) in that schematic should be closed; not open in current status (no v+ to the coil)

 

if you need some relays I have tons... just pay shipping if you wanna few

 

i hate electronics. i understand nothing. but i do understand sort of what you are telling me to do i guess.

 

They will have relays that only have four contacts on them. On the back of the package there will be picture just like the ones drawn above. Two contacts are for the coil and two are for the switch. Then just connect it like in the diagrams. Radioshack even has ones that are specifically for cars that come with seperate harnesses, but those are made for a large draw device. For something like the LEDs, you can use any 12 volt relay. But if you don't feel comfortable trying to solder wires onto the contacts, then one with a seperate pre-wired harnes may be the better way to go. Why don't you just print out this thread and take it into the guys at radioshack. They should be able to help you find the right relay.

 

wow i never knew you could do that!!! and all this time i wasted cutting and pasting so i wouldnt have to print color!! THANKS!

 

:sillylol:


good luck man

 

Sounds to me like your car is from Hell

 

lol lol lol