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fan wiring


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#1
smalls101

smalls101

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Im gonna be honest, this question has nothing to do with my computer. Actually its more about my fishtank. I am upgrading the fans in there which are just standard case fans. They are wired up w/ just red n black wires and i am quite sure they are 12V. I want to just pull them out and stick some standard fans in there that are more efficient. I was just going to order 2 of these:

http://www.newegg.co...N82E16835119052

Now those fans have 3 pin connectors. From what ive been able to determine, black is just ground, and red/yellow are different voltages. Now if the power supply was 12v, which should i wire it to, the red or yellow? Also, is there a chance i could have a problem w/ amps? i really dont know what the current fans are drawing but if its not enough i could always just go to the pawn shop and pick up a dc adapter. I couldn't find anywhere how many amps these fans, or any computer fans for that matter, are drawing. Anyone have an idea?

tyia

Edited by smalls101, 28 December 2006 - 02:20 PM.

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#2
SRX660

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Red is the 12 volt line, black is the ground, yellow is the control wire that lets the motherboard control the fan speed. If you hook up just the red and black wires the fan will run at full speed all the time.

As for amps most 50 and 60 MM fans run at 0.8 to 1.0 amps. and since most computer fans are 12 volts the wattage would be around 10-12 watts. Most of the fans run in the same range


Vantec 80 mm Tornado Case Fan Sleeved
Model: TD8038H
Specifications:

* Dimension: 80X80X38 mm
* Rated Voltage: 12V
* Rated Power: 9.1 W
* Rated Current: 0.76 Amp
* Fan Speed: 5700 RPM
* Air Flow: 84.1 CFM
* Noise: 55.2 dB(A)

Just remember that:
Volts X Amps = Watts

A good multimeter would tell you what the voltage of the original fans are. A multimeter is also good for measuring amps too. Just something simple like this one. Buy one at your local Home Depot.

http://www.multimete...com/dt830bf.htm

You talk about using a DC adapter to run these fans. What i have done is found a working 12 volt AC/DC adapter with 3 or 4 amps ( at the local fleamarket)and wired the fans directly to the wiring after cutting the plug off the end of the wiring. If you want only 2 fans look for a 2 amp adapter. When they matrch up the fan amps and the adapter amps the fans will run fine without overspeeding themselves. Too many amps on the adapter will speed up the fans to where they are running too fast as there is no diode's to regulate the power.

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#3
smalls101

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Thanks for your help. Just one more thing though. If the fans are running at .8 amps, and you run 3 or 4 through them, isnt that a bit of a problem? or does the lower volts help? also, doesnt wiring 2 in series decrease the amps by half, or is it parallel? its been a while since i took my old electronics class
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#4
SRX660

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If you have a 2 amp adapter and wire 2 - 0.9amp fans in a series, it should not blow the fans because they will be pulling close to the 2 amps. If you were to wire the same 0.9 amp fans in parallel you would fry either the fans or the adapter because they would requireonly 0.9 amps. Either the fans would run wildly until they fried or the adapter would get so hot it melted. That is where it is tricky to do this without adding controller diode's to limit fan voltages.

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#5
smalls101

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Ok, so if i were to run 2 fans in parallel that were each drawing 140mA from a 12v 150mA power supply, they would only get 75mA each right? Will they simply run slower or will they over work the power supply and fry it?
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#6
SRX660

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I've done just that (very close to it anyway) and yes the fans ran slower and the adapter was hot but it did not fry. That is the beauty of these simple devices. They put out a wattage and do nothing more. That is why i would try to match the fans with the wattage of the adapter for best performance.

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