while planning on modding a computer i am getting through my friend i decided to make an external PSU to power all the extra stuff, such as , fans, cold cathode tubes, and other wonderous thingamajigs.

Anyhow how do i hook one up? is there some special procedure? If anyone has an idea on how to set up one i shall be on my modding way.

Thanks in avance

DarkSide

Can you post a pic of your case (even a pic of it at an online vendor) so we can get an idea what kind of space you have to work with? It may even be possible to mount it internally.

Also what is your existing psu? Does your case use a top blowhole? Were you wanting to mount on the top of your case or on the backside? If a smaller PSU will do the trick for that extra load you might be able to mount it sideways and squeeze it in the back left corner as long as you ventilate through the side and back and can still maintain a channel of airflow from front intake fans to get to your gpu. If you do that though you will want to mount it in such a way as can be easily moved (hinges from your local hardware store work wonders) so you can still work on your pc without snapping your wrist from odd angles

Or possibly turn your existing psu upside down so the intake is uptop (dont do this if you have a blowhole right in front of it) and put a thin sheet of fiber insulation beneath it and mount your second psu directly below it with the intake pointing downward, and exhaust fans for both pointing to rear of case

These are just ideas, I havent mounted a psu in such a way before but I "think" it would work depending on the size of your case

An AT power suppy would be the easier mod, as they can be powered without a mobo.

ATX PSUs are not supposed to work without a mobo connected (but we can mod around this).

So, you need to decide AT or ATX. Then you need to decide whether you want it completely independent or if you want it to power up when your main psu powers up.

Finally, where will you mount it?
In the case (as ablyss suggested)?
outside the case, but attached?
On the floor outside the case?

Are you comfortable with soldering etc.?

Let me know all that crap and I will get back to you.

I cant stress this enough This is NOT my case it is someone else who has brilliantly done a great job of modding his case. The one i will get is the base unmodded version of this case w would have posted that but i dont have a picture of it.

http://www.pcapex.com/modules.php?op...&orderby=dateD

thats what the case looks like

i feel comfortable with soldering as long as it doesnt do any of these things

Blow up
Cause all the lights on my block to go haywire
fry the PSU
or anything nasty for that matter

i want an external psu, whatever is easier is good although if it wont boot unless connected to a mobo... i might run into a problem... but as you said there are ways around these things.

and i know this will be kind of newb but atx means there are 2 plugs to the mobo and AT means one right if im wrong and its something completey diffrent, forgive me ive never run into this before. ill post a diagram of what i want to do with it later today although it will take some time

Thx to those who have posted and those who will post

DarkSide

The AT style psu is older than the current ATX designation.

Remember back when you had to manually hit your power button to kill your psu when windows said "it is now safe to shut down"?

That was because the psu was independent of the mobo. The mobo was just one of the things plugged in.

Now the psu shuts down automatically when windows closes, because the mobo controls the psu.

This is overly simplistic, but should be easy to understand.

So, if you can rip the psu out of an old pentium 2 or something of that vintage, you can just plug the psu in, turn it on (has a power switch in the back) and run stuff off it.

In order to use an atx psu this way, you must "trick" it into thinking it has a mobo connected. This is done by jumpering the green wire on the atx connector (the only green wire on an atx psu) to any of the black wires (grounds) on the same atx plug. IE. connect them with a wire.

Once this is done, the psu will automatically turn on when plugged in.

Now, you say you want to run fans and lights and gizmos off the external psu. I caution against this. An ATX switching psu has a safety mechanism built in. If you have only a few fans running, and then switch on your lights....the psu will (for some reason) shut down (and take all your fans with it).

What I have done (with absolute stability) is run only my mobo and HDD off the internal PSU. The cd drives, floppy drives, fans and lights all run off the external.

A general guide seems to be that an ATX psu requires 30% maximal load to run with any stability. So, you don't want your internal psu powering the entire system with the external running only fans and lights (tried and failed).

Couple final thoughts:

if you want the external psu to automatically power up with the pc you will need to splice the green wire into the green wire of the primary psu, and one of the black wires from the secondary to one of the blacks of the primary. This is instead of jumpering which I described previously.

Alternatively, you can just plug the secondary psu into the same master power strip as your pc. That way you turn on the powerbar and your secondary psu fires up ..... you then switch on your pc. If you forget the master switch (and thus your fans) the pc won't turn on.

If you plan to have the external psu outside the case (not connected at all) I recommend running a ground wire from the secondary psu case to the metal of your chassis just so all the electrical components in your case are grounded to the chassis. I am also probably overly cautious!

The beauty is you can make custom cables to your desired lengths so you can run 'em and route 'em and hide 'em. Then only 4 wires (neatly bundled) need to leave the back of your case to hook up to a single molex on the second psu down on the floor.

Hope this helps.

Let me know if you have further questions.

Absolutely, without a doubt, the longest post I have ever done!

I just re-read your post.

I can only tell you what has worked for me. I cannot guarantee that you will not screw anything up.

If you are not comfortable soldering and working with electronics....stop!

I know this is safe (I have done it) but I can't come over and do it for you. You work at your own risk!

If you find my previous post overwhelming or unclear, you are very likely in over your head. Search the net and find some guides, or at least come back and ask more questions before proceeding!

Good luck!

Good warning Putwig. I have run ATX's in tandem in a few comps, but ended up getting a rather large explosion off my last endeavor. Don't know why, PS's were matched, soldering was solid, insulation was good, it just blew up. That's when I decided to stick with an AT design for my second PS. You know, they are getting hard to find.

You can make an ATX PSU operate without a mobo if you jump pin four to pin six on the top row of the mainboard connection... Digital-World told me about that trick when I set up my first water-cooling rig and needed it to run without anything valuable inside. Here is a picture of how to do it.




If your Power Supply is over 300 watts and your system isn't massive, let it go for now, and maybe just spend 80 bucks later to get an Enermax or something.

This is kind of off topic, kind of, but I need to design an external power supply for my next project as well. Basically what I intend to do is run the wiring into a high-density connector on the side of the case, and then have that plug into a semi-standard ATX supply which has also has its ends replaced with the matching part for the high-density connector. That way I can easily connect the power by plugging and unplugging just one connector, and that also makes the power source a module, so it could very well be powered from a car instead of an ATX power supply, or a car battery, or a solar panel...the sky's the limit!

I see...

Well the comp itself doesnt need to much power outage so i was wondering how much a 12" CC takes up in watts. And i might just decide not to put an external one.

im planning one throwing in 3 fans(Ripped from old PSU's) and the cold cathode. i know how many watts the three Fans produce thanks to ducks posts but i havent found how many the cc takes up pls post.

Thanks in advance

DarkSide

i keep 2 AT psu's around for testing stuff... they are great.