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Forum Index : Electronics : Running my PCs off 12V
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| adric22 Regular Member  Joined: 06/08/2008 Location: United StatesPosts: 47 |
When I get my wind/solar setup going, I was wondering if it would be more efficient for me to convert all of the computers in the house to run off of 12V. I've seen these DC-DC ATX computer power supplies like these: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350089198 192 I have two computers that run 24 hours a day. One is a fileserver the other is a security camera server. Both are small, low power computers. Incidently, the cameras run on 12V too. So I was wondering if I would save a significant amount of power by converting their internal power supplies to run off 12V rather than upconverting from 12V to 120V and then the computer downconverting back to 12V again internally. I have 2 other computers in the home too that run most of the time. (albiet in standby mode) |
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piercy007 Newbie  Joined: 27/06/2008 Location: United KingdomPosts: 28 |
Adric I would have thought it would depend on how you intend to set up your battery bank system. Are you intending to use a 12v or 24 volt system. I would simply convert that to what ever output you need with an inverter. If you change your equipment you then have to change it on any future upgrade or change. Better to maintain standard end user eqipment and adjust your supply than try to retro fit the PC's. I would also check whether these power supplies will support you in heavy use. I have a similar camera and it does not really peak but your file server and the other PC's may depending on usage My middle name is luck mind you my first is bad! |
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
If you are serious about driving all those computers, perhaps change to laptops instead. ........oztules Village idiot...or... just another hack out of his depth |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I no longer use the desktop PC. I exclusively use laptops and palmtops. I have 3 data logging units that have a combined consumption of less than 10% of 1 desktop PC. My internet laptop[using currently], a Toshiba Portege is currently using 15W. If you are serious about reducing energy consumption, then running a PC is out the window. Gordon. become more energy aware |
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| adric22 Regular Member Joined: 06/08/2008 Location: United StatesPosts: 47 |
These PC's I use are not your typical juice-hogging PCs. Granted, I'm sure they use more than a laptop. They are tiny little Compaq 1.0 Ghz units and I think their power supplies are rated at 100 watts or less (compare to 400 to 600 watts on home built units) but what they actually draw from the power supply, I'm not sure. But I do know that PC power supplies are very inefficient because they tend to use voltage regulators and giant heat sinks to cool them. So I suspect I could save 50% of the power simply by running them from 12V. There really isn't much to retrofit, by the way. The power supply can be removed from these units in about 20 seconds, there aren't even any screws. It is a standard ATX connection so it would essentially be "plug and play." But then one has to consider, how long would it take to recoup the $40 I spend on each power supply in energy savings? I suppose one advantage would be that my systems keep running during a power outage. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Your link does not work try this you will still have to supply 30-40A @ 12 to run them all. Fair sort of ask, but better than using an inverter up to mains and then back to computer 12v I guess. You will be pushing up daisies before payback probably, because you still have to sort out how were getting that 30-40A@12v bit sorted. 
........oztules Village idiot...or... just another hack out of his depth |
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| Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221 |
If they are genuine compaq machines dont expect off the shelf supplys to mechanicaly slot straight in. Many of the brand name machines have odd shaped supply cases. OK read before you speak Robb. Those are nothing like the 12volt PSUs I'v seen before. |
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| adric22 Regular Member Joined: 06/08/2008 Location: United StatesPosts: 47 |
No they are not, But I've measured and the replacement will physically fit in the machine. So I'd just need to rig a way to hold them in place and make sure there is a fan blowing since the original P/S is also the computer's only fan. |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Adric22, This is a little off topic! I have an Amiga1000 phoenix motherboard, only 500 of so units worldwide. Do you know much about these? Gordon. become more energy aware |
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CraziestOzzy Senior Member Joined: 11/07/2008 Location: AustraliaPosts: 135 |
I would avoid Compaq power supplies. They have their own mysterious terminals and wiring. But you have complete Compaq units, so the following still applies. On your typical ATX, you may be able to remove the 240v pcb board and make your 12 volt connections on the main board just past the 240v - 32/24/12 volt transformer. Or better still, you might even try adding your connections for 12volt voltage to the third PCB compartment where the 12 volt inputs are...where those huge torroids sit and all the wire come out. ATX power supplies are easy to work on and they are generally clearly set up into three or four different sections, determined by looking at the solder trace on the underneath side. The 12 volt side is usually just past the opticouples. Your biggest hurdle is the amperage you will need to meet, as already stated. The reason I would use a part of the original ATX power box is that the 12 volt compartment has all the filters etc to protect your MOBO and I recall that the PWM is also on the 12 volt side, handy for reducing constant power drain (but may be wrong without looking at one again). http://cr4.globalspec.com/member?u=25757 http://www.instructables.com/member/OzzyRoo/ |
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| adric22 Regular Member Joined: 06/08/2008 Location: United StatesPosts: 47 |
CrasiestOzzy, You are right. I have thought about supplying 12V right to that spot on the power supply as well. But I sort of figured that after being converted to 12V by a transformer, it would be further downconverted to 5V. If they use a transformer for that, it would need to be supplied in alternating current for the transformer to work. But honestly, I'm not sure how they are doing it after that point. |
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| adric22 Regular Member Joined: 06/08/2008 Location: United StatesPosts: 47 |
Have you been watching my youtube videos or something? Well I know a lot about the Amiga 1000 and its motherboard, but I have never heard of this "pheonix" that you describe. So, I can't help you there. |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
hi adric22, The Amiga1000 phoenix was a custom dropin replacement for the A1000. Mine incorporated K1, K2 & K2.1 in ROM. It had onboard HDD port and fatAGNUS. Mine had custom 4MB RAM expansion that I built. I was a consultant on the design team. We were imortalised with our names incorporated in the PCB artwork. Mine is now mounted on display at home like a work of art. Gordon. become more energy aware |
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Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
I doubt there is much merit to run your PC on 12V. The line drop will kill any inefficiencies you are trying to save. The diagram here http://www.pavouk.org/hw/en_atxps.html looks to me like a typical ATX power supply circuit. It has a transformer straight from primary to the different voltage outputs through multiple taps. No room for a 12V input I'm afraid. Though if CraziestOzzie is right, you still might have a chance if your topology is different. One thing we could all think about is switching to high voltage DC for our RE houses. It sounds like a revolutionary step, but when you think about it, most devices are happy with DC. Compact fluorescents work on DC, most switchmode power supplies, all incandescents, most printers, computers, and many newer TVs etc... Some good high end computer UPS systems are popping up on the market stating that their output is DC. This is very interesting. The benefits are a very cool and efficient running step up converter that maximises battery life. But how about using small AH 12V batteries to get 240V directly. 20 x 12V batteries would get to 240V. OK, charging them and keeping them balanced would be a feat, but if this problem was overcome, you would not need an inverter at all. 100% efficiency. |
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| adric22 Regular Member Joined: 06/08/2008 Location: United StatesPosts: 47 |
[quote]It sounds like a revolutionary step, but when you think about it, most devices are happy with DC. Compact fluorescents work on DC, most switchmode power supplies, all incandescents, most printers, computers, and many newer TVs etc... [/quote] I'd be surprised if many computers would run from high voltage DC. Anything that has a transformer would require AC, and every computer I've ever seen has one. |
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| Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
They have transformers in them but they are switchmode power supplies. The first thing that happens is the AC is converted to DC then chopped into high frequency then fed to the transformer. By using a high frequency, there is no need for a large transformer, hence the product is cheaper and lighter and the output is easier to regulate. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Just a word of caution . . . as far as I am aware there are significant safety issues with high voltage DC systems. Especially, ones that are capable of significant amounts of current. |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi davef, you are quite right. DC usually makes the muscles contract and there is the possibility that you hang on, if electrocuted. AC tends to throw you off. Either way, the higher the voltage the more the hazard. Gordon. become more energy aware |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I think from a electrocution angle hv is hv and not healthy, and I have been stung by more hvdc than hvac but much of a muchness. The real safety issue is from DC arcing in switching contacts. The fire hazard from arcs that won't extinguish with hv dc is the real problem that I would consider as a practical preclusion to using HV DC around anywhere without specialised switch gear. If I was worried about electrocution from dc, I wouldn't play with switchmode supplies... and how dull would that be? ...........oztules Village idiot...or... just another hack out of his depth |
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| adric22 Regular Member Joined: 06/08/2008 Location: United StatesPosts: 47 |
I think the whole "high voltage" thing is a misnomer. I've been shocked by a million volts before and it barely hurt. But that is because it had almost zero current. A lot of people don't realize that very low voltage can be deadly if there is enough current, where as no amount of voltage will kill you without some current behind it. They should change all those warning signs to "high amperage" |
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