Resistance Detector, control various functions.

Discussion in 'The Projects Forum' started by REBinc, Nov 17, 2009.

  1. REBinc

    Thread Starter New Member

    Nov 17, 2009
    2
    0
    What I would like to do it build is a project that detects a resistance, and then according to that resistance chooses between 4 different functions.

    For example:
    80ohm = lock doors
    150ohm = unlock doors
    240ohm = traction control off
    300 ohm = vcs off

    The problem is I want to use controls on my steering wheel, but it's output is only two leads, that vary in resistance depending on what button is pressed. I originally was going to send 12v accross it, and then use different amperage rating transistors as switches that would only trip according to a certain resistance, but the problem with that is a low resistance will produce a high current that will also trip all the smaller transistors.

    Is there anything out there I can use?
     
  2. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Use an analog to digital converter. The input would be from a voltage divider using one of your resistors as one of the legs. Using a uController like the Arduino you get the converter and enough processing power to decide what to do with the reading.
     
  3. REBinc

    Thread Starter New Member

    Nov 17, 2009
    2
    0
    Thanks, the Ardiuno looks really promising. It will take me a little bit to look over all of it, but I'm sure I'll have more questions.
    This is looking perfect:
    http://arduino.cc/en/Tutorial/AnalogInput

    I ordered two, I'll update once I can mess around with them a little.
     
    Last edited: Nov 18, 2009
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    LM3914, where the resistor network selects between output steps.
     
  5. Dan-O

    Active Member

    Jul 26, 2009
    38
    0
    Ooo, I like the LM3914 idea, cheap, simple and effective.
    The output could drive a transistor and it's good to go.
    I stepped in because of my pushbutton start project. GM uses a nice rocker switch that is 2 different resistance values for the functions.


    I also found this:
    http://www.madhacker.org/carbuttons.htm
     
    Last edited: Nov 21, 2009
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