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Digital resistor substitution?

Discussion in 'Electronic Basics' started by Glenn Ashmore, Feb 10, 2005.

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  1. Working on a circuit to control a refrigeration compressor speed. The speed
    is set by a resistor in the thermostat circuit that can range from 0 to 1.6K
    in a logarythmic progression. I have no documentation on exactly how the
    compressor's controller works but it looks like a basic RC network. Can't
    find a digital pot that would work so I need to find a way to switch 6
    different resistors into the circuit from the output pins of a PUC uC
    without effecting the circuit in any other way.

    Any suggestions?

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  2. How about an analog switch, like a 4066? It clearly depends on the
    current, but if it's just for timing, there isn't much current.

    Also, what's the problem with digital pots?

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  3. John Fields

    John Fields Guest

     
  4. Just looked at the 4066. It looks like both it and a digital pot have to
    much on resistance. I need to go from close to zero to 1520 ohms in
    discrete logarythmic steps of 120, 270, 450, 690 and 1K.

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  5. "John Fields" wrote ,
    Good idea. I had completely forgotten about reed switches. That will work
    perfectly.

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  6. John Fields

    John Fields Guest

     
  7. John Fields

    John Fields Guest

    ---
    Aaarghhh!!!
    __ __ __
    E1 should be E1 and should go to GND with E2 as shown, and E3 should
    be E3 and go to +V, as shown, so the error is in the logical notation,
    not the connections...

    What next? sighhh...
     
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