Car power supply for an Atx

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Old 03-10-05, 04:40 PM
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Car power supply for an Atx

I need to build a power supply that will power an atx computer in the truck. I need at least 200 watts. Can anyone help me with that or show me where to get one for real inexpensive.
 
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Old 03-10-05, 06:03 PM
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You can buy a 200 watt inverter for $32.

http://www.donrowe.com/inverters/150_800_watt.html
 
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Old 03-11-05, 04:32 AM
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You can buy larger inverters also. I have a 300 watt model. It cost me about $15.00 after a rebate.

Just don't run this with the engine off, at least not for very long, or you will be looking for a jump.
 
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Old 03-11-05, 04:49 PM
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Hello all,
Thankyou for your response,
However I have some concerns.

1st. The power supplys for computers that I have seen say they take 115v @ 5 amps. According to ohms law the amount of power would be 575 watts.

2cd. If I use an inverter then I will be incredibly unefficnet.
I mean step 12vdc to 115ac then back down to 12v and the other voltages required.

Also I already have an auxillary battery complete with a battery isolator. which means my main battery will never be touched by anything left running after the engine is off. When the alternator is running it will recharge both batteries at the same time.


I understand that I could use an Inverter However, I am looking for the more effiecinet alternative. I am willing to build almost any complexity of a circuit just simply becuase I enjoy it. I would appreciate any help in that area, in terms of a website with circuits or something of that nature.

Thankyou,
Robert
 
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Old 03-11-05, 05:02 PM
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Then you need to take 12 volts and convert it to +12VDC -12VDC and 5VDC. The +12 an + 5 will be easy with voltage regulators. The -12 will not be so easy.
 
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Old 03-13-05, 09:08 AM
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As a former field rep, I can tell you I ran a 500W inverter to power both my laptop and printer. If you check the specs on the inverter most of these mid level inverters will handle a "start-up" spike to about 1100W. I never had any issues with the one I had. You can also buy a 750W inverter or one over a 1000W if you think you have need for that much juice. A word of caution as to quality, I've seen some of the 12V lighter adapters melted off some inverters that other field reps purchased so with higher load you may want to make note of how to supply the 12V feed. I'm not going to claim to be an expert such as the moderators but I wouldn't hesitate to mount an inverter permanently and wire it to the second battery.
 
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Old 03-14-05, 05:18 AM
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If you only require 200 Watts, why are you worried about the current draw of the power supply? 5 amps is probably a maximum. The only computers that I've seen that would ever use 575 Watts are frankensteinian machines built by tech-heads. Just a guess, but I would say that most modern machines (except for super high end stuff) probably never use more than 300 Watts. Just because a PSU is rated at a certain wattage, that's never really true figure of what the computer uses.

If you're worried about your rail voltages (+5, -5, +12, etc.) being off because of uneven power, there are many PSUs that have active power factor correction (PFC) that clean up the voltage to give you more stable rails. You could also buy an external line conditioner to do the job.
 
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Old 03-16-05, 09:25 AM
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Buy yourself a watt meter, like the Kill-A-Watt, and find out exactly how much power you need.

I guarantee you don't need anywhere near 575 watts.

I've got:
P4 laptop
Creative 4.1 speakers
cordless phone/answering machine
network printer/fax/copier/scanner combo
17" crt monitor
P3-800 (fully loaded)
another creative 4.1 speaker setup
5 port switch
comswitch for phone/fax
various other power adaptors and devices

All of this doesn't even pull 300 watts (it's running at 270 as I type).

Throw a LCD monitor at it and you could drop that draw by 50 watts or so.

A power inverter will work just fine, I'd go for the 350 watt model. The closer you get to it's maximum, the hotter it will run, and the shorter it's life will be.
You could also get a small UPS and use that as a go-between, it would also give you some warning before shutdown. Most of the inverters will automatically shutdown at around 10 volts, and they don't give any warning when they do.
 
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Old 04-10-08, 07:54 AM
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Sure, you can swap out your current 200W ATX power supply for one that has a 12v dc input. They can be expensive (unless you find one on eBay), and they are kind of hard to find. They have the same form-factor, and slip right in place of the existing supply. Most are good for down to 10V, so it should survive the voltage dip during engine start-up.
 
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Old 04-10-08, 08:40 AM
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This thread is 3 years old. He probably figured it out by now.
 
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Old 04-10-08, 08:53 AM
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True that, but there may be others interested in doing the same thing. Anywho, this is a rather uncomplicated way to do it.
 
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