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Optical Encoders

  1. Apr 19, 2005 #1
    Anyone know an easy way to print a rotary encoder with x number of pulses/revolution? Is there like a program that can easily do this? I probably need a few hundred so it's going to be hard to draw them by hand.

    Thanks
     
  2. jcsd
  3. Apr 19, 2005 #2
    You should be able to do this with any cad program. What pattern do you want? How many pulses? If you supplied that I'm sure someone here would whip something up for ya. If you can't afford a CAD package look into some of the free one's. What you'll need to do is draw a single cut out and then polar array that cutout x number of times.

    Do you need these cutout as well? If so then you might want to look into getting these laser cut(I just made a few myself last week--laser cutter made short work of these).

    Are you planning on making simple encoders(a bunch of pulses) or Gray-code encoders:
    http://www.mcmanis.com/chuck/robotics/projects/images/enc-gray.gif

    Anyway, just cad them and good luck.
     
  4. Apr 20, 2005 #3

    FredGarvin

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    It's a piece of cake. If you lay it out with how you want it, I can do it for you.
     
  5. Apr 20, 2005 #4
    There's a fairly inexpensive alternative you might consider. You can take the output of a very simple encoder/tach, and send it to a phased-locked-loop digital frequency multiplier. this can easily be designed to put out virtually any number of count pulses per revolution as are desired - - - and these can drive a counter to give you an encoded output. This is especially useful in a dirty environment such as automotive, where optics might be a problem. (You could use the "gear tooth" type sensors like those on ABS systems.)

    By the way, does anyone know who Today produces those sensors? In the past, if I recall it was a company with a name like "SK".

    KM
     
  6. Apr 21, 2005 #5
    I need a rotary encoder that's 200 pulses/revolution. Just 200 dark lines coming from the center and going to the edge of the circle. I'd really appreciate it if anyone can make one for me and copy/paste it on paint or something I can open and send it to gshoukry@mix.wvu.edu

    Thanks!
     
  7. Apr 22, 2005 #6

    FredGarvin

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    What diameter?
     
  8. Apr 22, 2005 #7
    Diameter = 20 cm or 7.87 inches.

    Thanks again!
     
  9. Apr 22, 2005 #8

    FredGarvin

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    As a first try, see if this will work for you. I didn't put any numbers on it and the lines got so close together towards the center that I took them out to make it more legible. Tell me what you think.
     
    Last edited: Mar 11, 2006
  10. Apr 22, 2005 #9
    This is awesome! thanks man. I gotta learn how to do that one day.
     
  11. Apr 22, 2005 #10

    FredGarvin

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    It's a piece of cake. Anytime.

    I'll waive my normal consulting fees (just this once).
     
  12. Apr 25, 2005 #11
    Hey Fred, do you think you could make the lines thicker? I need them to be just a little more than a mm on the edges, like 1.2-1.3 mm on the edges. You think you can do that? I'd really appreciate it because the sensor we have doesn't read those lines. It would be very nice if you can make the lines' thickness equal to the spacing thickness.

    Thanks!
     
  13. Apr 26, 2005 #12

    FredGarvin

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    Give these a try. Let me know if you want thicker lines or if I went too far. I think #3 is getting too thick. I don't think I'd be able to make the lines and spaces equal in thickness without changing how I did the encoder. Try it, if it doesn't work for you then I will change it around. I know what you're going through getting one to read. Been there. Done that. Got the t-shirt. Aggrivating, isn't it?
     
    Last edited: Mar 11, 2006
  14. Apr 27, 2005 #13
    It works! I didn't try #2 because I don't want the sensor to skip counts (it skips when the lines are small and the encoder is moving fast).But # 3 works very well. Right now that I know the sensor can read those lines, the more pulses I have, the more accurate the scale will be. So, you think you can make a few encoders with the thickness of #3 but with 250/300/350/and 400 pulses per revolution? If it's any trouble at all, forget about it. With the 200 pulses we have we should be able to weigh stuff exactly within 10% of actual weight which is what the instructor wants (ignoring friction and everything). So, 200 works good on paper but I don't know how good it will be when we actually try it. Any encoders with more lines would be awesome though.

    Thanks :biggrin:
     
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