is opto-isolator suitable to connect 3.3V PWM microcontroller to 10V LED driver?

Discussion in 'Embedded Systems and Microcontrollers' started by cadet63, Jun 26, 2013.

  1. cadet63

    Thread Starter New Member

    Apr 14, 2013
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    0
    Hopefully I'm asking the right question in the Title. I'm a beginner with electronics, so I maybe could state it better.

    Here's the more detailed explanation:

    I have an LED driver that has two wires marked PWM + and -. The manufacturer suggests 0-10V. I'd like to control the LED driver with my Raspberry Pi, which, as I understand it, can send a hardware PWM signal from 0-3.3V.

    So my question is: what's the best way to do this? Someone on the RPi forums suggested I use an opto-isolator to isolate the circuits. Can anyone concur with this, or have other suggestions?

    I think at this point, just buying an IC opto-isolator (if that's the best solutions) that I can plug into the RPi on one side, and the driver on the other would be ideal. Does anyone know where I might find something like this that fits the bill?

    thanks in advance for any tips/help.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Welcome to AAC and congratulations on a perfect first post with a perfect title.
    We like to see a title that is descriptive followed by a good explanation of what you are attempting to do.

    Yes, the RPi can send a 0-3V PWM signal. You might be able to connect the output of the RPi directly to the LED driver. However, as you have been told, using an optoisolator is a good idea because you can have the RPi electrically isolated from the LED driver and this gives the RPi some protection from nasty signals which might appear on the LED driver.

    The 4N33 optoisolator is a very common device:

    http://www.digikey.com/product-detail/en/4N33/4N33VS-ND/1738521
     
  3. cadet63

    Thread Starter New Member

    Apr 14, 2013
    3
    0
    Thanks for the URL to a suitable device!

    Looking at the datasheet, I'm feeling a little in over my head; could someone give some quick tips on how to wire this thing, or direct me to the relevant info in the datasheet?

    Also, just for my own enlightenment, is it the Output section of the Maximum Ratings table that indicates that I can use 3.3V on one end, and 10V on the other? It seems I should connect the RPi to the Emitter side, and the driver to the Collector side, but I don't really know how to read these specs.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Here is an example of a RPi driving a motor via an optoisolator. You can modify this to suit your current requirements.

    [​IMG]
     
  5. cadet63

    Thread Starter New Member

    Apr 14, 2013
    3
    0
    thank you!
     
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