daisychaining 2 (or more) ATX computer PSU

[dpuch]

Using the last image Posix posted I made this up for the 36 and 48v versions. If you use gimp (open sorce paint program) you can view the .xcf file to turn on and off the 36v and 48v versions. Or just compare them to each other and the 24v version above.

Dale

[NC Cams]

I have the link to this thread pasted into my "info cheat sheet".

Will repost it when situation requires a future response. Hopefully, this thread will be used as a standard reply to any further "how do I use a PC power supply?" inquiries....

Thanks to posix and dpuch for their artistic and technical comtributions to the community.

[h_2_o]

you might have to register (hopefully not) but this might help some out

http://forums.bit-tech.net/showthread.php?t=108208

[obscurity]

Does it matter if the power supplies don't match? I have a 250watt AT style power supply and a 480watt Serial ATX style supply.

Can I join these together? Does it matter which one has its chassis ground clipped

thanks
John

[NC Cams]

If you drew full power from the 480 watter, you'd potentially be running the 250 watter WAY overcurrent.

Yes, it does matter BIG TIME which ground is clipped.

Here's how to do it:

http://www.cnczone.com/forums/showth...015#post142015


Do it this way (post #9 and #13) and ONLY this way and don't get creative.

Why? Reread post #9 in provided link.

[obscurity]

Ok I understand which ground should be clipped relative to the diagram but which supply should I make the green one? Or are you saying that regardless of supply I put in the green position I run a good chance of burning up the 250 watt supply?

Sorry for my density,
Thanks for your help,
John

[NC Cams]

Look at the daisly chaining of power supplies with the same logic as if you tried to hook up a thoroughbread horse and a mule in series to pull a wagon....

Poor match, no???

The horse would easily outrun the mule (speed wise) but the mule could probably outlast the horse in its abilty to pull over the long term.

The small power supply is component sized (as in the output current pass elements) so as to support THAT amount of power. The BIG one is sized in a like fashion.

What do you think will happen if/when you ultimately may get to the point of shoving 480 watts thru the pass elements of a 250 watt P/S regardless of where you mount either P/S in the chain??? I don't know for sure but I wouldn't want to find out because I"m not that curious.

To simplify life, I'd use matched P/S's....

[xyz100]

Word of caution. As far as I remember power supply case is connected to ground. Hence if two daisy chained power supplies connected by the cases it will short one of them.

[NC Cams]

XYZ100: The link in post #17 addresses that issue.

This is also the reason the same post emphasizes "not getting creative - do it as indicated"

Good to emphasize that part about ground clipping no matter what. Hoever, I'm sure SOMEONE will ignore or forget that part of the directive.

Sort of technicaly dyslexia.

[gregsnovas]

i herd somewhere that you can get 24 volts out of a single atx power supply by using the negitve logic instead of the ground

http://www.tc.umn.edu/~beck0778/powersupply.html

[fyffe555]

Originally Posted by gregsnovas i herd somewhere that you can get 24 volts out of a single atx power supply by using the negitve logic instead of the ground http://www.tc.umn.edu/~beck0778/powersupply.html

yeah but the -12v is only rated to 0.5A, so if you need 24v at under 0,5a you're ok..

[NC Cams]

To add to fyffe555's reply, the chain is only going to be as strong as its weakest link...