breath/wind sensor?

Discussion in 'The Projects Forum' started by mxabeles, Mar 6, 2010.

  1. mxabeles

    Thread Starter Active Member

    Apr 25, 2009
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    Hi I am working on a project for a client where the viewer blows into "something" and it increases voltage the harder one blows. At first we tried a mic but then the obvious problem is that if you talk into it that as well creates amplitude and we only want the act/pressure of blowing to create data.
    Any suggestions?
    One thing I though of was having a little ball in a tube that is infront of a proximity sensor. When u blow the ball moves up towards the sensor creating data, but that is a little to carnival ride for me and might not even work.
    Let me know,
    -M
     
  2. beenthere

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  3. bertus

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  4. retched

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    You can also use a strain gauge connected to a "sail". You would place the flap (sail) in line in the tube. The breath would cause the flap to bend and the strain gauge would measure the "bending" as a voltage change. Use an OpAmp to boost the voltage to a satisfactory level, and you should be good.

    I have yet to use the new "stick-on" strain gauges, but they are very inexpensive and very easy to implement.

    [ed]
    Bertus, that looks very interesting.
    I was looking it over and it seems it may not work as a breath sensor:
    1000 feet per minute is quite a lot of air. It does say flow rates less than 1000fpm, but it fails to state how much less.

    1000 fpm is about 12 mph.

    [/ed]
     
    Last edited: Mar 6, 2010
  5. BMorse

    Senior Member

    Sep 26, 2009
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    or you can use a small permanent magnet DC motor, if you put some kind of small fan blades on it and blow, the harder you blow the more voltage the motor will put out.....

    Take a small motor from a toy, glue some fins on it from a small fan, place it in a tube, now when you blow in on one end it will spin the fins, and cause the motor to generate power, the more the fans spins, the more power is generated....


    WIND SENSOR1.jpg

    WIND SENSOR2.jpg

    My .02
     
    Last edited: Mar 6, 2010
  6. retched

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    It seemed to me he was trying to measure the pressure. rather than or in addition to the speed. If there is no 'flow through" or if there is a restriction, the propeller will not work accurately. So you may need to use a pressure sensor.

    OP any clarification?

    The ball in tube statement kind of threw me. So its not the speed, Are you trying to make one of those "mouth" mouse? The kind paralyzed people use to operate machines and computers?
     
  7. BMorse

    Senior Member

    Sep 26, 2009
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    From what I gathered, he wanted to measure voltage output .....


    From what I can tell from the ball, basically when the ball gets closer to the proximity sensor it outputs a voltage proportional to the distance the ball had traveled up the tube.... so I don't think pressure is what he is after.... but if it is pressure then I would suggest a piezo sensor at the end of a tube would convert pressure to voltage...... the harder you blow into the tube, the more the sensor would flex putting out voltage proportional to the bend in the sensor....


    B. Morse
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Perhaps the Topic Starter can give a bit more details what is wanted.
    How many volts is he expecting at how many "wind".

    Greetings,
    Bertus
     
  9. retched

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    Have you ever seen those lung exercise devices given to patients?

    Basically its a graduated cylinder with a ping-pong ball inside. At the bottom, a tube is attached to blow into. You have a "green" area where you want to keep the ball by regulating your blow rate. This is to help people who have very labored exhales.

    The inhale then just relax all diaphragm muscles at once instead of slowly. It is like, in weight lifting, curling the weight up then dropping it rather then returning it down slowly.

    This "game" allows the patients to rebuild the muscle and neurological connections that have been taxed from being on a ventilator.

    [​IMG]
     
    Last edited: Mar 6, 2010
  10. mxabeles

    Thread Starter Active Member

    Apr 25, 2009
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    Thanks for all the responses. I basically want the HARDER one blows to increase voltage. In terms of voltage amount 0 - 3v is ideal (I am hooking this up to analogue in of an arduino). Its not about speed, just pressure I guess.
    The breath sensor will be controlling video playback in Jitter. There will be about 4 seperate gates, each opened by a different point on the threshold. Example, user blows medium hard animation 3 starts. User blows VERY hard animation 4 starts, etc.

    Thanks, I will investigate these leads and if other ideas come up please post.
    Best,
    -M
     
  11. retched

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    You can use a floating ball type with hall effect sensors, or microswitches. (If you need it on the cheap) Or there are HVAC parts that convert the pressure into a voltage. ready made. Usually they are 24v, but there is no reason you cant split that twice to get around 0-6v.

    They are used with pneumatic thermostats. The respondent pressure is converted to the voltage to let the control board know the temperature. If you have a 30 story building, the voltage drop would kill the standard thermostat wires signal from the 30th floor to the maintenance room in the basement, so they use pressure in a tube.

    Give it a whirl .
     
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