Anyway to integrate this feature?

Topic: Anyway to integrate this feature? (Read 4218 times) previous topic - next topic

Anyway to integrate this feature?

December 19, 2014, 08:28:50 PM

I'm just wondering if anybody here knows how to integrate a feature that gm cars have?
My wifes cars stereo stays on even if you turn the car off until you open the door and I love it

I know the car just needs to keep supplying power to the ignition wire on the actual stereo until it's signaled to stop
I'm majoring in electrical engineering so it's definitely something I can handle I just need to know how to go about it?

Anyway to integrate this feature?

Reply #1 – December 19, 2014, 09:44:59 PM

Not sure exactly how to do it, but would start with the wiring diagram of the radio circuit on the gm car in question. I believe they have some sort of retained power system that gets deactivated with the door switch. Might be as simple as a relay with the ground hooked up to a door switch.

Anyway to integrate this feature?

Reply #2 – December 20, 2014, 12:53:03 AM

Yep, it's called Retained Accessory Power, I had a 1997 Taurus where you could still use the windows after the car was shut off.

Anyway to integrate this feature?

Reply #3 – December 20, 2014, 01:07:56 AM

Did this start in '97, for the most part?

Anyway to integrate this feature?

Reply #4 – December 20, 2014, 02:24:31 AM

Probably 1996, I could also unlock all four doors by turning the key twice :-)

Anyway to integrate this feature?

Reply #5 – December 20, 2014, 04:18:49 AM

Awww man I think I found out how lol

Thanks White85GS I probably couldn't have found it without the proper name
Looks like all it'll take is 3 relays, some diodes, and some wire
There's 2 versions too, one for negative and one for positive door triggers

Btw this is THE website for car stereo and alarm diagrams
http://www.the12volt.com/relays/relaydiagram31.html

Anyway to integrate this feature?

Reply #6 – December 20, 2014, 09:23:37 AM

the far simplest way is to do an RC time constant feed to a relay coil.

T=R*C

the relay will come to you free from stuff you probably have

I recommend a variable resistor and capacitor.
dial them in, test them on the relay and a light bulb on the contact side and verify.
something along the lines of an 800kohm resistor and 500uf cap will get you a few minutes of radio power.

now its time to cancel the radio out because your getting out of the car but the radio is still on, add another door contact switch to the relay ,,, and perhaps a quad nand gate in the mix. you have various places to obtain 5v in your car.

Anyway to integrate this feature?

Reply #7 – December 20, 2014, 09:39:44 AM

You know that's what I thought about first since all I really wanted was for the stereo to stay on until I crank the key back to acc power

Definitely looking into it thanks

Btw wouldn't a 500uf cap be pretty big?

Anyway to integrate this feature?

Reply #8 – December 20, 2014, 01:19:10 PM

The EEC power relay has a delayed drop out. If you listen closely in the center of the dash, you can hear it click about 4 or 5 seconds after you shut the car off. If you have ever pulled codes with an buttstuffog meter you can see the delay when you turn the key off.
I expect this is so the EEC program can go through a shutdown procedure before power drops.
I don't see anything the wiring diagram external to the relay to cause the delay.
I am guessing (because I don't know for sure) that the delay is built in the relay.
A relay like this would give you the delay you need to bridge the ignition switch gap between Run And Accy.

Anyway to integrate this feature?

Reply #9 – December 20, 2014, 04:07:46 PM

I built an accessory delay for mine. I used a 555 timer, a couple relays, and some miscellaneous caps, resistors and diodes. I have a thread about it here someplace. Mine sits in a project box behind my dash on the passenger side.

Anyway to integrate this feature?

Reply #10 – December 20, 2014, 04:11:28 PM

Just a thought. For what reason would you want this fore. I know the new cars and trucks do it that way but WHY, In my view there is no logical reason for it. Just sayiong

Anyway to integrate this feature?

Reply #11 – December 20, 2014, 05:14:52 PM

Because it's better than OnStar?

Anyway to integrate this feature?

Reply #12 – December 20, 2014, 08:32:55 PM

i don't get it either, but the window thing, that makes sense.

Anyway to integrate this feature?

Reply #13 – December 20, 2014, 10:38:42 PM

I like it because it reduces the amount of battery you are using

in our cars If you want to play your radio, you have the turn the key forward or backward,,, that energizes several unrelated fused / unfused devices that you don't really care at that moment to power.

I see how it makes sense.

Foe is right he did up a project box but like each person, they build it how they want.

As for a capacitor in size is concerned,, you can change the value of the resistor and decrease the capacitor,,
you could easily score the parts you need out of an old PC power supply or anything electronics ,,,, makes it a green project.

Anyway to integrate this feature?

Reply #14 – December 20, 2014, 10:56:08 PM

Idk it's just ones of those features that I've come to love
It has just been so handy and convenient in my wife's car that I want it on mine
Stereo staying on, Windows still function, and I'll probably even try to keep the trunk open circuit on
I hate having to stick my key back in just to open the trunk or gas door
It's more than enough for to get it working plus I don't see it as work, it's fun for me honestly