Air sensing switch

Discussion in 'The Projects Forum' started by bowlingo, Feb 25, 2012.

  1. bowlingo

    Thread Starter Member

    Jun 29, 2011
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  2. BSomer

    Member

    Dec 28, 2011
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    Perhaps something like a differential pressure switch will work. It will sense a difference in pressure between two locations, i.e. the difference between the inside of an air duct and the outside of the duct. They are commonly used in commercial buildings for control of large HVAC units.
    I guess what we would need to know is what your application of the "air flow" is and what kinds of air volume you are trying to detect. A differential switch can detect low volumes of air movement if that is what you need.
     
  3. bowlingo

    Thread Starter Member

    Jun 29, 2011
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    I am planning on putting it directly on the outlet and dont want to restrict the flow...as of the spec

    PUMP SPEC. 240 Volt 60 Ltrs / min 4.35 psi
     
  4. BSomer

    Member

    Dec 28, 2011
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    So you do not want something like this correct...
    http://www.dwyer-inst.com/Product/Pressure/SinglePressure/Switches/SeriesAPS-AVS
    This device just switches when there is pressure present.

    Where as this device will switch when there is a certain amount of air flowing by...
    http://www.dwyer-inst.com/Product/AirVelocity/AirFlow/Switches/SeriesAVFS/Specs
    An actual air flow switch may not be very inexpensive, such as the one I linked to which is $215 USD. There are other types that have a paddle which sticks into the pipe or duct. These, however, may restrict the air flow a little in your case.

    Then there are these...
    http://www.dwyer-inst.com/Product/Pressure/DifferentialPressure/Switches
    They are like I initially described, measuring a difference in pressure.

    I just googled air flow, air pressure, and differential pressure switches. I was familiar with Dwyer because I used to use their products when I worked for a company that did HVAC control systems. What it comes down to is if you just want to know if there is pressure in you line or actual flow. Any of the above should work.
     
  5. bowlingo

    Thread Starter Member

    Jun 29, 2011
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    so it dosent seem these are very common such as float, flow switches etc?
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    For the air, you could use automotive technology. They use a bridge of thermistors. One in the air flow and the other in close proximity but shielded from the flow.
     
  7. bowlingo

    Thread Starter Member

    Jun 29, 2011
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