Is there a way to make a deck hold power on startup?

rotarypower101 · 03-30-2006, 11:52 PM

Is there a way to make a standard aftermarket car deck not turn off and back on “as if power was cut from the ignition line” at startup?

I am sure there is something out there like this I just need to know what it would be called and what the process/components are.

Would a cap work for something like this?
Is there a thread someone could lead me to that talks about such a thing?

jprice02 · 03-30-2006, 11:57 PM

correct me if im wrong, but couldn't you just put a constant power to the remote wire on the back of the deck and just put a swith on it to turn it on and off yourself?

Playerbeat · 03-31-2006, 12:09 AM

yes what you want to do is hook up 12v constant power(yellow) to the Accessory wire(red one). Make sure you turn off your deck or your battery will die.

rotarypower101 · 03-31-2006, 01:27 AM

I still want it to operate in the standard way for the ignition to turn the unit on and off, but….say if you have the stereo running with the car off (acc on) and click the key over to start, the stereo would not cycle off and then back on.

I know some ignitions do not allow this as they sweep past off position from acc and then into engine crank position, but I think foreign cars (at least the ones I know of) like mine do not, and sweep from off to acc to start.

I am fairly sure this is possible, and that the problem is the drain on the system at crank, draws enough current to turn the stereo off as if power were cut.

I have mistakenly half turned over the engine and then while the engine was still in a expansion stroke but not started yet turn the key and start the engine, and this did not stop the stereo from continuing to play as it usually does at crank.

I am right to assume most if not all cars work in this way correct, where at crank if you are listening to a cd the player stops and comes back online after essentially restarting from off position?

I know my electrical system is sufficient, as I am using a newer red top optima battery with plenty excess CCA and the stereo is stock except for the HU.

Am I making this clear enough to relay what I am asking?

I just don’t want the stereo to shut off while changing the key position from acc to starting position while the engine cranks.

Playerbeat · 03-31-2006, 01:48 AM

Oh ok, yea a capacitor would work, but it would have to be a big one. You should probably go with some kind of delay circuit. Maybe something like this http://www.electronickits.com/kit/co...lec/ck1614.pdf

Wiredwrx · 03-31-2006, 02:19 AM

Quote: Originally Posted by rotarypower101

I still want it to operate in the standard way for the ignition to turn the unit on and off, but….say if you have the stereo running with the car off (acc on) and click the key over to start, the stereo would not cycle off and then back on.

I know some ignitions do not allow this as they sweep past off position from acc and then into engine crank position, but I think foreign cars (at least the ones I know of) like mine do not, and sweep from off to acc to start.

I am fairly sure this is possible, and that the problem is the drain on the system at crank, draws enough current to turn the stereo off as if power were cut.

I have mistakenly half turned over the engine and then while the engine was still in a expansion stroke but not started yet turn the key and start the engine, and this did not stop the stereo from continuing to play as it usually does at crank.

I am right to assume most if not all cars work in this way correct, where at crank if you are listening to a cd the player stops and comes back online after essentially restarting from off position?

I know my electrical system is sufficient, as I am using a newer red top optima battery with plenty excess CCA and the stereo is stock except for the HU.

Am I making this clear enough to relay what I am asking?

I just don’t want the stereo to shut off while changing the key position from acc to starting position while the engine cranks.

There is another way. What you need to do is get your voltmeter out, and check each fuse in your fuse box. Some switched fuses remain on when you start the car, and some don't. Just run a wire from the fuse that remains on to your radios acc wire, and you should be good to go.

Michael

ArcticGenes · 03-31-2006, 03:45 AM

Best route is what has been previously discussed. Connect the acc wire from the deck to the battery line then either be sure to turn the deck off. If you are worried about battery draining then get a switch.

scott_fx · 03-31-2006, 04:10 AM

Quote: Originally Posted by ArcticGenes

Best route is what has been previously discussed. Connect the acc wire from the deck to the battery line then either be sure to turn the deck off. If you are worried about battery draining then get a switch.

best route? i think wiredwrx has the best route, it doesnt involve human interaction.

another thing would be to setup a relay and delay. when the acc line hits 0volts the relay would switch to constant power for a few seconds. if the acc line doest get power in few seconds then the stereo would shut off automatically.

rotarypower101 · 03-31-2006, 12:33 PM

Quote: Originally Posted by Wiredwrx

There is another way. What you need to do is get your voltmeter out, and check each fuse in your fuse box. Some switched fuses remain on when you start the car, and some don't. Just run a wire from the fuse that remains on to your radios acc wire, and you should be good to go.

Michael

Beautiful and simple!

You really are a Jack of all trades around here aren’t you!
Thanks for taking the time to help us inexperienced guys.

Are there some unforeseen reasons why these are wired like this from the factory?

I will see if I can’t make this work for me.

Any advice as to which circuit would be best to tap into?
I should probably go with the highest rated circuit in the fuse box right?
I am taking a guess the highest rated one would have the least effect on exsisting systems right?

greenman100 · 03-31-2006, 01:01 PM

Quote: Originally Posted by rotarypower101

Beautiful and simple!

You really are a Jack of all trades around here aren’t you!
Thanks for taking the time to help us inexperienced guys.

Are there some unforeseen reasons why these are wired like this from the factory?

to give the starter the maximum output from the battery.

some stuff, like the engine computer, must stay on through cranking.

Wiredwrx · 03-31-2006, 01:16 PM

Quote: Originally Posted by greenman100

to give the starter the maximum output from the battery.

some stuff, like the engine computer, must stay on through cranking.

greenman is correct, unless you are asking why they would remain powered while cranking. Even then, he is correct. Some things the manufacturer needs or wants to stay powerd to start the car. In the past, headlights were a perfect place to grab this power, but it may not be so anymore. You could take it from the fuel pump circuit (but be carefull, if you blow the fuse, well, you stop running and lean out the engine, which could problematic). Check the door locks, they are usually a good place for switched "constant" power. You really just got to check the fuse box, it is hard to say, but please report back.

As for taking the highest rated fuse, that really isn't necessary. First, the acc wire for your stereo is most likely low power. basically, it just "flips a relay" in the stereo, and then grabs it's main power from the constant connection to the radio through the existing harness. I would be supprised if it draws more then 500ma on the acc wire. If you are worried, measure it with an AmpMeter.

Michael

lostreception · 03-31-2006, 01:41 PM

this is a really great solution i never thought of it before but the problem did bother me thanks guys

whats the easier way to make a stereo that turns off when the key is removed to stay on till the drivers door is opened?
ive always wanted that feature but could figure it out
i think i few relays would do it but i dont have any idea where to start

Wiredwrx · 03-31-2006, 01:58 PM

Quote: Originally Posted by lostreception

this is a really great solution i never thought of it before but the problem did bother me thanks guys

whats the easier way to make a stereo that turns off when the key is removed to stay on till the drivers door is opened?
ive always wanted that feature but could figure it out
i think i few relays would do it but i dont have any idea where to start

That is pretty easy as well. Will take some relays, and some wiring. If you like, when I get a chance, I will draw something up and post it. While there might be an easier way, I am sure mine will work.

Give me a little bit of time to get it done, I am at work

Michael

rotarypower101 · 03-31-2006, 03:08 PM

http://www.the12volt.com/relays/page5.asp

Radio On Until Door Opened (Retained Accessory Power)

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position.

If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory lead going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.

Wiredwrx · 04-02-2006, 06:32 PM

Quote: Originally Posted by rotarypower101

http://www.the12volt.com/relays/page5.asp

Radio On Until Door Opened (Retained Accessory Power)

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position.

If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory lead going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.

Thanks for posting that.

Michael

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