optical water droplet counter

Discussion in 'The Projects Forum' started by aka07, Jun 17, 2009.

  1. aka07

    Thread Starter New Member

    Dec 18, 2008
    3
    0
    hi,
    i am working on project , that counts the number of droplets of water falling from a burette. I have decided to use a phototransistor as the sensor. I would like to know which source of light( white light / infra red / blue) would be best to use, so that it would cut the light falling on the phototransistor
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    You can modulate the led signal.
    Use a selective filter at the reciever side.
    In this way the surrounded light will be suppressed.

    Greetings,
    Bertus
     
  3. aka07

    Thread Starter New Member

    Dec 18, 2008
    3
    0
    ok , surrounding light is not a problem. i used an infra red led source. When the droplets fall , its not actually blocking the light. I also tested with white light. So i am not getting any change across the sensor.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    Can you use a reflective setup?
    A water droplet is "transparent" but has a possible reflective surface.

    Greetings,
    Bertus
     
  5. aka07

    Thread Starter New Member

    Dec 18, 2008
    3
    0
    thanx , thats a gud idea, let me try it out.
     
  6. mkbutan

    Senior Member

    Sep 30, 2008
    270
    16
    hi
    it can be very simple just adjust one laser (take care of your eye's) pointing on the drop of water.
    and when drop of water fall's down it will glow in red or blue (depend on the light of the laser you use)and then you can count with yous ckt.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,675
    899
    I believe what you seeing is the result of scatter by the drop. Reflection might work, which takes advantage of the scatter from the drop.

    Another option is to reduce the effect of the scatter. Put a light tube over the detector. Use black paper. A few mm in diameter and 25 mm long should work. A drop that causes the beam to scatter will greatly reduce the intensity at the detector.

    John
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I have done this before. If the drops fall through the optical axis, there will be a large change in the output of the phototransistor.

    We probably need to see the schematic to make helpful comments.
     
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