Signal condition circuit

Discussion in 'The Projects Forum' started by 1:1, Feb 23, 2007.

  1. 1:1

    Thread Starter Member

    Jan 25, 2007
    27
    0
    Hai dear forum member,

    I'm current design a scale and shifting circuit use for positioning sensing.
    My sensor is a 10K linear pot(potentiometer) connect to 5v & Gnd. Ideally this linear pot output will be Vref/2 (mean the position is balance). <Vref/2 mean the pole fall to the left, >Vref/2 mean the pole fall to the right.

    The linear pot output is connect to microcontroller A/D (10bits). The microcntroller +Vref & -Vref is 5volt and GND, so I want the controller read the signal such as condition set below.

    *Input to microcontroller is swing between 0~5volt
    Output from linear pot is 0~5 volt as well, but Vref/2 is equal to 0volt input to the microcontroller.*

    I have using a differential op-amp to implement the shifting, an additional offset voltage (Vref/2) is use to compensate the linear pot output (because Vref/2 is mean the pole is balance,so 0 volt will input to the microcontroller represent no error occur). But adding this offset voltage will cause the input to the microcontroller swing between -2.5v ~ +2.5 v. *Note, i need the voltage into microcntroller swing within 0~5 volt (+Vref & -Vref).

    Could any one give me some ideal to solve this problem?
    I was think about is it possible do it in software instead of alter the hardware.

    Thank in Advance!!
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Isn't it possible to leave the input hardware alone and handle the digital value in the software as a signed 10-bit number with the most significant bit used to indicate the sign of the value above and below the Vin/2?

    hgmjr
     
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Without a graphic schematic I can't tell what you're doing.

    This has a method for using a potentiometer
    http://www.seattlerobotics.org/encoder/jul97/basics.html

     
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