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Pot rating?

Discussion in 'Electronics & Electrics' started by effekt26, Nov 8, 2006.

  1. effekt26

    effekt26 Member

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    Hi everyone, im going to be building my own simple fanbus/rheobus fan speed controller, and i have a question...

    what size pot/poteniometer do i use? the guy at the elec store didnt know so i thought i would ask before i bought...

    Thanks, Justin
     
  2. nux

    nux Member

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    Voltage drop across pot * Current through pot

    There are many better ways of regulating a fan than just one pot too.
     
  3. OP
    OP
    effekt26

    effekt26 Member

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    and what wattage...

    also, what other methods?

    Cheers, Justin
     
  4. GooSE

    GooSE New Member

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    The wattage is what nuxie1 mentioned.

    Voltage drop across pot * current draw through pot = nominal wattage of pot
     
  5. wabbit

    wabbit Member

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    Hi effekt26
    If you can show us a circuit diagram we can advise you better.
    There are several methods such as series resistor, adjustable voltage regulator and pulse width modulation.
    Cheers
    Rob
     
  6. OP
    OP
    effekt26

    effekt26 Member

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    i know i need a ~6 watt pot...so i figure roughly 10k OHMS of resistance is ok??

    Cheers, Justin
     
    Last edited: Nov 8, 2006
  7. Goth

    Goth Grumpy Member

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  8. wabbit

    wabbit Member

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    You would only need a six watt pot if the fan was drawing half an amp.
    Three Watt wirewound pots should be fine and are readily available from Dick Smith Electronics in values from five Ohms to 10K for $9 each.
    Cheers
     
    Last edited: Nov 10, 2006
  9. GooSE

    GooSE New Member

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  10. OP
    OP
    effekt26

    effekt26 Member

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    ok, say i have 2 fan, both use roughly 2.1 watts of power.

    if they are connected like the diagram below, will it over load my 3 watt pot.

    [​IMG]

    Thanks, Justin
     
  11. kizzap

    kizzap Member

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    looks exactly like the setup i have on my fans. works alright too

    EDIT: I was actually incorrect when i said that was correct and how i had it connected up...

    remove the 5 volt supply and it should be right.

    to calculate the size of the pot i would need to know the current that the two fans would be drawing
     
    Last edited: Nov 10, 2006
  12. wabbit

    wabbit Member

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    Hi kizzap
    What resistance value pot did you use?
    Also, it looks like you're using the 12 and 5 volt supplies together so you only get a variation of 7 volts. Is this correct?
    Cheers
    Rob
     
  13. OP
    OP
    effekt26

    effekt26 Member

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    yes, i want it to range between 7 and 12...do?? please see this thread for issue regarding the voltages...

    http://forums.overclockers.com.au/showthread.php?p=6600091#post6600091

    thanks, Justin
     

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