Reflecting IR light

Discussion in 'The Projects Forum' started by odm4286, Dec 14, 2013.

  1. odm4286

    Thread Starter Active Member

    Sep 20, 2009
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    I need a good material that I can stick on a gear that will reflect IR light. I've tried reflective tape and aluminum foil so far and while I got results they didn't reflect enough light back.

    If you haven't guessed already I'm building a tachometer. I'm using a IR LED and a photo diode setup. So Im wondering If there is anything that I can pick up at a home depot that will help me out. Thanks.

    P.S. Im using a PLC analog input and not a microcontroller, my code works fine its just I occasionally count "false positives" when there are changes in ambient light. This is just a learning exercise for work by the way.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    How about a Mirror?
     
  3. #12

    Expert

    Nov 30, 2010
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    A red filter will suppress some of the ambient light changes. Maybe steal one off an old remote IR control for a TV.
     
  4. MikeML

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  5. odm4286

    Thread Starter Active Member

    Sep 20, 2009
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    All good ideas but I'm really looking for something that i can easily buy at the store.
     
  6. MikeML

    AAC Fanatic!

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    Standard retro-reflective (like 3M Highway sign or truck tape) material doesn't work for IR.
     
  7. odm4286

    Thread Starter Active Member

    Sep 20, 2009
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  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    White, glossy paper works fine. White vinyl electrical tape works well too.

    Tachometers are usually well covered to avoid ambient light false positives. Use some heat shrink tubing to shroud the LEDs. Also, the angle of the LEDs must be well matched. Some phototransistors (receivers) and IR emitters have angles as little as 6-degrees. Any misalignment causes missed pulses.
     
  9. MikeML

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    I have a aircraft propeller dynamic balancer which uses an IR reflective pickup to determine the angular position of the prop blade relative to where a weight needs to be added. You stick a small strip of the IR retro tape on the back of the prop blade, and have to run the engine (outside), usually in bright sunlight while balancing the prop.
    The reason IR is used is because there is so much ambient light...
     
  10. odm4286

    Thread Starter Active Member

    Sep 20, 2009
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    Found some aluminum tape today at home depot and it worked great. Thanks for the tips guys
     
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