CPU fan wiring (3 wire) 2 wire power supply

Discussion in 'Grow Room Design/Setup' started by retik8, Jun 5, 2010.

  1. Here is what I am working with (pictures below). I think the power supply is good for this fan. Just seemed like the fan seemed a little slow so I wanted to make sure I wasn't going to fry it. Also was wondering if it matters if I hook two of these fans up in series to the same power supply. I don't think this matters but anyone with more electrical experience your response will be appreciated.

    Imageshack - img0049gb.jpg - Uploaded by retik8
    Imageshack - img0048kz.jpg - Uploaded by retik8
     
  2. #2 benthamj49, Jun 5, 2010
    Last edited by a moderator: Jun 5, 2010
    Do not hook them up in series. Parallel is what you want. You want to keep 12 V across BOTH fans and then you want the amps summing together. That thing can hold 3 amps, so just add up all the amps from all your fans and as long as its under three you won't be burning your house down.

    So yes, go ahead and do it but make sure both fans connect to the power supply directly, so they are in parallel not series.

    That means you will have 3 positive leads coming together (2 fans + 1 power supply) at one junction and then 3 negative leads coming together (2 fans + 1 power supply) at the other. And by junction I just mean a place where wires a coming together and will need to be soldered together and/or put electrical tape on and/or wire caps.

    And the reason for three wires on CPU fans is that one is positive, one is negative, and the third is a controller. High/Low fan speed. Not sure if the yellow needs to be activated to be on high but I dunno it'll work either way. Try to find CPU fans with two wires though, its easier and they're always activated in high.

    EDIT: You might be able to tell if its in a high or low state by testing those exposed connections with a multimeter or ammeter. If it reads +/- 0.02 from the 0.18 stated amps (with one fan connected) then it should be running in High.
     
  3. Thanks for your help. That makes a ton more sense! If I do find out that the fans are not running on high is there anything I can do?
     
  4. sorry I haven't replied sooner, it never showed up in my subscriptions. Yeah I dunno how exactly that control works. If you knew what voltage/amperage it takes to activate the switch you could probably plug a resistor in there to get the appropriate amount but I honestly have no idea. If it's low, go to newegg.com and just order a new one, 2 pin. Buy the cheap one, 3 or 4 bucks.
     
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