Removing fans from a circuit that has a sensor

Discussion in 'General Electronics Chat' started by Nicholas, Jun 3, 2008.

  1. Nicholas

    Thread Starter AAC Fanatic!

    Mar 24, 2005
    121
    1
    Hi all!

    I have a couple of fans I want to remove from a monitor, but if I just
    remove them the monitor kicks in with a warning on the CRT and then
    shuts down.

    So how would I go about removing them? inserting a resistor in place, if
    so do I need to match the resistor wattage to the fan wattage?

    Thanks!

    Nicholas
     
  2. paulktreg

    Distinguished Member

    Jun 2, 2008
    611
    120
    Nicolas

    It might not be that easy. Have the fans got three or four wires rather than just the two? (Red & Black)

    In all likelihood the fans have tachometers (like CPU cooling fans) which give out a square wave pulse in proportion to the speed. The monitor is probably seeing it as fan failure and shutting down.
     
  3. Nicholas

    Thread Starter AAC Fanatic!

    Mar 24, 2005
    121
    1
    Hi!

    The fans only have two wires!

    Thanks!
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The monitor is likely complaining because it is getting too warm.

    The fans were originally installed to cause sufficient airflow to remove the heat generated by the components.

    If you want to remove the fans, you will have to make up for their removal by supplying sufficient airflow by some other means.

    It may also be that the monitor has circuitry that detects the "gaps" between the commutators of brushed fans. If it doesn't see those "gaps" occurring, it assumes that the fans have stopped running, and thus shuts down. If you really must circumvent that (and risk burning up the monitor) you could build an astable 555 timer circuit that oscillates at around 4kHz, and connect it up to the fan power supply. That should generate sufficient power spikes that it will fool the monitor into believing the fans are still running. Until it melts down, of course. Then you can throw it away and buy a flat panel LCD monitor.
     
  5. Nicholas

    Thread Starter AAC Fanatic!

    Mar 24, 2005
    121
    1
    "Then you can throw it away and buy a flat panel LCD monitor"

    No way:) I hate those things. This monitor weighs 98kg, that's cool!;)
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I suspect that if you wish to keep using the monitor, you may also have to let the cooling fans be. They are not there because the designers thought they sounded real purty.
     
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