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-   -   Make a 3 Pin fan run without a PSU (http://www.hardwarecanucks.com/forum/troubleshooting/21293-make-3-pin-fan-run-without-psu.html)

BobbyLou July 28, 2009 12:54 PM

Make a 3 Pin fan run without a PSU
 
can these be done. I dont have like a any type of PSU. I got some 3 pin to molex but no computer standard atx PSU to test them on at the moment. Any ideas?

Arinoth July 28, 2009 01:04 PM

Unless you have an electronic's power supply, you may have to parallel wire some batteries together to gain 3, 5 or 12V. You have to be careful with that though, they all need to be brand new or you can potentially damage the batteries or the fan

krazyups July 28, 2009 01:04 PM

Do you have any AC - DC wall adapters? They would work if you could figure out some way to connect to them. Pretty much any wall adapter will do, I know most are unregulated, so you will be providing as high as ~17Vdc when you first connect them (for a ~12V adapter, that is), but the voltage will come down rapidly as the load increases.

EDIT: Or you could do something like Arinoth suggests, just get a 9V battery and power them up.

BobbyLou July 28, 2009 01:15 PM

ok thanks guys. how would i do the 9v power up? ( sounds more practical and easier)

Arinoth July 28, 2009 01:21 PM

Quote:

Originally Posted by krazyups (Post 232074)
Do you have any AC - DC wall adapters? They would work if you could figure out some way to connect to them. Pretty much any wall adapter will do, I know most are unregulated, so you will be providing as high as ~17Vdc when you first connect them (for a ~12V adapter, that is), but the voltage will come down rapidly as the load increases.

EDIT: Or you could do something like Arinoth suggests, just get a 9V battery and power them up.

I always forget about the damn 9V batteries. Just wire it up, make sure you wire the leads correctly (though best of my knowledge its a motor and so if you wired it backwards it should just spin in the opposite direction, theoretically anyways)

3 of 7 July 28, 2009 01:37 PM

I've been running a 120mm 12v fan behind my woodstove for over a year with a 2a 12v wall adapter for over a year. works great. I just used 2 of the 3 wires.

DarKStar July 28, 2009 10:29 PM

Exactly - you want to be using the right 2 wires - as the 3rd one is used for the RPM sensor, so you won't be needing that obviously :)

MpG July 29, 2009 12:23 AM

If you try a 9V, keep an eye on it at first. Dry-cell batteries have notable internal resistance that can make bad things start to happen at higher current levels. Hopefully, a single computer fan (~0.15-0.4A) wouldn't be enough to be a problem, but it's possible that you could see the battery begin to warm up over time. This is one time where running multiple batteries in parallel could be quite useful to reduce the current load on each cell.

krazyups July 29, 2009 05:29 AM

Quote:

Originally Posted by Arinoth (Post 232090)
I always forget about the damn 9V batteries. Just wire it up, make sure you wire the leads correctly (though best of my knowledge its a motor and so if you wired it backwards it should just spin in the opposite direction, theoretically anyways)

Actually, computer fans usually have a diode in place to prevent reverse voltage from doing anything, so if it shouldn't spin up at all if the voltage is reversed. :thumb:

Running multiple batteries in parallel is a good idea, but since you just want to test them, you'll probably just test one at a time.

-Steve :canadianwave:


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