Help with optoisolators

Discussion in 'General Electronics Chat' started by ktnch, Feb 12, 2013.

  1. ktnch

    Thread Starter New Member

    Jan 19, 2011
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    0
    Need some advice, got an arduino 2560 and looking to isolate the pwm 0-5v feeds, been looking at optoisolators to do this then feed the led drivers pwm from the isolator output again will need to be 0-5v

    is the optoisolator best for this job ? guessing i cant use a simple blocking diode

    cheers folks
    kev
     
  2. ktnch

    Thread Starter New Member

    Jan 19, 2011
    22
    0
    Some optoisolators i have are EL817C And a quad TLP504A
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,022
    3,236
    Opto-isolators can be somewhat slow, depending upon the type. What is the frequency of the PWM?

    Do you need galvanic (ground) isolation?
     
  4. ktnch

    Thread Starter New Member

    Jan 19, 2011
    22
    0
    the std freq from the arduino pins is around 480
    980Hz on 5 and 6, 490Hz on 3, 9, 10, 11)
     
  5. ktnch

    Thread Starter New Member

    Jan 19, 2011
    22
    0
    Sorry just need the arduino isolating from the led drivers had one go faulty and blew the arduino pwm output pin out
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,022
    3,236
    You should be able to use a resistor to isolate the driver sufficiently to prevent a failure from damaging the arduino. What is the driver circuit?
     
  7. ktnch

    Thread Starter New Member

    Jan 19, 2011
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    0
  8. sheldons

    Active Member

    Oct 26, 2011
    616
    101
    You could try this ,you can also add a transistor buffer to drive your opto if needed
     
  9. ktnch

    Thread Starter New Member

    Jan 19, 2011
    22
    0
    Cool cheers, at which point n the circuit does the output attach to the pwm 0-5v to to the led drivers ?, also will this still isolate the arduino from the led drivers incase they go faulty ?
     
  10. crutschow

    Expert

    Mar 14, 2008
    13,022
    3,236
    You should be able to add a resistor in series from the arduino output to the led driver input. Try 1kΩ to start
     
  11. ktnch

    Thread Starter New Member

    Jan 19, 2011
    22
    0
    Shall try that, are diodes any good for one way flow ? or will they simply smooth out the pwm signal

    sorry for all the questions
     
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