Modifying a feedback signal

Discussion in 'The Projects Forum' started by 275kv, Nov 3, 2012.

  1. 275kv

    Thread Starter New Member

    Nov 3, 2012
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    0
    Hi,

    I'm trying to workout how I can modify the signal coming from a position sensor to change it's characteristics. I have attached a graph that shows the current output and the output desired. I expect I should be able to achieve this with a a few op amps but have so far been unable to work it out. Any ideas?
     
    Last edited: Nov 3, 2012
  2. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    What's your position sensor? (info,link)
    What you have the circuit?
    What is the problem of that circuit?
     
  3. 275kv

    Thread Starter New Member

    Nov 3, 2012
    3
    0
    The sensor is part of a throttle body on a diesel engine, it's sealed unit. My goal is to design an interface unit that will modify the V returned to the ECU (as shown int the graph) so that the throttle body will respond differently - just between 1v and 4v as the graph shows. As yet there is no circuit, just the idea, hence my questions. Ideally I would like to build a circuit that has Vin = Sensor V and a Vout = Modified Output
     
  4. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    You have to separate the voltages to 4 sections, and detect them.
    1. To keep the original input voltage when less 1V from the position 0% to 20%.
    2. To keep the voltage at 1V from the position 20% to 60%.
    3. The voltage increasing from 1V to 4V from the position 60% to 80%, this section should be have a base value to do the adjust from 1V to 4V, maybe it is a some kind of rising rate.
    4. To keep the original input voltage from the position 80% to 100%.

    When you get the 4 parts as above, and then assembly them become the output, that is your modified output voltage.
     
  5. 275kv

    Thread Starter New Member

    Nov 3, 2012
    3
    0
    Thanks - almost there. What do I use to choose the lower of two inputs and then pass this voltage to the output. i.e. if A= 2v and B = 4v output should be 2v, if A=4v and B=3V then the output should be 3V.
     
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