AC Power Question

**one4gatr** · 06-13-2006, 11:51 AM

Brand new to these forums so be gentle. Before anyone flames me I have used the search function and read the faqs but I am still unable find my answer. I have an old HP 933mhz small form factor pc that I would like to use as my baby step. I am trying to determine how to feed the machine power though. Obviously this unit was designed for home use so it has an AC plug but unlike other desktops it has a much smaller form factor so it uses some sort of transformer/converter between the wall and the unit.

My question(s) should/can somehow convert from dc to ac and just use the existing plug or should/can I hack open the case and provide power directly to the board (and if so how). If I am just wasting my time please let me know.

Thanks for your patience.

**DarquePervert** · 06-13-2006, 11:56 AM

I suggest looking into one of the carnetix products.
They make a power supply that will very likely work with your setup using the barrel connector for power.

**one4gatr** · 06-13-2006, 04:51 PM

I guess let me rephrase the question a bit. Since I am a N00B at this please be patient. I have extensive experience with car stereo custom installs so I am cool with the hardwiring as far as the 12v. I also have tons of experience building PC's from scratch. Where I am totally clueless is how you convert the DC 12v to viable power for a 120v pc. From what I have seen carnetix and other products and it appears you just wire them directly to the board right? My experience with home PC's though you just take the leads from the power supply right to the board. So ?? is with mobile pc power supply are the pigtails already made up and just plug into the mother board? Also given I already have my box in place wouldnt it just be easier and more cost effective to go with a DC to AC converter like this pic and just "plug in" the existing AC plug? I am not sure how the carnetix power supply would work with the exisiting barrel plug on the pc I would think that I would need to go right to the MB with that setup no?

**jayearl** · 06-13-2006, 05:06 PM

The supply you are using to power up the computer right now is an AC to DC converter (I have one of these computers sitting in my office). The supply is converting wall outlet 115VAC voltage to 19VDC. This is the same voltage that many laptops use as input power.

You can use a DC-DC (12v -> 19v) converter to power up your system in the car. No need for any AC conversion.

**DarquePervert** · 06-13-2006, 05:15 PM

Originally Posted by one4gatr

I guess let me rephrase the question a bit. Since I am a N00B at this please be patient. I have extensive experience with car stereo custom installs so I am cool with the hardwiring as far as the 12v. I also have tons of experience building PC's from scratch. Where I am totally clueless is how you convert the DC 12v to viable power for a 120v pc. From what I have seen carnetix and other products and it appears you just wire them directly to the board right? My experience with home PC's though you just take the leads from the power supply right to the board. So ?? is with mobile pc power supply are the pigtails already made up and just plug into the mother board? Also given I already have my box in place wouldnt it just be easier and more cost effective to go with a DC to AC converter like this pic and just "plug in" the existing AC plug? I am not sure how the carnetix power supply would work with the exisiting barrel plug on the pc I would think that I would need to go right to the MB with that setup no?

No. The carnetix woudl replace the AC adapter for the computer. If the carnetix works for your setup (I think it will, but I'm not 100% certain), you could, in theory, take your PC out of the car, hook up the original AC adapter, keyboard, mouse, and anything else and boot it up inside, as well as outside.

The inverter convers car's DC to AC. The power brick for that computer converts AC from the wall socket to DC. You're doing a double conversion, which wastes energy and creates heat, RFI and can cause other issues as well. The DC-DC route is far more efficient, less prone to inducing noise in your audio setup and will generate less heat.

**MatrixPC** · 06-13-2006, 05:51 PM

The computer you currently have is power by something like this.
- House Wall at 120V AC -> Plug -> Transformer/Converter to 19V DC - > Pigtail to PC.
So replace it with Carnetic product (if it is capable).
- Car Battery 8-16V DC -> Carnetic Regulator to 19V DC -> Pigtail to PC.

If you use an Inverter like your last post, it will go like this.
- Car Battery 11-16V DC -> Inverter 110V -> Plug to Transformer/converter 19V DC -> Pigtail to PC.
Okay, the real problem is that when you start/crank the car, battery power is drop down to some xx Volts which may or may not cause the inverter to stop working and crash the PC if it is running.

Now you see why we recommended Carnetic product? DC to DC solution is always better. Another benefit of the Carnetic is that it has a built in Shutdown Controller which handle the on/off of the PC automatically for you.

**ODYSSEY** · 06-13-2006, 06:04 PM

Another vote for the Carnetix PSU. It will do what you need and will draw less power than and using an inverter.

You computer does not have a AC-DC power supply, like normal computers. It uses DC (19 volts) and converts all the voltages itself. You just need to convert 8-14 DC volts to 19 DC volts. No AC is involved.

Take your AC adapter to Radio Shack and tell them you need a barrel connector the same size. Then use the new barrel connector to hook it up to your Carnetix (Check polarity on the AC adapter).

**one4gatr** · 06-13-2006, 06:20 PM

Originally Posted by jayearl

The supply you are using to power up the computer right now is an AC to DC converter (I have one of these computers sitting in my office). The supply is converting wall outlet 115VAC voltage to 19VDC. This is the same voltage that many laptops use as input power.

You can use a DC-DC (12v -> 19v) converter to power up your system in the car. No need for any AC conversion.

Ahhh... I see... so presumably get the CNX-P1900 jumper to 19v pigtail barell connecter and we are all set.

Thanks for not flaming me because of my ignorance on the conversion.

So that said one more stupid question for when I decide to make my own box... I keep the same CNX-P1900 and jumper to input voltage for MB which could be 12v-whatever right? But how do you get the power to the MB? Are the pigtails self explanitory? I tried the search and just dont see alot of detail of the harness from the CNX-P1900 or equal to the MB. I do get the idea just unsure of the exact harness connections.

Thanks again.

**one4gatr** · 06-15-2006, 10:28 AM

There is a person selling a carnetix p1900 in the classifieds. Based upon my research I think this is the right unit for the job I just wanted someone to confirm my previous post as to jumper to 19v and connect pigtail to pc. Again many thanks for the help.

**one4gatr** · 06-19-2006, 09:31 AM

Thanks to all for your input. Even after reading the FAQ's I still wasnt grasping the whole power issue. For those who are dense as me I might suggest the CarNetix site.

http://www.carnetix.com/regulators/h...coose_psu.html

For some reason after reading this I finally got it.