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Encoder reading accuracy — Parallax Forums

Encoder reading accuracy

Julian800Julian800 Posts: 31
edited 2010-05-17 00:31 in Propeller 1
Hi All,
I am using Quadrature Encoder object from OBJEX. I use it link to a Auagro HEDL 5645 optical encoder.· I have problem of reading accurate··value. There is about 0.3% to -0.3% different of reading.·· Is there any one else use this object?·· what is your result?··· Or onyone could suggest something I could reduce error?

Comments

  • ErNaErNa Posts: 1,787
    edited 2010-04-23 06:07
    HI, I never had any problem with this QE from OBEX. Did you check the signals, are they 90°phase shifted? Do you have a pull up resistor on each signal?
    Ok, there seems to be an integrated driver, so no need for pull ups?

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    Post Edited (ErNa) : 4/23/2010 6:14:23 AM GMT
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2010-04-23 10:11
    Difference between what and what? How are you measuring the error?

    I really can't see how you can quantify the error in this way, the system is digital and it will either work or not, if it doesn't then the error will grow and grow as the encoder is incremental. Errors are more likely to be mechanical or simply a manifestation of the resolution.

    Graham
  • Julian800Julian800 Posts: 31
    edited 2010-04-26 23:13
    Hi thanks for your help ErNa and Graham.
    I use Propeller drive a stepper and read position by using encoder. the reading of drive position and enocder position is not same at all. the encoder reading also change everytime when I repeat same driving distance. Maybe it is singinal problem. I am check this out now. Anyone can suggest anything else could cause my problem?
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2010-04-26 23:18
    The most likely cause of problems is noise on the encoder lines, especially close to motors. Try turning the motors by hand and see if it is more accurate.

    Graham
  • kwinnkwinn Posts: 8,697
    edited 2010-04-27 02:33
    I can think of 2 additional possible problems. The first is that the stepper motor misses making a step, and the second would be using a 1024 line encoder instead of a 1000 line encoder or vice-versa.
  • Julian800Julian800 Posts: 31
    edited 2010-05-17 00:31
    thanks for all your help!!
    I find the problem is reading differencial to ttl. I need make a board to convert differencial to TLL. that is working now.·

    HEDS-55xx/56xx series encoders are widely used in·industrial contol and servo motor.·It is good thing to have prop work with it
    diff_ttl.png
    700 x 334 - 8K
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