lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 5:54 pm

how to hook up two independent computer power supplies, in series?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
bill142
Posts: 7853
Joined: Wed Aug 04, 2004 1:50 pm

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 6:18 pm

uhh.. why?

how are you intending to use them? one to power mobo and cpu and another to power cd and hdd?
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 9:13 pm

Quoting Bill142 (Reply 1):
one to power mobo and cpu and another to power cd and hdd?

Kind of like that, I want one to turn on when the other does.
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
trvyyz
Posts: 1331
Joined: Thu Oct 21, 2004 9:19 am

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 9:21 pm

If your are using two power supplies(PS), I imagine you would be connect two ac mains cable (that makes it parallel automatically). The output side (dc side) all the connectors are polarized (does not allow you to connect the wrong connectors to the internal devices), so you can connect to whatever devices in Computer from both PS. So, just select the loads in so that you distribute the loads coming to each PS evenly.


In short, you need not worry about series or parallel, just hook up the primary sides to the ac and keep connecting the dc(secondary) side as though they were from a single supply.

[Edited 2006-11-12 13:25:44]
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 9:38 pm

Quoting TRVYYZ (Reply 3):
In short, you need not worry about series or parallel, just hook up the primary sides to the ac and keep connecting the dc(secondary) side as though they were from a single supply.

Would I need to splice wires or an adapter?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
RichardPrice
Posts: 4474
Joined: Sat Apr 23, 2005 5:12 am

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 9:42 pm

Watch out for different earths, even to the same wall socket, it can kill a computer (Ive done basically what you want to do here, and I lost parts due to a differential in the earths on the two supplies).
 
TedTAce
Posts: 9098
Joined: Sun Mar 27, 2005 12:31 am

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 10:43 pm

Dude, unless you are an ET (which apparently you (as well as me) are not) this is stupidity.

If you don't have enough energy comming out of a power supply to power your stuff, butch up and buy a bigger power supply. If you want redundancy, buy a case/motherboard that is designed for dual power supplies. Sure your spending money but you'll be a lot happier when you watch the system power up properly instead of letting the smoke out of the caps.
This space intentionally left blank
 
Klaus
Posts: 20578
Joined: Wed Jul 11, 2001 7:41 am

RE: How To Hook Up Two Computer Power Supplies?

Sun Nov 12, 2006 10:51 pm

Do not do this. Especially as long as you don't know what you're doing.

It is very likely that you're simply frying both power supplies that way.

If you need a stronger PSU, get one. There is no cheap way around it, especially not this way!
 
Queso
Posts: 3109
Joined: Sat Jul 08, 2006 12:28 pm

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 1:38 am

Quoting Klaus (Reply 7):
Do not do this. Especially as long as you don't know what you're doing.

It is very likely that you're simply frying both power supplies that way.

If you need a stronger PSU, get one. There is no cheap way around it, especially not this way!

 checkmark  Agreed. What it sounds like you are trying to do can be done, but not in a way that is easily explainable in a forum.
 
trvyyz
Posts: 1331
Joined: Thu Oct 21, 2004 9:19 am

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 1:41 am

Quoting Lehpron (Reply 4):
Would I need to splice wires or an adapter?

I don't think so, if do it the right way.

Quoting RichardPrice (Reply 5):
Watch out for different earths, even to the same wall socket, it can kill a computer

Be sure to interconnect the two earths/grounds of the two PS on to the Chassis of the PC. I believe you are using two power supplies made specifically for use with PC's and not any ac adaptor lying around.

Also be sure to have a multimeter and you can check for any voltage between the the grounds of two the PS on the dc side before connecting(make sure it is zero V).

As everybody mentioned, margin for error is very small and all protection of PC is on the primary side of PS and not on dc.

[Edited 2006-11-12 18:06:09]
 
trvyyz
Posts: 1331
Joined: Thu Oct 21, 2004 9:19 am

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 2:18 am

Another problem I can see with this arrangement is that, if one PS fails, it could overload the other PS and damage it depending on the circuitry.
 
Klaus
Posts: 20578
Joined: Wed Jul 11, 2001 7:41 am

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 4:54 am

Quoting TRVYYZ (Reply 9):
if do it the right way.

There is no "right way" to do this with off-the-shelf PSUs!

This is much more complicated than just the question of connecting which wire where - and conventional PSUs are simply not built for load sharing, which would be an absolute necessity.

Keep your hands off if you don't want to risk destroying your computer and the PSUs, quite possibly involving a risk of fire for which no insurance would ever reimburse you.
 
AC773
Posts: 1700
Joined: Wed Nov 30, 2005 6:03 am

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 5:09 am

Quoting Klaus (Reply 11):
Keep your hands off if you don't want to risk destroying your computer and the PSUs, quite possibly involving a risk of fire for which no insurance would ever reimburse you.

It could potentially be worse. In a standard power supply, certain capacitors can carry enough electrical charge to kill you. Anything over 16 joules will do the trick.

Bottom line? Unless you know what you're doing, don't mess around with power supplies or, for that matter, any kind of computer or electrical component.

A PSU of adequate wattage is a lot cheaper than the price of the components you might fry, the fire you might start, or the ambulance ride you might need.
Better to be nouveau than never to have been riche at all.
 
trvyyz
Posts: 1331
Joined: Thu Oct 21, 2004 9:19 am

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 8:52 am

Quoting Klaus (Reply 11):
There is no "right way" to do this with off-the-shelf PSUs

I don't know about the background of the threadstarter or whether he can do it.
It is not easy but not impossible. I work in a lab and we like to experiment these kind of things, may be thats why I find it challenging. The fire hazards are minimal if an approved PS is used ie, UL or TUV mark. They have to be tested for almost all possible faults. In my lab we blowup PS almost every other day  Wink because some of our techs don't change the voltage setting and plug to 240V (Canada is 120V,60Hz)

[Edited 2006-11-13 01:14:04]
 
lehpron
Posts: 6846
Joined: Tue Jul 10, 2001 3:42 am

RE: How To Hook Up Two Computer Power Supplies?

Mon Nov 13, 2006 10:06 am

Quoting AC773 (Reply 12):
A PSU of adequate wattage

I just need amps on the 12v line, specifically 3 more than what I have, so a small 120W or 180W supply was considered but how to hook up is not obvious to me yet.

Edit: (warning, crazy idea, I just came up with it now): how about hooking up a 12v battery, how much current is there?

Quoting TRVYYZ (Reply 13):
I don't know about the background of the threadstarter or whether he can do it.

Might as well just spit out the whole thing:

My power supply is a Hiper 580W (620W peak) with a combined dual 12v rail maximum of 30 amps. It's pretty good, very quiet, had it for 4 months and I like it. As it stands, I am using approximately 23amps on the 12 volt line at around 290W.

Most of ya'll might know my plan with adding a TEC onto my computer's graphics card:

  • nVidia GeForce 7900GT KO 512meg version.

  • Stock speeds 560/1500MHz.

  • Currently, overclocked 685/1600 MHz.

  • My idle/load temps are 39*C/51*C (Rthdribl.exe for 10mins at full res).

  • Through empirical testing Qout idle/load is 44/70 watts

  • memory chips estimated at 4W each (x8), never measured their temps (I'll get some heasinks for them later).


  • I guess the recent idea (last night) was if I had 7 amps left, why not get a tiny TEC to experiment - but would it make a difference? Even an 80W TEC at 12v would cool no more than 32W worth. I'd need more cooling that the core put out at load to be effective, but those modules are power hungry. That would begin at the 169W, 172W and 226W versions -- that is only if I stop overclocking the core.

    I know how TEC's work, they require up to 2.5 times the power to run than to cool. I have thought of many combinations of doing this with 8 different TEC's including giving the thing its own power supply. I'm not using a water cooling loop as the cpu cooler that was modded onto the gfx card can remove up to 150watts of heat, double what the card is putting out now at 685MHz. I have noticed that whenever I turn on the AC (not usualy on), I can increase the speed with no change in idle/load temperatures!

    I suppose theorhetically, if I moved the computer to the AC cranked it to supercold and began OC'ing some more, I may not need the TEC. Maybe I can use up all the 7 amps left over into the graphic card if I just turn on the AC, the cooler should take it all. I wonder if I could reach the 800's MHz on the core on air cooling? The maxiumum possible is 1120MHz and the highest I've seen online was on the 3Dmark06 benchmark all-time-highs at 1020MHz using custom phase change cooler (cheapest commercially available solution I've seen was $400).

    Other people on other tech forums brag about their speeds and they have spend hundreds in liquid cooling but here I am, having spent $65 and my core is running faster. I want to see how much faster I can push it.

    I wonder, is it absolutely neccesary to get it cold, if all the heat is removed, why not maintain ambient? I have considered PWM TEC controllers bu those things are expensive and I have $150 to play with as of now. I might try the AC idea first before the TEC thing.

    Quoting TRVYYZ (Reply 10):
    Another problem I can see with this arrangement is that, if one PS fails, it could overload the other PS and damage it depending on the circuitry.

    Hmm, for some reason I keep thinking in terms of t=0 on this, and not the idea that the second psu would fail so soon it would cause me problems.

    [Edited 2006-11-13 02:24:26]
    The meaning of life is curiosity; we were put on this planet to explore opportunities.
     
    trvyyz
    Posts: 1331
    Joined: Thu Oct 21, 2004 9:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 11:31 am

    Quoting Lehpron (Reply 14):

    Let me discuss with the hardware experts in my lab for a second opinion.
    I am more of a power guy, I thought synchronising a 3 phase alternator to the power grid was challenging. I enjoy more of the 10kV surges we simulate and 5kV hipots we do.
    Let me see if I can get the detail on the advantages and disadvantages of the arrangement.

    Also, your computer enclosure will be heated more due to all the loads and many of the components many not be rated for this ambient, so the ventillation could be a problem or it will act as heating chamber or unless you are not using an enclosure which then is a safety issue. Most of the component temps should not exceed 90oC and 105oC is the limit for PCB for safe operation.

    [Edited 2006-11-13 03:47:00]
     
    trvyyz
    Posts: 1331
    Joined: Thu Oct 21, 2004 9:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 11:42 am

    Quoting Lehpron (Reply 14):
    12v battery, how much current is there

    The rating of the battery is given in ampere-hours (Ah). If you divide the Ah by the current you draw, it will give you the number of hours it can supply that current.
    Anyway not recommended.

    I have tested li-ion batteries of 3.7V and it gave upto 34A on short circuit (only for a second or two) and then about 12-14A for about 10 minutes. Short circiut of a AAA baterry cangive upto 4 or 5A upto a few minutes.
    Please note: We have a fire extinguisher handy when we do the crazy tests Wink
     
    RichPhitzwell
    Posts: 1285
    Joined: Mon Jul 24, 2006 5:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 1:22 pm

    you could do a wake on lan... but that usually requires a second MB and NIC. as for starting up two power supplies without all that hassle, Crestron makes a devise that starts and turns off computers with the press of a button. I should warn you, this is a hard boot. cost a couple of hundered dollars.... of course you could do the same thing with a standard switch and some bios settings... if thats all your after.

    anyways, im drunk
    =)
    Nonav.com kinda like Whiners except the lights are on and the pimps been paid
     
    TedTAce
    Posts: 9098
    Joined: Sun Mar 27, 2005 12:31 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 2:06 pm

    Back to the fucking TEC shit again  Sad

    I should have known better...

    Lephron, just say  no 
    This space intentionally left blank
     
    RichPhitzwell
    Posts: 1285
    Joined: Mon Jul 24, 2006 5:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 2:38 pm

    ok, so im not as drunk as before...how are you able to get 23 amps out of anything...most single phase breakers commercial are only 20 amps. residential is either 15 or 20 amps.... most desktops including crt monitor on startup are around 5.2ish amps... now im really curious, please explain!
    Nonav.com kinda like Whiners except the lights are on and the pimps been paid
     
    TedTAce
    Posts: 9098
    Joined: Sun Mar 27, 2005 12:31 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 2:51 pm

    Quoting RichPhitzwell (Reply 19):
    now im really curious, please explain!

    You don't want to know.... Instead of using a fan, liquid, liqud nitrogen, or anything else that normal people user to cool his system: Rocket boy wants to use what's called a Thermal Electric cooler. I fell in love with the technology when I saw it on a motorcycle helmet (in 1988) and that made some sense. Then I fell out of love when I read some of the earlier threads on this subject and read how much energy it takes, and how poor the efficiency is. The boy might as well use a catheter; with the right tubing and lighting it should look pretty cool.
    This space intentionally left blank
     
    RichPhitzwell
    Posts: 1285
    Joined: Mon Jul 24, 2006 5:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 3:03 pm

    Quoting TedTAce (Reply 20):
    You don't want to know.... Instead of using a fan, liquid, liqud nitrogen, or anything else that normal people user to cool his system: Rocket boy wants to use what's called a Thermal Electric cooler. I fell in love with the technology when I saw it on a motorcycle helmet (in 1988) and that made some sense. Then I fell out of love when I read some of the earlier threads on this subject and read how much energy it takes, and how poor the efficiency is. The boy might as well use a catheter; with the right tubing and lighting it should look pretty cool.

    Yes but he said he is drawing 23 amps now.. im curious how he is able to do this in the usa off of a 110v 20a circuit unless he is using a 220, 277, 440...circuit.
    Nonav.com kinda like Whiners except the lights are on and the pimps been paid
     
    DrDeke
    Posts: 805
    Joined: Sat Jun 11, 2005 7:13 am

    RE: How To Hook Up Two Computer Power Supplies?

    Mon Nov 13, 2006 4:04 pm

    Quoting RichPhitzwell (Reply 21):

    Yes but he said he is drawing 23 amps now.. im curious how he is able to do this in the usa off of a 110v 20a circuit unless he is using a 220, 277, 440...circuit.

    When he says 23 Amps, he means 23A at 12V on the DC rail of his power supply. That's 276 Watts, quite easy to obtain from a 115VAC 15A circuit, even with PSU overhead  Smile.

    -DrDeke
    If you don't want it known, don't say it on a phone.
     
    trvyyz
    Posts: 1331
    Joined: Thu Oct 21, 2004 9:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 2:08 am

    My discussion results:
    Can be done. But is it worth the trouble? Only if you are an enthusiast and willing to take chances.

    Some links on some people who have done things like this:
    http://www.moddin.net/review.asp?ReviewID=34&PageNo=1
    http://www.abxzone.com/forums/showthread.php?t=72633
    http://www.abxzone.com/forums/showthread.php?t=32829

    Didn't read the whole thing but seems mainly how to turn on the PS by shorting the green and black wires of the motherboard connector.
     
    RichPhitzwell
    Posts: 1285
    Joined: Mon Jul 24, 2006 5:19 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 3:30 am

    Quoting DrDeke (Reply 22):
    When he says 23 Amps, he means 23A at 12V on the DC rail of his power supply. That's 276 Watts, quite easy to obtain from a 115VAC 15A circuit, even with PSU overhead .

    Ahh, never try to do math when drunk off your arse!
    Nonav.com kinda like Whiners except the lights are on and the pimps been paid
     
    David L
    Posts: 8547
    Joined: Tue May 18, 1999 2:26 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 3:41 am

    Quoting TedTAce (Reply 20):

    He's going to design us a cheap, environmentally friendly SST on it. Leave him alone!  Smile
     
    lehpron
    Posts: 6846
    Joined: Tue Jul 10, 2001 3:42 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 4:59 am

    Quoting TedTAce (Reply 20):
    Instead of using a fan, liquid, liqud nitrogen, or anything else that normal people user to cool his system: Rocket boy wants to use what's called a Thermal Electric cooler

    The lowerest temperature a fan will 'cool' is ambient, no matter how many rpms or cfms there are. I'm usually in an environment with no AC. since most liquid systems use fans in their radiators, same thing, except is takes longer to heat up and loose heat from a liquid. Nitrogen? If you're familiar with commercially available PC cooling that involves the stuff, please be my guest and tell me its not over $500? Most liquid systems, i cant fit the fans, pump, resevoir anywhere in my case. I just want video cooling, not cpu. For my case TEC's are cheaper.

    Quoting TedTAce (Reply 20):
    I fell in love with the technology when I saw it on a motorcycle helmet (in 1988) and that made some sense.

    Awe...how was a TEC used in a helmet?

    Quoting TedTAce (Reply 20):
    Then I fell out of love when I read some of the earlier threads on this subject and read how much energy it takes, and how poor the efficiency is

    Purely ideally all the power in should convert to cooling. Realistically ideally, half the power in would cool the rest is waste heat. But, like any other mechanical device, in real life machines are not so highly efficient. They waste more heat than do their intended work. If anything you, should be ticked (if not already) that your car's gasoline enigne is no better than a TEC, at most 35% efficient. Most TEC's are 40%, IMO, that is damn good. If I wanted efficiency then I'd go for the 437W module at a surprising 48%, but its power hungry.

    Quoting TRVYYZ (Reply 23):
    Didn't read the whole thing but seems mainly how to turn on the PS by shorting the green and black wires of the motherboard connector.

    however tempting, I saw what looked to me like a relay device in your second link, might have to investigate the avilability.
    The meaning of life is curiosity; we were put on this planet to explore opportunities.
     
    sprout5199
    Posts: 1681
    Joined: Sat Feb 26, 2005 8:26 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 5:19 am

    Quoting Klaus (Reply 11):
    There is no "right way" to do this with off-the-shelf PSUs!

    This is much more complicated than just the question of connecting which wire where - and conventional PSUs are simply not built for load sharing, which would be an absolute necessity.

    Keep your hands off if you don't want to risk destroying your computer and the PSUs, quite possibly involving a risk of fire for which no insurance would ever reimburse you.

    Listen to Klaus. We use 24v-50amp PSs for our microwave system and transmitters where I work. If we need more than 50 amps we buy 2 PS but one is a master and one is a slave, I.E. use one to regulate volts and current in both PS. Either one can be master but you have to set them up correctly. very expensive, I think around $5000 each.

    Dan in Jupiter
     
    TedTAce
    Posts: 9098
    Joined: Sun Mar 27, 2005 12:31 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 9:33 am

    Quoting Lehpron (Reply 26):
    TEC's are cheaper.

    Until you get your electric bill.

    Quoting Lehpron (Reply 26):
    Awe...how was a TEC used in a helmet?

    http://www.freepatentsonline.com/4483021.html

    http://www.freshpatents.com/Crash-he...ling-dt20060518ptan20060101556.php

    The application I saw had the he radiating fins running from front to back of the helmet on the top in a strip about 2 inches wide by 4-4.5 inches long.
    This space intentionally left blank
     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 10:48 am

    Connecting two power supplies in series: 12+12 = 24 V

    -no problem, if you keep the ground and case of the "top" one isolated. It's easiest to resolve this by finding the spot where the common ground secondary potential inside the power supply is connected to the case and disconnect it, that is, leaving the black power ground wires "floating" from the case. The protective earth on the primary side must remain as it is, and be connected to the mains as usual. It might be a good idea to connect a, say 500k resistor between the floating ex-ground and the real ground for routing any stray currents in cases when only one P.S. is operating. Starting the "top" one must be done through a relay, or one half of a double-acting push-button switch. (The "Start" wire of the P.S. be grounded momentarily to the ground of the respective power supplies, note).
    I may have to add that the high voltage part (the mains) has nothing to do with the setup. Those AC wires are totally free to go in any order.

    -Many variations are possible, like 5+5, 12+5 etc. The "top" P.S. really does not know nor mind that his ground is the other's 12V, or whatever. The current limiting facility will be like before as both will see the same current.


    Connecting several P.S:s in parallel for a larger amperage: not really workable. The eventual load distribution mismatch will lead to a shutdown.

    [Edited 2006-11-14 03:08:08]
    "Nukkuessa tulee nälkä" (Nipsu)
     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 10:56 am

    Quoting Sprout5199 (Reply 27):
    Keep your hands off if you don't want to risk destroying your computer and the PSUs, quite possibly involving a risk of fire for which no insurance would ever reimburse you.

    The components in approved power supplies will by regulations not propagate fire even if they are heated to the exteme by a fault themselves. It's extremely difficult to light up a fire by misusing an approved switching mode computer power supply.
    "Nukkuessa tulee nälkä" (Nipsu)
     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 11:15 am

    Quoting AC773 (Reply 12):
    It could potentially be worse. In a standard power supply, certain capacitors can carry enough electrical charge to kill you. Anything over 16 joules will do the trick.

    The chances of a kill are small, but you might receive a jolly good jolt. That is if you're acting really fast -- the discharge (bleed) resistors that will always be installed across the caps will do their trick in 20-30 seconds

    [Edited 2006-11-14 03:16:58]
    "Nukkuessa tulee nälkä" (Nipsu)
     
    Bobster2
    Posts: 1523
    Joined: Mon Jan 17, 2005 3:04 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 2:27 pm

    What about all the external devices with separate power supplies? Why can you have separate DC power supplies outside the box but not inside the box?
    "I tell you this, no eternal reward will forgive us now for wasting the dawn." Jim Morrison
     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 9:33 pm

    Quoting Bobster2 (Reply 32):
    What about all the external devices with separate power supplies? Why can you have separate DC power supplies outside the box but not inside the box?

    That's a good question, and there's a short answer. The lab supplies' "0" output line is not connected to the metal case/ground as it is in the computer power supplies. They have a separate ground connector.
    "Nukkuessa tulee nälkä" (Nipsu)
     
    sprout5199
    Posts: 1681
    Joined: Sat Feb 26, 2005 8:26 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 10:26 pm

    Quoting WSOY (Reply 30):
    The components in approved power supplies will by regulations not propagate fire even if they are heated to the exteme by a fault themselves. It's extremely difficult to light up a fire by misusing an approved switching mode computer power supply.



    Quoting WSOY (Reply 31):
    The chances of a kill are small, but you might receive a jolly good jolt. That is if you're acting really fast -- the discharge (bleed) resistors that will always be installed across the caps will do their trick in 20-30 seconds

    Its thinking this way that get people killed and buildings burned down. Any time you misuse any PS you are asking for trouble. I have seen too many PS with faulty crowbar circuits, bad limiters, and wrong size fuses. And if you trust bleeder resistors, you are asking for trouble. Believe me, fires do happen. I have opened a lot of equipment, and seen the aftermath of fire. the only reason they go out is no more oxygen inside the case.

    Dan in Jupiter
     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 11:16 pm

    Quoting Sprout5199 (Reply 34):
    I have opened a lot of equipment, and seen the aftermath of fire. the only reason they go out is no more oxygen inside the case

    So have I, accidentally. Modern computer switching power supplies by the way do not apply Crowbar circuitry. That was in the analog times. We have now a set of analogue comparators (in a single IC package) that directly shuts down the power supply controlling chip. I've not seen an open fire in a modern power supply, ever.
    "Nukkuessa tulee nälkä" (Nipsu)
     
    sprout5199
    Posts: 1681
    Joined: Sat Feb 26, 2005 8:26 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 11:32 pm

    Quoting WSOY (Reply 35):
    That was in the analog times. We have now a set of analogue comparators (in a single IC package) that directly shuts down the power supply controlling chip. I've not seen an open fire in a modern power supply, ever.

    The PS that I use still have them, astrons and such.If it aint broke dont fix it. More of a brute force PS than anything else. 40 to 50 amp supplys.

    I guess what I trying to say is don't mess with the PS. If you need a bigger one, go buy it, don't try to hook 2 together. Just asking for trouble---been there, done that, let the smoke out.

    Dan in Jupiter
     
    runway23
    Posts: 1914
    Joined: Sat Jan 15, 2005 2:12 am

    RE: How To Hook Up Two Computer Power Supplies?

    Tue Nov 14, 2006 11:43 pm

    Use a pince, they roughly look like this:

     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Wed Nov 15, 2006 2:59 am

    Quoting Sprout5199 (Reply 36):
    The PS that I use still have them, astrons and such.If it aint broke dont fix it. More of a brute force PS than anything else. 40 to 50 amp supplys.

    There really is no need to use a crowbar circuit in switching mode supplies, and none of the consumer grade units I've seen in the past 10-15 years have had one. In the linear mode supplies there was a considerable amount of energy stored in the solid iron core of the transformer and the smoothing caps that only could be contained by a shortcircuiting or "crowbaring". In the modern swithing mode supplies the energy is transferred strictly by a pulse-by-pulse basis and these pulses are very short in duration. When the train of pulses is stopped, there's no element in the unit that would store energy any longer. Hence the intrinsic safety of the switching mode supply. The downside is that the primary circuit side is very much "alive" and any faults often end in a bang-bang breakdown of various semiconductor cases.

    I measured the charge potential on the primary side smoothing caps on one P.S. The unit featured a (typical) value of 470 uF and a bleeding resistor of 120kOhms. The operating voltage vas 160V that ran down to 50 volts in about 20 seconds after disconnecting. 48 volts is considered safe (SELV). So there's no reason for panic. I welcome any reference to a fatal accident resulting from a capacitor carrying similar charge.

    [Edited 2006-11-14 19:19:56]
    "Nukkuessa tulee nälkä" (Nipsu)
     
    sprout5199
    Posts: 1681
    Joined: Sat Feb 26, 2005 8:26 am

    RE: How To Hook Up Two Computer Power Supplies?

    Wed Nov 15, 2006 3:36 am

    Quoting WSOY (Reply 38):
    I welcome any reference to a fatal accident resulting from a capacitor carrying similar charge.

    Hmmm a challenge. see this: http://www.deprep.org/2001/TB01L25B.PDF

    page 3. not a "death" but mentions what we are talking about. was first thing i read on google for "fatal accident resulting from a capacitor ".

    Dan in Jupiter
     
    WSOY
    Posts: 822
    Joined: Tue Jun 13, 2006 10:24 pm

    RE: How To Hook Up Two Computer Power Supplies?

    Wed Nov 15, 2006 5:51 am

    Computer power supplies are nowhere near the high kilovolts range. Working back from the report get that the high voltage capacitor was 2mF and the energy "more that 30" Joules. This equals to a voltage on the cap of 5,500+ Volts! The internal inductance of the cap would probaly have been low, and the charge's rise time very fast with the high voltage being able to partly arch its way through.

    On a regular PC p/s we see 470uF*160V = 6 Joules (there are two such in a p/s) This is recognised (depending if you count the two caps into 1 or not, and some units carry 330uF or even smaller value caps) as falling into an U.S. electrical hazard class 1: "Once equipment is positively deenergized, personnel may work alone with minimum supervision. " http://psfcwww2.psfc.mit.edu/esh/minper.html
    "Nukkuessa tulee nälkä" (Nipsu)

    Who is online

    Users browsing this forum: No registered users and 6 guests