fan as dc load

Discussion in 'General Electronics Chat' started by haran, Apr 19, 2012.

  1. haran

    Thread Starter Active Member

    Apr 6, 2008
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    i have connected two computer fan's rated at 12v and 0.14A each in parallel to a12V 0.5A supply. Does this mean that im supplying higher power to the fans thus making them spin faster?:confused:
     
  2. Felo

    Member

    Feb 20, 2012
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    The fan's will pull only the amount of current they need, just think that a computer supply can give 20 or more amps in 12V, so why won't the fan spin it's way to outher space then?

    I=V/R(Z)
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    No 0.14A is the rated current each fan will draw during normal operation. So the fans will not spin faster.
     
  4. Felo

    Member

    Feb 20, 2012
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    Just don't connect them to supply > 12V, Then they will spin faster and possibly burn useless.

    Good luck
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Actually they won't. Ever open up a fan? They use electronics, so the speed is probably constant, depending on the circuitry. More voltage will just burn up the chippies inside.

    Another thing to always be aware of on a fan, never use compressed air to spin them up. The counter EMF from the spinning blades will blow them faster than you can say stop. Been there, done that.
     
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  6. vpoko

    Member

    Jan 5, 2012
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    That's great to know, I've done that many-a-time before (luckily without any problems) but will be careful not to do it again.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I usually use a toothpick or some such to hold them still when blowing them out.

    Older AC fans are much simpler, and don't have this problem.

    A typical DC fan has 6 electromagnets aligned in a circle, the fan blades have magnets in the hub that following the sequencing electromagnets. The one I opened had on 8 pin chip, one capacitor and one resistor (RC oscillator).
     
  8. haran

    Thread Starter Active Member

    Apr 6, 2008
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    so what u guys mean is that its the fans will only spin at rated speed although im supplying higher then rated ampere's to them? and the will spin faster if i supply them with higher voltage?
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    Yes that it correct. Then using the correct voltage. The fans will draw the current they need. The mains power system can deliver a lot of ampere. But if you connect a bulb rated for use on main power lines. A 1 Watt bulb will only draw 1 Watt, and a 100 Watt bulb will draw 100 Watt.
     
  10. haran

    Thread Starter Active Member

    Apr 6, 2008
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    but wont the fan be damaged if i give it lets say 24V, 2A supply?
     
  11. #12

    Expert

    Nov 30, 2010
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    That is a different question. Giving too much voltage to a fan...read post number 4.
     
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