optocouple arduino input

Discussion in 'The Projects Forum' started by martinmcc, Sep 14, 2012.

  1. martinmcc

    Thread Starter New Member

    Aug 28, 2012
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    0
    I am trying to read a speed signal from a tractors transmission control unit. Its 3.3v and 1-2khz pulse. I'd like to optocouple it and have a few 4n37 available.

    As I really dont want to screw up the vehicle electronics I'd like to verify what I am planning to do.

    The 4n37 needs a forward current of 10ma so I'll put a 220 ohm resistor in series there.

    On the arduino side can I just use the internal pull up resistor and nothing else to read the opto?

    Is the 4n37 fast enough? Turn on/off time is <10us so I am thinking it will be fine.

    Anything else I need to watch for?
     
  2. martinmcc

    Thread Starter New Member

    Aug 28, 2012
    3
    0
    Actually on rethinking this I think optocoupler is overkill as both will be using same power source and so not really isolated. I think I can feed the pulse straight to arduino inputs.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,750
    759
    Better to use opto, it will help in clamping the ignition noise to a safe level.
     
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