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Thread: CPU fan, PWM, Capacitors. Help.

  1. #11
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    Quote Originally Posted by mariush View Post
    What you need is a resistor or a potentiometer (variable resistor) - when you add one to the fan, the fan will no longer receive 12 volts but a bit less, therefore it won't spin that fast.

    Resistance value = Voltage / I - voltage is 12 v , i is the number that ends in A on the label of the fan - generally it's around 0.1-0.3A for regular 80mm fans.

    Assuming 0.15A, you're looking at about 80 ohm, so a 100 ohm potentiometer should be enough:

    http://www.amazon.com/100-Linear-Tap...3265794&sr=8-1

    Link is just to see how it looks, you should find them easily in retail stores around you.

    If you want something cheaper, just buy several resistors of various sizes between about 10 ohm and 100 ohm and use whatever value gives you best fan speed vs noise... I think you'll need to get resistors rated at 2w but probably lower ratings are also ok.

    For example: http://eu.mouser.com/Passive-Compone...z0z819Z1z0x6fr


    ps. and a simple tutorial: http://www.hardwaresecrets.com/article/79
    THANK YOU SO MUCH! I am going to try all this out! Thank you again! .

    Quote Originally Posted by Valis View Post
    If it's a PWM fan I suspect a resistor won't help. They're designed to be run @ constant voltage & duty cycle modulated by the PWM signal (which is a square wave). Fan controller is a better solution, and I fail to see how suggesting that is trolling.

    If it's a 3-pin fan you can just do the 7v or 5v mods, just google "7v fan mod" or "5v fan mod" respectively. No resistors required...
    a PWM fan is always 4 pin . Atleast in my case. As i have clearly mentioned. They may be designed to run at etc voltage and bla cycle, but my case is pretty different, if you didn't see. Its faulty and it runs every HSF at 100% all the time.

    Quote Originally Posted by walterm View Post
    Cutting the PWM wire should produce a three wire fan. (it can be spliced by your friend if needed) Or removing the PWM "pin" from the plug.
    If you have old parts to take connectors from your friend could solder wires from a molex plug to a fan male plug in the lower voltage configuration
    My feeling is counting the cost and time running around a new quieter fan is probably a simpler choice, a socket 775 stock cooler someone has laying around?
    Hmm as i will be adding a 4pin extender, i can do this too. I will try this and tell you the result. I do have an Intel stock HSF which is imo f'd by running at 100% all the time on this mobo. It did have lower noise but as i said it easily sounds like its going to die. and man lol i am not that of an amateur, that i cant even cut a wire . Soldering is what i will ask him to to do if need arise. i can solder too, but i am not a Professional.

    The PC i am making is for my sister. Not mine lol.

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    Quote Originally Posted by Serious Sam View Post
    a PWM fan is always 4 pin . Atleast in my case. As i have clearly mentioned. They may be designed to run at etc voltage and bla cycle, but my case is pretty different, if you didn't see. Its faulty and it runs every HSF at 100% all the time.
    Yea sorry I missed the part in the first post where you mentioned that it was a CPU fan, most of the boards I run now have 4 pin headers for all fans (and I was posting while working hence not being totally attentive).

    Imo you can either try the resistor method (no idea how well this works with pwm fans myself) or snip the 4th wire as suggested and look up the 7v & 5v fan mods, which essentially has you change ground to one of the lines carrying positive voltage. Combine the yellow & red lines = 7v mod (assuming polarity is right). The only caveat here is that you don't want to start the fan WITHOUT the computer as a load, and you'll typically want to make sure the power line you're using has other devices on the lines you're using and the PSU is decent enough quality. If the resistor method works with a PWM fan it may be 'safer' in terms of longterm usage...

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    I hope this isn't considered spam. If you can wait 2-3 weeks, a "12watt" internal fan controller (looks similar to the Zalman) is a 4 pin "cpu cooling fan" controller. It claims to control voltage (?) $4.59 shipped.
    Available from Hong Kong, therefore the shipping time.
    "OEM" intel heat sinks are also available cheap (from HK).
    Cooler Master 775 Heatsinks were on sale (quieter fan and bolt thru mounting for about $10), haven't noticed them lately though..

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    If you are feeling really adventurous, try this:

    http://www.nomad.ee/micros/pwm555.html

    All the parts are available at radioshack.
    Quote Originally Posted by JFK
    The American, by nature, is optimistic. He is experimental, an inventor and a builder who builds best when called upon to build greatly

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    Quote Originally Posted by 370forlife View Post
    If you are feeling really adventurous, try this:

    http://www.nomad.ee/micros/pwm555.html

    All the parts are available at radioshack.
    I can be adventurous if my pocket allows.

    Quote Originally Posted by mariush View Post
    What you need is a resistor or a potentiometer (variable resistor) - when you add one to the fan, the fan will no longer receive 12 volts but a bit less, therefore it won't spin that fast.

    Resistance value = Voltage / I - voltage is 12 v , i is the number that ends in A on the label of the fan - generally it's around 0.1-0.3A for regular 80mm fans.

    Assuming 0.15A, you're looking at about 80 ohm, so a 100 ohm should be enough:

    If you want something cheaper, just buy several resistors of various sizes between about 10 ohm and 100 ohm and use whatever value gives you best fan speed vs noise... I think you'll need to get resistors rated at 2w but probably lower ratings are also ok.
    Now can you tell me what exactly should i buy? like when i go and buy it, what should i ask for? a resistor with what specs?

    Fan is as usual 12V DC. Amperage is 0.6 which looks like its not a usual/regular . So i am looking at a 20ohm potentiometer? but the thing is i am not in favor of installing a potentiometer. Things wont get that hot (hopefully) that it needs rpm adjusting. I am looking at 2k and downwards.

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    Sad! I went today to buy the 4pin extender... and Nothing was available! Not even 4pin to 3pin!

    Now come on guys! Tell me properly! Which wire to cut to install the resistor? and what should i ask when getting the resistor?

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    Hello?

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    No offense but if you don't even know what the wires are or didn't bother to find out on your own using a 2-5$ digital multimeter, maybe you shouldn't be touching the cables.

    Anyway, generally the standard is:

    black - ground
    red - 5v
    yellow/in rare cases orange - 12v
    the fourth - pwm/speed sense.

    Since the fan is 12v (it should say so on the label, duh) you want to cut the yellow wire and put the resistor between the ends of the cable you just cut.

    As for what to get, get several values between 10 ohm and 200 ohm / 0.5w or 1w or 2w they should be a few cents each. Ok maybe not in Pakistan but still, shouldn't be that expensive. So get several and see what works for you - if it works at all. As others say, if the fan is with 4 wires, the circuitry in it may not allow the fan to work with anything else except 12v.

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    Quote Originally Posted by mariush View Post
    No offense but if you don't even know what the wires are or didn't bother to find out on your own using a 2-5$ digital multimeter, maybe you shouldn't be touching the cables.

    Anyway, generally the standard is:

    black - ground
    red - 5v
    yellow/in rare cases orange - 12v
    the fourth - pwm/speed sense.

    Since the fan is 12v (it should say so on the label, duh) you want to cut the yellow wire and put the resistor between the ends of the cable you just cut.

    As for what to get, get several values between 10 ohm and 200 ohm / 0.5w or 1w or 2w they should be a few cents each. Ok maybe not in Pakistan but still, shouldn't be that expensive. So get several and see what works for you - if it works at all. As others say, if the fan is with 4 wires, the circuitry in it may not allow the fan to work with anything else except 12v.

    Man look at it like this. Lets say you dont know anything or much about architecture/woodwork/etc. and you ask the expert something about it. and if he says 'You suck so bad, you shouldn't even touch the hammer'. What would you feel? Same here. I am not that of an amateur but what you are suggesting is trial and error. Which i cant do because... no 4pin extenders are available here. I feel so stupid! A simple thing like that is not available .

    Still THANK YOU! for replying. Resistors are dirt cheap. I dont know that which company is the best but local ones are dirt cheap.

    Cables are: Black, Red, Yellow, Blue.

    OK so yellow it is. I was thinking of red.

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    I must say i am pissed off at your huge suggestion. Forget o.5 to 2w, then you said 10 to 100ohm? Yes sounds easy but ask someone who doesn't know anything about them, to go buy them. There's nothing written on Resistors. I just picked 1 random from my friend, (which is 330ohm, who/how the hell to knows its watts? calculated here ) who himself didn't knew what i just asked him for. He said he just replaces the faulty one with new ones by matching the colors. You should have narrowed the search down. Ridiculous i must says.

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