How do I juice my second power supply without hacking my first one?

[Slacker]

I have room for a second power supply and was planning on using it for fans, I would like to set it up so it turns on with the main power supply when the computer is started, but I would like to do this without hacking the wires on my main power supply, is there a way to use one of the spare floppy power plugs on the main power supply to send the turn on signal to the second power supply?

 

[Vrangel]

I doubt its possible the way you want,
but check this guide. anyway.

 

[bacillus]

hehe, I hope that your signature is not an omen for your proposed modification!

 

[medic]

More Info:

and here:

 

[Slacker]

Wow, no, I am not going to do all that, I was hoping for a simpler solution, but the cigarette lighter mod is cool

What about putting together a pigtail, like the splitters used to power two devices from one plug, if I were to get two of the female plugs off old atx motherboards and hack the male plug and wires off an old atx power supply to make a connector with one male end to connect to the motherboard with two female ends to attach power supplys, would the second power supply need all of the wires connected to it or just the wires that send the signal to turn it on?

 

[Slacker]

LOL at what bacillus said

Thanks CRV, checking it out now.

 

[Slacker]

Thanks CRV, I can do those mods, I should be able to either extract the wires from the plug and do the connections at the pin or put in a 2to1 connector inline so it will be reversible, what about those "clamp on" splitters used in car stereo installs? you just put it on the wire you want to draw from and lay the cut end of the leech wire next to it and clamp it shut, any reason not to do it this way?

Here is a link to a picture of the connector I am talking about,

Insulation Displacement Connectors, Self-tapping (IDC) Tap-And-Run Connectors, Using only ordinary channel-lock pliers, these color-coded connectors make quick, reliable, pre-insulated splices without stripping, twisting, soldering , or the need for special tools.

 

[sohcrates]

i've used those "clamp on" connectors to hook up fans in my computer before, so you could definitely use them.

 

[medic]

They are "good enough" but I may be a little of a perfectionist in that in splicing wires in computers or cars I always strip the wire about an inch or so, tightly twist the new one in, solder them together and then use some split shrink tubing and heat and your done.

If you don't like soldering, pick up a small bag of solder tabs, small sticks of solder that you wrap around the two wires and then heat with a match.

PS
If you remove the wire from the plug first you won't need to split the shrink tubing.

 

[Jhhnn]

You could do what you want with one of these, and only hack the wiring on one unit, or get two and hack the wiring on neither psu. Be sure to run some 5v load on the second psu, otherwise it won't be happy.

Extension

Oh, yeh, you don't have to connect the grey to black on the second psu- don't know why some people think so.

I'm sure that you could build a momentary "ON" trip circuit with an ic timer chip, too, never tried that myself.

 

[Slacker]

What is the relationship of the power supplys in this situation? what if the second power supply went bad, could it take the main power supply down with it?

it looks like if there was a short to ground on either power supply they would both fry :Q

Should I put a fuse inline before the connection to the main power supplys wiring? if so, what amp?

(again with the car stereo wiring parts )

I could use an inline fuse like you see in car stereo/amp setups (either blade type or barrel type, I would think blade would be better, I have seen the barrel type pop apart when they get old or hot)

Or is this even neccessary?

 

[Slacker]

Hmmm... Now that is what I was looking for, Thanks Jhhnn, I could make my two splices on that extension cable and leave my main power supply intact

Be sure to run some 5v load on the second psu, otherwise it won't be happy
Umm.... what would be 5v? fans are 12v right?

And what about the interaction of the power supplys, it is probably a slim chance that one could damage the other, is it worth worrying about?

 

[Jhhnn]

Something like a CDROM or HDD on the second psu will give it some 5v load. Or a resistor, like this-

PCP&C

No known probs with interaction, they really don't interact except on the green wire & common ground. If you're terribly concerned, the green wires could have isolator diodes- you'd probably be the only guy in north america to go to the trouble.

 

[Slacker]

This is why I love this place, I now know exactly what I need to do to accomplish what I wanted to do, Thanks everybody