DC compound motor feedback circuit by using optocoupler

Discussion in 'The Projects Forum' started by kajiunn85, Dec 14, 2007.

  1. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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    i m using PIC 16f877 to control the dc motor. The problem tat i face is how to construct a feedback circuit by using optocoupler to gif back to the PIC 16f877. Can someone help me?
     
  2. mrmeval

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    Jun 30, 2006
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  3. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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    thanks....actually i bought the optocoupler oredi. can u tell me how to construct the feedback circuit to send back the frequency to the PIC 16f877 to do comparison?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    There are hundreds of very different optocouplers available. Can you tell us the specific one you have?
     
  5. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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    Plz have a look at the picture tat i upload. The optocoupler tat i use is a U-shape optocoupler which has transmitter and receiver together. If u still cant understand please come to tis website (http://ikalogic.com/tut_closed_loop_spd_ctrl.php). Hopefully u can provide some circuit for me. tqtq
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    Okay, you have a photointerrupter. Who makes it, and what is it's designation? We need to know this to determine the receiver of the device - if it is a phototransistor, or if it is some other device. Not all of these things are alike, so we need to have the part number.
     
  7. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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  8. beenthere

    Retired Moderator

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    Put pins 2 and 4 of the optointerrupter go circuit ground. Calculate a resistor to pass between 20 and 50 milliamps current to pin 1. It will depend on your power source voltage.

    The phototransistor will need a large value pullup resistor. Something like 47K for 5 volts, and 100K for 12. Apply the signal to your Schmidt trigger input, as n the block diagram.
     
  9. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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    tq. but how to built schmitt trigger? n how to build a binary counter? soli to disturb u always
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    You don't have to. You decide on a logic family to use and get logic ic's that perform that function. I think you only need the Schmidt trigger function, as the pulses go back to your microcontroller. It has all the internal counters you might need.
     
  11. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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    thanks again. for the schmitt trigger i found tis component tis morning. so let say after the schmitt trigger i dun wan to connect directly to the PIC. wat i plan to use is binary counter. wat can i do for the hardware for tis counter?
     
  12. beenthere

    Retired Moderator

    Apr 20, 2004
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    Assuming you are going to use something like HCT TTL logic, you can apply the signal to a 74HCT161 counter, or chain several for counts greater than 16. Be lots easier to feed into the PIC, though.
     
  13. kajiunn85

    Thread Starter New Member

    Dec 14, 2007
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    I see. after pass thru the schmitt trigger n binary counter. is there any loss? or the another way to say is does the accuracy will not be so accurate? because for the feedback circuit the most important thing is the accuracy.tq
     
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