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Relax 1st July 2006 05:46 AM

In Home Car Audio
Hello Everyone Once Again!

I am on a new quest to put a Car Head Unit in a computer for looks and for coolness. So, I was wondering if it is possible to rig up a computer power supply, which can do up to 34 amps at +12V.

I have no doubt I could hook up the deck to the power supply and it would be able to run it, I am just unsure of how to hook up certain things.

1. How do I connect the PS turn on lead? On the majority of power supplies, the power supply doesn't turn fully on until the computer power switch is turned on, problem is why? I think the switch completes the circuit from the PS On to ground, and once the current flow is sensed, the PS turns fully on.

2. What is the best way to connect the ignition, or turn on lead of the amp? I was thinking a simple switch from the PS +12v to the Deck's ignition wire. Once flipped, the deck would get some voltage, and turn on completely.

3. If my thinking above is correct, where should all the grounds be connected? A CP PS has several grounds that come out of it. SHould I connect them all together to one point? Or are they all connected inside the PS already?

Basically I was guessing at this to work:

Flip the two switches, and whammo it all lights up and plays some tunes.

Also, what do you think of this supply to run a deck (10 Amps Max) and a small amp (20 Amps Max)?
Thanks for taking the time to read this and perhaps help me out!

Have a good one!

30bandgeek 2nd July 2006 06:49 AM

put small 12v battery in parallel

Relax 2nd July 2006 05:56 PM

In parralel with what? I do not think I could use the Computer power supply to charge the battery, and I am sure the Computer PS's DC is as good as a Car's.

I just need help figuring out the best way to turn things on and connect the main power.

phreeky82 2nd July 2006 11:51 PM

In the ATX power supplies the motherboard tells the PSU to turn on/off, any switch on the case just runs to a header on the motherboard, so that physical switch is useless (it's a momentary switch).

the big problem is that you actually need some constant power to the head unit so it keeps its memory, but the PSU wont supply any power constantly - and you can't just use a small plug pack or similar to give it constant power because that same wire from the head unit is also the one which draws the big power when it's on - the ignition wire for the head unit is just a switching wire.

hence i guess something like the battery in parallel with the supply voltage was suggested - provide sufficient power for memory when it's turned off, and have both the power and iginition wire connected to +12v of the PSU.

whether the battery thing works i'm not sure, problems i can forsee is how the battery will deal with "copping" the PSU voltage, and whether the PSU grounds the +12v line when it's turned off.

firefart_1st 3rd July 2006 12:29 AM

ican say that there are computer PSU capable of 2 times 18A continous on 12V.
650W cooler master psu
and there are more brands out there... find one that suits your needs on power.
one more thing is.

the psu's available today have an output of 12V 2A (SB)
when the pc is in stand by it uzes that.
if the head unit has an separate output try to connect it that way.

i hope you understand this ^^

firefart_1st 3rd July 2006 12:34 AM

this one has 29A on the 12V out and only has one.
ultra 600W ATX Power Supply ( ULT31638 )
search on google :P:smash:
the battery on paralel is good for the voltage drop when deep bass comes up. and when these PSU's arent pushing power from 3.3V and 5V they dont make much heat.
i uzed 2. one is fanless. the other it with a smal fan and on low voltage i'm taking 8A continous from the second one. it does not heat much...

Relax 3rd July 2006 12:44 AM

well, i learned several things. First off, the ATX pinout allows for a simple switch from PS-ON to ground to turn the supply on and off, so in that regards my plan is correct.

The closest voltage to 12 + for a constant is the 5 volt VSB. Will this be sufficient to maintain the memory of the deck? If not, perhaps a voltage doubling circuit or an op amp would allow me to ramp it up to 12 volt?

I tested shorting the PS On to ground, and it does indeed turn the power supply on till it is disconnected.

As far as amperes, the power supply I posted is of lower quality, but will give out 34 amps at 12v. I think for these purposes, it will be sufficient. If it isn't, It is not that big of a loss anyways. Same thing if the power supply craps out on me.

So only problem I have now is finding a way to maintain the HU's memory when the PS is turned off.

Here is the pinout of ATX12V power supplies:


firefart_1st 3rd July 2006 12:52 AM


my mistake... its nos 12V SB but 5V SB. :xeye:

but you have to worry about how much miliamperes does the HU takes for the memory.

5V wont do it. might even take to problems...

Relax 3rd July 2006 02:15 AM

well, the power supply in the first post has a 5volt SB, and can draw 2 amps, so I believe it would be fine if we could somehow up the voltage. Perhaps there is a small component number way to do it?

phreeky82 3rd July 2006 06:31 AM

like i said earlier though not only must you get 12v constant (so lets assume you solve that issue), this power feed must also be the primary power supply for the head unit.

a reasonable size cap just before the head unit and switching via a relay when powered on might be fine to solve that issue (cap to give a solid supply of power for the split second the relay flicks, if it's even needed at all)

also take into a account that car audio components like head units deal very well with varying voltages, probably fine anywhere from 10v to 15v

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