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fan speed switching?

Discussion in 'Electronic Basics' started by mike, Jul 22, 2003.

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  1. mike

    mike Guest

    Being completely clueless on circuit design I thought I'd try this NG to
    seek some inspiration!

    I have a standard 12v fan I'd like to toggle between two different speeds
    using a momentary action switch. The fan speed is currently being changed
    using a 62 ohm 7 watt ceramic resistor to drop the supply power.
    I really havent got a clue where to begin.
    Any pointers gratefully received!

  2. Rich Grise

    Rich Grise Guest

    Connect the switch across the resistor. When the switch is closed,
    the fan runs fast. When the switch is open, the fan runs slow.
    If you still find this confusing, I'd strongly recommend looking
    up some basic tutorials - they're all over the place - try and search for "electronics tutorial" or
    some such. From time to time, other regulars post links to
    basics sites, too.

    Good Luck!
  3. cpemma

    cpemma Guest

    Easy with a SPST toggle switch, but with a single *momentary* switch you'll
    need something like a flip-flop driving a relay switch across the resistor,
    with anti-bounce on your momentary switch.

    There are some circuits on Terry Pinnel's site, including
  4. mike

    mike Guest

    Thanks so far people. The circuit on the quoted url seems ideal.
    The fan is rated at 2.4w (200ma?) so maybe I'll need to use the relay
    circuit as well.
    Looks like I have some reading to do!

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