Motion sensor

Discussion in 'General Electronics Chat' started by woodguy60, Mar 28, 2015.

  1. woodguy60

    Thread Starter New Member

    Sep 21, 2011
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    Hi I own a cnc woodworking machine the spindle on this machine is water cooled.
    it uses a 1/2 inch water line. In this line i have inserted a plastic paddle fixture that turns when the water
    flows. this is so i will know if the pump is working.
    I need to go one step further with this.
    i would like to add a sensor that will operate an alarm it the paddle stop moving.
    looking for advise how to go about this is there a ready made unit i can purchase or a simple circuit
    i can make.
    thanks Paul
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    You could add either an optical or magnetic sensor to the shaft of the paddle so that a steady stream of pulses are produced when the paddle is turning, you then use these pulses to reset a timer. if the rotation stops, so will the reset pulses and the timer will expire, triggering an alarm.

    A 555 monostable circuit is all you need.
     
    Last edited: Mar 28, 2015
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  3. Brownout

    Well-Known Member

    Jan 10, 2012
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    Is there an electrical output from the paddle, or is it just something you look at?
     
  4. cmartinez

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    Jan 17, 2007
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    I've done that before... use a 555 circuit configured as a "missing pulse detector", and install a magnet at the paddle, and a hall effect sensor on the outside.
     
  5. cmartinez

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    Jan 17, 2007
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    just noticed your post... shame on my reading skills...
    Anyway... I just wanted to add that there are industrial paddles out there that already deliver the pulses that you need.
     
  6. woodguy60

    Thread Starter New Member

    Sep 21, 2011
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    its not possible to add anything to the paddle as its inclosed with just an inlet and outlet.
    where can i find one of these industrial paddles. no electrical output from the paddle just something i look at.
    thanks
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If it has an external shaft that you can attach or glue a miniature button magnet, and then use one of the Honeywell SS400 series of unipolar sensors.
    Max.
     
  8. cmartinez

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    Jan 17, 2007
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    Then you could use an optical sensor... just light up the paddle real well with a white LED to produce a strong contrast of light and shadow.
     
  9. woodguy60

    Thread Starter New Member

    Sep 21, 2011
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    yes i like the idea of the optical sensor now how do i go from there lots of this is a bit over my head.
    is there some place i can purchase what i need like on ebay? or someplace else. i live in the caribbean
    thanks pau
     
  10. cmartinez

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    How familiar are you with building electronic circuits?
     
  11. woodguy60

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    Sep 21, 2011
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    i have some idea of building circuits once its straight forward plus i have testing equipment
     
  12. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Can you post a couple of photos of your sensor, just to give us a feel for the surfaces and room around it?

    ak
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you use optical, they are usually miniature retro-reflective tape style. They are about the size of the end of a pencil eraser.
    I should have a part No around here some where, as I have used them in the past.
    Max.
     
  14. cmartinez

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    Jan 17, 2007
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    And if you do go for optical, you'll need to either shroud from external light that will probably won't let you see the paddle anymore, or use a filtered infrared type of sensor and emitter.
     
  15. woodguy60

    Thread Starter New Member

    Sep 21, 2011
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    photo i can make a support close to the paddle
     
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  16. ian field

    Distinguished Member

    Oct 27, 2012
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    You can buy off the shelf reflective sensors for this type of application, they use IR to reduce the effects of ambient light.

    If even that doesn't beat the ambient light, I'd check out firms like Omron to see if they offer a similar sort of thing, but with pulse modulated IR beam and filtered detector.
     
  17. Brownout

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    Jan 10, 2012
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    I would consider a lazer diode that shines across the blades, offset from the center so that the beam gets interrupted by the blade as it passes thru the beam.
     
  18. tracecom

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  19. cmartinez

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    You know what.... it would be a lot easier if you posted a picture of your wheel paddle
     
  20. tracecom

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    See post 15.
     
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