help to replace tacho generator

Discussion in 'The Projects Forum' started by ss.achary, Oct 28, 2015.

  1. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    I would like to replace an dc motor tachogenerator with encoder... But the motor is controlled by drive which has only tacho input for feed back... So I have to fix an encoder with analog output... Tacho spec: 10v/1000rpm..
     
  2. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    What type of circuit should I use to modify it...
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I assume you have an older DC drive that has a DC tach feedback, an encoder is generally digital, what context are you using the drive in? Simple open loop velocity drive or do want or need to control it with a PID loop etc?
    Max.
     
  4. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    I would like to modify an encoder with analog output similar to tachogenerator... This should work in DC drive that has a DC tach feedback...
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Incidentally DC tach's are no longer used in current positioning drives, there is a single PID loop that is returned to the trajectory planner or control, typically using torque mode rather than velocity mode control.
    So if I understand you correctly, you want to use a DC tach as an encoder of some kind?
    Is this an existing system or are you designing something?
    The full story helps, including any details of present equipment.
    Max.
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    The tachogenerator is output an analog voltage, but the encoder output two phase pulses, so you may need two sets of F to V(the Frequency-to-Voltage converter), those provided two directions as forward and reverse, if you don't need the reverse then you just need one set of F to V.
     
  7. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    WP_20151029_12_36_29_Pro.jpg motor used in our machine
     
  8. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    Above is the drive used
     
  9. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    Please provide me full block diagram for it... Encoder - decoder - up/down counter-f/v converter
     
  10. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    WP_20151029_12_34_28_Pro.jpg motor
     
  11. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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  12. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    WP_20151029_12_35_13_Pro.jpg use this encoder instead of tacho... And connect the output of encoder to the same drive... I need help in replacing it....
     
  13. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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  14. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    wp_ss_20151029_0001.png this is hctl2000 ic can I use this ... How can I make to analog....
     
  15. ScottWang

    Moderator

    Aug 23, 2012
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    You can see the encoder pulse, you have to design a pulse detector for encoder forward and reverse, maybe the output as A = pulse, B = low when the encoder forward, and the output as A = low, B = pulse when the encoder reverse.
    rotary_encoder_phase.jpg
    Source.

    And the output of your block diagram, the output of F/V as two 0~5V, how do you use these two voltages to control the motor?
     
  16. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    Please provide me a alternative method...
     
  17. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    wp_ss_20151029_0002.png can I use this to detect pulse...
     
  18. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I doubt you are going to be able to use that quadrature encoder to input to the drive, you would need to convert to a linear analogue signal.
    Is there any reason you are not using the original tach, if built in and is defective, it will be easier to fit an external DC tach, I have done this in the past.
    Max.
     
  19. ss.achary

    Thread Starter New Member

    Oct 27, 2015
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    Sir the tacho coil is costlier... If I use encoder it would be less cost and easy to fix it in motor...
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Have you tried a small (cheap) DC motor ran as a generator, which is all the tach is anyway, just a refined one, if the original tach was 10v/1krpm then a DC motor with the same voltage should work.
    i.e. 20v motor @2000rpm.
    Most drives have a pot to calibrate the tach to fine tune it.
    Max.
     
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