"Dumb" Power Supply with 12V and 5V Output

**Caelric** · 01-23-2006, 09:32 PM

Looking for a small power supply, to provide a solid regulated 12V to run my Xenarc screen, and a regulated 5V for a DVD burner and a powered USB hub. Obviously doesn't need to be high output, but I want it to survive battery cranking. And, by "dumb" in the title, I don't want a shutdown sequence, or anything like that; it will take it's shutdown cue from the main power supply (a DSX12VD) which provides a good ACC line,t hat will turn off when the computer turns off.

The reason I am not going with a 12V POL is because they all state that input voltage must be 1-2V higher than the desired output voltage. So, when the engine is not running in my car, the battery voltage is about 12.5 or so, and I would like to have a solid 12 volts to my Xenarc, in order to maintain image stability and display life, rather than subjecting it to a flucuating voltage

I think the Carnetix CNX-P1290 will do the trick, is there anything I am missing?

Dave

**JjSwee** · 01-24-2006, 12:31 AM

I was looking for something for a powered USB hub, and while I was looking at hubs I noticed it requires 7.5Volts. Just a heads up.

While I'm at it, anyone able to link me to a schematic to make a 7.5volt supply?

**Caelric** · 01-24-2006, 12:35 AM

Thanks, but the specific hubs I have all require 5 V. I was sure to check that when I bought them (actually, before I bought them, 5V or 12V was a requirement, nothing in between)

**DarquePervert** · 01-24-2006, 07:22 AM

Originally Posted by Caelric

I think the Carnetix CNX-P1290 will do the trick, is there anything I am missing?

It will do what you need.

**MatrixPC** · 01-24-2006, 10:18 AM

**thwang99** · 01-31-2006, 04:31 AM

Originally Posted by DarquePervert

It will do what you need.

Have a question about the carnetix, will it allow the computer (notebook carpc I am using) to remain on when you turn off the car?

- Tony

**Ladzio** · 01-31-2006, 09:19 AM

Same questions here. I am considering getting carnetix p1260 just to have stable 12V for my Tview, which needs 10W only though (would love a cheaper solution if possible), but how do you supply 12V with car not running?

Thanks a lot in advance!

P.S. Read a little more here and there, looks like Carnetix is way to go, since it can take 7.5VDC and ive out still 12V when engine is off.

**DarquePervert** · 01-31-2006, 03:55 PM

Originally Posted by Ladzio

Same questions here. I am considering getting carnetix p1260 just to have stable 12V for my Tview, which needs 10W only though (would love a cheaper solution if possible), but how do you supply 12V with car not running?

The battery.

**Ladzio** · 01-31-2006, 04:31 PM

Originally Posted by DarquePervert

The battery.

I incorrectly fraised(sp?) my question, I believe. I read carnetix specs and there is a wire than needs to be hooked up to some power source that goes on or off with ignition. When, I said with engine not running, I meant to say keys out of ignition. Therefore, I believe I would need to hook that wire to some constant 12V or just keep keys in with IGN on. As well as get voltage regulator to keep an eye on the battery charge.

**Wiredwrx** · 01-31-2006, 04:52 PM

Originally Posted by JjSwee

I was looking for something for a powered USB hub, and while I was looking at hubs I noticed it requires 7.5Volts. Just a heads up.

While I'm at it, anyone able to link me to a schematic to make a 7.5volt supply?

Sure, try an LM338K http://www.national.com/ds/LM/LM138.pdf

Michael