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  1. #1
    Registered PepeLapiu's Avatar
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    Question 3x140mm fans auto controlled from mobo?

    Thanx and cheers!
    Last edited by PepeLapiu; 05-26-11 at 09:24 AM.

  2. #2
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    Maybe you can make an amplifier so that that one 4 pin connector powers some transistors that power all 3 of them. But you need to know what each pin of the 4 pin mobo connector does.

  3. #3
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    The Sunbeam Rheosmart 6 should fit the bill... can control 6 30w channels from the PWM header on mobo

    http://www.sunbeamtech.com/PRODUCTS/Rheosmart/6.html

  4. #4
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    Quote Originally Posted by PepeLapiu View Post
    Okay so I am not an electricity genius by any means (just the opposite) so this might be a stoopit question for the rest of you. And my Google sense doesn't shine today on this particular subject

    I want to have an external 3x120 rad with 3x140 fans on it.

    I would very much like to have automatic control of those fans.

    I understand some after market fan controllers can do that but then you have to rely on those ribbon temp probes and I don't really like those.

    I would rather have the mobo control the 3 fans based on the more accurate internal cpu temp.

    Hooking up a single case fan to the 4 pin cpufan connector on the mobo would be easy enough. But how can I get that 4 pin cpufan connector to control 3x140mm fans?
    I am guessing there would not be enough juice on that tiny 4 pin connector to power up all 3 fan, or is there?

    Thanx and cheers!
    i am sure there is not enough power on those 4 pins to control the fans, you would over load that circuit pretty quickly.


    i would suggest you get a controller, you can then control each fan individually that sunbeam reho would be perfect, almost overkill.
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  5. #5
    Member Khan's Avatar
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    the problem I forsee with this is unless you make a custom shroud for the 140's you lose a lot of static pressure on the fans from bleed off to the sides, what I would recommend is getting a rad like a swiftech or an xpsc that are made for low speed fans and get 3 scythe gentle typhoon 1450's on a fan controller.

    they have excellent static pressure and are quiet as fans in its class get.
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  6. #6
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    Quote Originally Posted by new/b View Post
    The Sunbeam Rheosmart 6 should fit the bill... can control 6 30w channels from the PWM header on mobo

    http://www.sunbeamtech.com/PRODUCTS/Rheosmart/6.html
    If he's only using 3 fans, a rheosmart 3 would be cheaper.
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  7. #7
    Low Profile Senior bing's Avatar
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    If those 3 140mm fans are PWM fans, its pretty easy, you just need to connect the pwm wire from each fan together and connect to the mobo header at the pwm pin.

    While the power pos and neg wires from all fans go to psu molex, so they wont load the mobo.

    For rpm monitoring, pick one of them and connect to mobo rpm pin. Rpm wire signal can not be joined together.

  8. #8
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    Be careful, .2 amps might be running amp draw. Startup amps can be double that.

    140mm fans don't have very good pressure charecteristics, so be forwarned, low speed 140mm fans might not work well with many rads. They just can't push the air through the rad.
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    With the smallish rad 1200 or 1300 RPM probably won't cut it. Smallish meaning what your wanting to cool for the rad you have. Especially if you overclock a lot. Push/pull would probably work, just buy twice as many fans. There just isn't a lot of good 2000 RPM 140mm fans yet that I know of.

    You do the math, a 120x4 is larger than a 140x3. 25mm is the standard thickness of most PC fans. They are okay. 38mm thick is the performance standard for mora cooling, usually with added RPM for the ones that can't do without.

    Please use this link to see what starting current vs rated current, use the very popular
    D1225C12B5AZ-00 one as I'm using it for current. I was way wrong. It's about FOUR times higher.
    .083 amps running, .360 for start up amps. Hmmm...............

    So, 3 of the .1 amp fans will have a start up current of, lets say 1.2 amps? Over 1 amp for sure.

    This fan isn't unusual, it's just one I know where the link is.
    http://catalog.nidec-servo.com/digit...pdf/D1225C.pdf

    So, please make sure on the fans first.

    Funny sig BTW.
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  10. #10
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    Quote Originally Posted by Conumdrum View Post
    You do the math, a 120x4 is larger than a 140x3.
    Actually, a 140.3 rad has more surface area than a 120.4.

    140.3 rad = 420*140 = 58800 mm2
    120.4 rad = 480*120 = 57600 mm2

    Speaking of Gentle Typhoons, the 1850s do have a startup current draw of 360mA. Running 3 of them would take it to 1080mA.

    I have the Asus P8P67 Deluxe. According to the manuals the max supported per fan header is 1Amp. I use a cable splitter and connect 3 GT 1450s per header with no problems since they're rated at 210mA startup draw per fan.

  11. #11
    Registered PepeLapiu's Avatar
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    At 1.08 Amps, I would use 3 GT1850 on a single header ...... only goes over the amperage rating by 0.08 Amp ..... for a couple seconds top.
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  12. #12
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    You can get a TIP31C transistor (or something els ein the 30 series). Mount it on a small heatsink. Run a fan tach line to the tach line on the MB. Run the the regulated power out line to the control lead on the TIP. Run 12v power in from a molex to the line in on the TIP and use the power out from the TIP to power the fans. It can handle up to 3 amps if mounted on a proper heatsink. some old 486 HS or the like. This should easily run 6 reasonably sized fans. If you need more use a higher rated transistor, the TIP40 series is rated at 6 amps.

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