How to turn computer supply o?

[Jerry]

Last year or so there was a posting on turning on a computer power supply.

I have a few supplies but most these days need a conection to the motoer board for turn on even if they have an onboard power switch.

Someone posted how to bypass this requierment. Does anyone remember or know how to?

I have a freind who's building a waist oil furnace. He will be installing 12 volt car ratiator fans in very thin wall ducts.

We've found that powering these fans at 3 to 5 volts moves the right amount of air  very quietly.

These motors only draw a few amps at this voltage. But how to we trick the computer supplies to turn on?

Thanks for info.

                           JK TAS Jerry

[jimovonz]

Short pin 14 (green wire) to ground (black wire - adjacent pin 15 is fine). You can find a pin out diagram here:

http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=pinconmth_atx_power

Some supplies require a minimum draw on the 5V line for proper regulation.

[hiker]

might be a over load on the pc trasformer with a couple of auto fans --even thou your underpowering the motors--just my thoughts their jerry....

[willib]

i agree with Jim , in most cases you will also need a dummy load of 1.3A on the 5v line, to get it to properly regulate..

so green wire to ground, and a 3.8 ohm resistor between +5V and ground.

Note : if your fans draw more than 1.3A then you dont need the resistor..

[dinges]

ATX powersupplies you have to 'switch on' as explained above.

If you use the older AT power supplies, they will operate when plugged in and the mains switch turned on.

The 5V can usually supply about 20A; the +12V about 8-10A.

You will need a load (usually on the +5V, sometimes also on +12V) for proper regulation, but I don't think this will be an issue here. Who cares when you get 6V instead of 5V (though 6V could mean instant to your PC motherboard), the fans will turn allright.

I recently converted two PSUs from 12V to 13.8V. Fun project, plus a good use of these old & abundant PSUs, but definitely not a beginner's project.

Good luck,

Peter,

The Netherlands.

[kitno455]

jerry- look for an AT supply. they have an actual power switch.

allan

[asheets]

computer power supplies are "switching" power supplies, and have to be under load.  I typically use an old 5.25" floppy drive as a load if I use a computer power supply outside of a computer...

[kitno455]

haha, only you and i likely have 5.25's around anymore. i actually have a combo 5.25/3.5 somewhere. i bought a pc by the pound to get it...

allan

[Jerry]

Hey thanks everyone for all your help.

                      JK TAS Jerry

[nothing to lose]

I have those 5.25 drives, also a new box of 5.25 disks, and at least one 10 or 20 MEG hardrive

 As for the power supply, as stated short the pins. There are new power supplies that have an on/off switch in the back and those that don't also. If yours has the rocker switch you can permantly short the pins and use the 110v switch on the back to turn it on and off.

 If you don't have a switch on back then you should be able to install a switch in your short to the pins. Closed shorted, open not shorted, and turn it on and off that way.

 A switch in the short is also useful for turning the supply on/off other ways, maybe use a thermosat in the short, if warm the power is off, if cold it turns on etc.. just depends what you want it to do, could come on at night and off durring day with a light sensor circuit or with a motion sensor turn on when it sees movement.

Almost all the power supplies I buy have the 110vac switch on the back, but I have had a few that did not also. I have a few newer ones scrapped from a computer shop that do not have the rocker on the back, they are all for new standard type systems and need shorted. The old ones for AT/XT systems did not need shorted. But just rather is has a switch on the back does't really mean anything.

I think my type DX4 100 power supplie did not need shorted either, it had wires that came to the front of the case and connected to a 110V rocker switch and also had the back switch on it.

As a matter of fact I have 3 newer systems in this room, one has a back switch one does not, didn't look at the 3rd.

[wiredwrong]

Your not the only one with 5.25's and boxes of new disk for them, but I also have a 8inch flopppy from an old mainframe that was in use until last year when the Homeland Grocery stores finally upgraded, its on loan to the college but I've been thinking about going to get it so I can tear it apart. Funny how the things from long ago are still around, and things from not so long ago are long gone.  

[nothing to lose]

I just found IBM MiCRO Channel cards, memory expansion, 4/10 (I think) network stuff in an old box of my junk at the shop trailer last night. Anyone need some large memory sticks, probably at least 64k each

Did not find the power supply I was actaully looking for though, from old IBMs, should have a few but not found yet. This post got me thinking of a use for them if I find them again.

[dinges]

You mean the PSUs with the big red switch (a large 'vane')?

Remember these too

For all of my electronics experimenting work (since '93), I've used an old PSU from an Apple-II (I think), a 'golden' power supply. Puts out +5, +12, -5 and -12. I've never yet needed anything else (with these voltages, you should be able to power just about any project, unless very special power/voltage is required). A year ago, this PSU quit on me, the 220V capacitor over the mains powerlines let out its magic smoke (probably old age). Quick fix with another one (X2 rated), and it was up again. You gotta love this kind of technology, it's possible to repair and keep it working till the end of times.

I love old PC power supplies too. Nice components inside, and when they're working, they're fine for powering just about anything. Even converted two to 13.8V at 10A (20A should be possible too, with more surgery).

And I've got a bag full of memory sticks too (plus boxes of 41256 memory ICs...), ancient enough to be worthless, but too young to be antiques...

Peter,

The Netherlands.

[asheets]

Don't tear that thing apart!!!  None of my students believe that they actually exist!  

The last time I saw an 8" floppy drive was the time I bought a "mystery" computer pallet at a government auction.  It was complete with about 300 pieces of media.  I converted that sucker to run with my Apple ][ (thought the stepper and the drive motor were both PMs and would have made great gennies...)

[asheets]

Sounds like a good 'ol IBM PC-XT supply.  You'll still need to put a load on it, but its good for 150 watts... (and the keyboard that came with it makes a good murder weapon).

[scottsAI]

Maybe I can save you some trouble.

The ATX supply has a 10watt 5v shutdown power supply for the motherboard.

You can use this without powering on the power supply!

A 12v, 2 watt fan at 5v draws maybe 0.5w, if it starts, some wont.

The 10w should be able to power several fans.

No need to worry about loading the power supply etc.

Have fun,

Scott.