# Wiring A Computer Fan



## Batz (18/2/07)

Anyone know how to wire up a computer fan,it has 3 wires.one I believe one is a pulse output.
Also where's the best place to source a 12v power supply for this?


Cheers
Batz


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## SpillsMostOfIt (18/2/07)

If your computer fan has a third wire, it will almost definitely be for a thermistor which tells some intelligence in the computer the temperature of air flowing through the fan. You can ignore it. Chances are that the wires will be red, yellow and black. The red and black will be the ones you want for the fan and the third can be ignored.

Assuming it is a 12 volt fan (most of them are - the most common, but declining alternative is 240V), a cheap plug-pack from Jaycar will work just fine - they draw two-fifths of very little power (in the scheme of things).

There may be direction of flow and rotation arrows on the case of the fan. If you wire it up so that the red is positive, these arrows will be correct.

Edit for pedantry: Some computers (mainly server-class) will use the thermistor to help diagnose a fan failure.


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## PostModern (18/2/07)

For further pedantry, the third wire will be a pulse to indicate the speed that the fan is rotating, not temperature. 

Batz, wire red and black to +ve and -ve 12V DC and you'll be fine. They generally draw decimal points of an amp, so any cheap plug pack will be fine.

EDIT: Most PC fans will run (but slower) on lesser volatages. So 9V will do, 7 at a push and 5V if you don't mind giving the fan a hand at starting.


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## Ross (18/2/07)

Batz,

Have a look around for an old mobile phone charger, these usually work great.

cheers Ross


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## FNQ Bunyip (18/2/07)

Ross said:


> Batz,
> 
> Have a look around for an old mobile phone charger, these usually work great.
> 
> cheers Ross




Xmas lights, camera, printer, torch, drill ect ect ect you will probly find 3 or 4 laying around by the end of the day that don't have anything to do, any will work.


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## SpillsMostOfIt (18/2/07)

PostModern said:


> For further pedantry, the third wire will be a pulse to indicate the speed that the fan is rotating, not temperature.
> 
> Batz, wire red and black to +ve and -ve 12V DC and you'll be fine. They generally draw decimal points of an amp, so any cheap plug pack will be fine.
> 
> EDIT: Most PC fans will run (but slower) on lesser volatages. So 9V will do, 7 at a push and 5V if you don't mind giving the fan a hand at starting.



I've not encountered fans providing tachometric pulse outputs outside of CPU coolers. The ones I've been harvesting thermistors from came out of IBM desktop machines and Compaq Proliants from the mid-late 1990s and were general cooling fans (although some of them were pointing at the CPU heatsink).

Either way, unless you're overcooking a fan solution, you only have to worry about red and black.


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## QldKev (18/2/07)

Have a look at second hand shops, some carry old phone chargers. Mine is a 12v 500ma from an old (reeealy old) motorolla phone. But otherwise many places like Dick Smith will have 12v power packs new, just ensure you have enough to run the fan. The fan I'm using is 0.3a (300ma), but they do vary; often a lot smaller than this.


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## Wortgames (18/2/07)

This thread is beginning to look a lot like this one - might be worth a read Batz.

I think just about every DC power option was covered there pretty well.


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## Batz (18/2/07)

Thanks guys,wiring sorted now..red and black forget the yellow  

I think I have found a 12v charger as well

Cheers all

Batz


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## PostModern (18/2/07)

SpillsMostOfIt said:


> I've not encountered fans providing tachometric pulse outputs outside of CPU coolers. The ones I've been harvesting thermistors from came out of IBM desktop machines and Compaq Proliants from the mid-late 1990s and were general cooling fans (although some of them were pointing at the CPU heatsink).
> 
> Either way, unless you're overcooking a fan solution, you only have to worry about red and black.



Pardon my ignorance, but why would anyone care about the temperature of the fan? Temperature of your components matter, not the temperature of the hub of a fan. I'm pretty sure 99% of the time you'll find the yellow monitoring wire measures rpm of the fan, giving either 3,4 or 6 pulses per revolution, depending on model. 

There are some temperature sensor fans (ie speed up when things get hot) such as this one, but they come with an external thermistor to mount on the component that the fan is cooling. The third wire leading into the fan hub has always, in my experience, been a fan speed sensor.

Either way Batz, you don't need to worry about it


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## SpillsMostOfIt (18/2/07)

PostModern said:


> Pardon my ignorance, but why would anyone care about the temperature of the fan? Temperature of your components matter, not the temperature of the hub of a fan. I'm pretty sure 99% of the time you'll find the yellow monitoring wire measures rpm of the fan, giving either 3,4 or 6 pulses per revolution, depending on model.



Dunno, frankly. But thankfully some engineers at IBM and HP thought it was a good idea to measure the temperature of the air as it passed by - perhaps it is their 'over-all system' temperature sensor. Works for me, though, because the thermistors are really nice and small, which suits my current application. The fans I have are all labelled Nidec Beta V TA350DC. Nidec (http://www.nidec.co.jp) claim to still offer similar products.


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## Trough Lolly (18/2/07)

Batz,
Here's a pic of my magnetic stirrer using a PC fan to spin the magnet...



Cheers,
TL


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## Batz (18/2/07)

Trough Lolly said:


> Batz,
> Here's a pic of my magnetic stirrer using a PC fan to spin the magnet...
> View attachment 11506
> 
> ...




I have one of those TL,this ones for inside my keg serving freezer.

Batz


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## Wortgames (18/2/07)

Hey Batz, be careful about using a 12v battery charger - it will probably be putting out 15 or more volts.

The fan will run nice and fast, but its life will be shortened accordingly. That's fine if you don't mind the thought of replacing the fan from time to time, but if you want it to last then it would be worth getting a REGULATED 12v DC power supply - about $18 from Jaycar or get one out of an old PC.


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## Batz (18/2/07)

I have a power supply from an old modem.

Fans stuffed but :angry: 
I'll try a computer shop later in the week,I have to go into Gympie 
Batz


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## SpillsMostOfIt (18/2/07)

Batz said:


> I have a power supply from an old modem.
> 
> Fans stuffed but :angry:
> I'll try a computer shop later in the week,I have to go into Gympie
> Batz



Before spending money, can you confirm (for your own purposes) that the power supply is good? I once spent several months cussing the purchase of a cheap 'amplified indoor tv/fm antenna' before realising that the plug pack was the issue. Of course I felt quite stupid for a while after that (well, more than usual).


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## Batz (18/2/07)

SpillsMostOfIt said:


> Before spending money, can you confirm (for your own purposes) that the power supply is good? I once spent several months cussing the purchase of a cheap 'amplified indoor tv/fm antenna' before realising that the plug pack was the issue. Of course I felt quite stupid for a while after that (well, more than usual).




Yes the power supply is good
That does not however stop me being stupid  

Batz


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## shonky (18/2/07)

Hi Batz.

Is that the fan that I sent you? If so it was defintately working when I sent it, I tested it using a mobile phone charger.

Cheers

Jon


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## Batz (18/2/07)

I may have been mate,me an electrical things don't mix  

Batz


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## Screwtop (18/2/07)

This is getting way too complicated. The yellow wire is for connection to an alarm should the fan stop, if required depending on the application, so it is an rpm monitor kind of, you don't need it Batz. Next, these things are DC voltage devices and can tolerate variance in supply voltage so grab a cheap plug pak, any regulated PS for $18 is not going to be much better.


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## Batz (18/2/07)

Screwtop said:


> This is getting way too complicated. The yellow wire is for connection to an alarm should the fan stop, if required depending on the application, so it is an rpm monitor kind of, you don't need it Batz. Next, these things are DC voltage devices and can tolerate variance in supply voltage so grab a cheap plug pak, any regulated PS for $18 is not going to be much better.




I think I said in an earlier post I understand the yellow wire is not reqiured (not to hard even for me)
I also said I had a 12v voltage supply from an old modem.
Not really to complicated in my terms,except I killed the fan before I knew this :lol: 

And that I did without the aid of my glasses


Batz


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## Fingerlickin_B (18/2/07)

Batz, 

I've a got a brand new and positively enormous 240V fan here, maybe 4-5" wide, alloy housing, ball bearing runners and everything...but I've also got no use for it. 

You want it? If so, PM me your address and I'll send it COD...you pay the postage cost only, I'll wear the rest :beer: 

PZ.


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## Screwtop (19/2/07)

Batz said:


> I think I said in an earlier post I understand the yellow wire is not reqiured (not to hard even for me)
> I also said I had a 12v voltage supply from an old modem.
> Not really to complicated in my terms,except I killed the fan before I knew this :lol:
> 
> ...




Mean't the replies were becomming too complicated, as you say, it's simple stuff!


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## bindi (19/2/07)

QldKev said:


> But otherwise many places like Dick Smith will have 12v power packs new, just ensure you have enough to run the fan. The fan I'm using is 0.3a (300ma), but they do vary; often a lot smaller than this.




I have one of those Dick Smith power packs that you can dial in 12,9,6, 3 and I think 1.5 V and have found my fan [0.3a] runs best at 9V  .


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## Batz (19/2/07)

bindi said:


> I have one of those Dick Smith power packs that you can dial in 12,9,6, 3 and I think 1.5 V and have found my fan [0.3a] runs best at 9V  .



That's good to know,thanks Bob

Batz


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## Doogiechap (19/2/07)

It might be best to keep that puppy out of the freezer as the thermal load of the larger motor will equate to the compressor running for longer/ clocking up bigger power bills. Go the PC fan  
Cheers
Doug


Fingerlickin_B said:


> Batz,
> 
> I've a got a brand new and positively enormous 240V fan here, maybe 4-5" wide, alloy housing, ball bearing runners and everything...but I've also got no use for it.
> 
> ...


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