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Thread: Servo motor control : pc parallel port

  1. #31

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    ohh sorry
    The password is "pictures"
    I will edit the post after you see the password

    Also, if possible have a look at my other post "making a motor lift on its on"

    I cant get any headway in that

  2. #32
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    hi hi

    Its surprising that you got any kind of voltage, from those wires. Looking at your pictures, it looks like you have a gray code encoder disc.

    What you have, is a slip ring. 3 slip rings in fact. But it is not clear from the picture if the 3rd ring is coded. In simple words, its a rotary encoder. If the code is gray or not, i dont know, but it looks very much like a 3 bit gray code disk.

    What happens is, when the shaft moves, the shaft gets contact with the track - and the track is connected to the wires. These are simple switches. Google for gray code rotary encoders, and you will know what i mean.

    It would have been better if the pictures shows the connection of wires to the disk. chose a different angle. But i guess, you must be able to make out how to go from here. Try thinking, rather than asking every little thing here. NO offence, but its a better way to learn.



    .... I didnt do it ! ....

  3. #33

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    http://s686.photobucket.com/albums/v...t=CIMG2625.jpg

    Have a look at this
    This is only a rough sketch. Please ignore the lighter lines
    W goes to white wire, b to black and r to red
    However, the projections on the outer and inner rings are somewhat placed like this only. no symmetry

    I guess it is some encoding after all
    Also, the part that moves on the rings has been marked red to show that it moves on the projections but not on the rings i.e its width is such

    My theory is that the part that moves on the surface when comes in contact with the projections makes connection between the inner and middle and the outer and the middle

    This is some kind of signal for the position. Maybe it is gray code as allbits described

  4. #34
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    its no gray code, its just a custom made encoder. (for that particular appication from which you ripped off the motor.)

    It would have saved a lot of time if you have posted things in detail in one of the previous posts..

    If you are doing your graduation, you must be having enough common sense to make out how this thing works. !!!

    If not, you should be trying to build it(common sense), before venturing into anything else.

    Just look at the contacts and THINK what happens when the shatf rotates.

    It will solve all the mysteries surrounding it.
    .... I didnt do it ! ....

  5. #35

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    forgive me for my folly
    I only realised yesterday that a camera could never convey the full thing that I see

    Again, please forgive me for making this 33 post s long!!! I could have wrapped it up in 3 posts. I am really sorry

    What I inferred, I conveyed in my last post. I verified by an ohmeter and it confirms my theory

    But, what I still dont get is how to read resistances/voltage/current fluctuations using an electronic circuit??? If I take the middle ring as ground, then it may be possible to take resistance readings but can they be used to infer position

    Also, as you say it is custom made, can it tell the location cause i think it cant tell it exactly

    Yes it can tell when one complete rotation takes place using the inner most ring but not the exact location. So, it could tell you the speed at least (considering no angular acceleration)

    How can we take input from the inner ring??

    Again I apologise for troubling you.
    Being a complete novice, I look upto you people to understand things better

  6. #36
    Administrator T-1000 rao's Avatar
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    Praneeth

    just give it 5 volts. that will give 5v pulses at times, make your micro read the pulses, make it calculate the time between two pulses. Simple.

    Rao

  7. #37

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    @rao
    Thanks for the reply

    Can you give me some links regarding reading the voltage/current reading using pc parallel port

    Also, I am planning t buy the arduino/freeduino board offerred by roboticsindia. Would it help in this regard????

  8. #38
    Administrator T-1000 rao's Avatar
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    If you look through the topics link in the navigation bar, you will find awesome parallel port tutorials written by gerry.

    Yes the board will help you obviously, as a matter of fact you will have an easier time doing ADC and other compare operations with it.

    Rao

  9. #39

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    Thanks for the help
    This is just for a formal closure of the topic as I have been able to do what i wanted to

    I connected the red and white wires to two input pins on the parallel port(pin 11 and 12) and the black one to ground

    And the motor wires i connected to parallel port using l293d. And using timer in VB, i am able to determine the rpm and to some accuracy the position of the rotor. that is quite useless at high rpms but somewhat useful at low rpms

    And in the process, I fried two parallel port pins which are now grounded

    Again thanks to allbits,rao and all

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