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Selection of presence sensor

Discussion in 'Sensors and Actuators' started by mcamiea, Jun 27, 2016.

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  1. mcamiea

    mcamiea

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    Jun 27, 2016
    Hi guys.

    For one of my university projects I need to detect the presence of a person in the shower. In order to do that what I have in mind is use a proximity sensor. If the target is in a distance range (let's say 20 to 50 cm) It will assume that the person is in the shower when the distance measure is no longer in this range then it will mean that the person left the shower. I need to detect all the time of the person in the shower (meaning when he/she gets in and then out). I have read a lot of info and forums to properly choose the type of sensor. However I still don't have a clear answer. About the Ultrasonic proximity sensors I know that they are cheap and more accurate by it can be affected by Temperature, humidity and some ambient noise, all of them which happen in a shower. The other option an Infrared one gets affected by lighting conditions and the surface of the target, and it doesn't have a linear output. The last option I checked is a PIR sensor I know it senses Temperature of the target, but I don't know if it will be affected by the running hot water and also is more expensive. In general, I don't know how the running hot water will affect the detection of the person in shower. Also,so again I don't know how this will work. Sorry for the huge amount of questions, I am a little bit confuse with all the factors to have in mind. I am hoping someone out there can help a lost newbie like me and give me a suggestion. Thanks a lot :)
     
    Last edited by a moderator: Jun 28, 2016
  2. BobK

    BobK

    7,682
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    Jan 5, 2010
    I think interrupting a beam would be the best solution. You need an IR source on one side and a detector on the other side. Depending on how wide the shower is, multiple ones are probably needed.

    Bob
     
  3. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    A PIR sensor is insensitive to environmental temperature changes and should work well embedded in a shower wall. You should do some research on exactly how a PIR sensor works and why that previous statement is true. You are attending a university, are you not? They are supposed to teach you how to do research there.
     
    davenn likes this.
  4. mcamiea

    mcamiea

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    Jun 27, 2016
    Yes I am researching, had some doubts wanted more suggestions. thanks
     
  5. mcamiea

    mcamiea

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    Jun 27, 2016
    That's a good suggestion I didn't think of before, will check it, thanks
     
  6. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    A lot of public toilets in the USA have PIR sensors mounted in the wall behind the toilet. They "arm" themselves when someone approaches and then flush the toilet when you move away from the sensor. For a shower, you would want to increase the sensitivity, and perhaps fiddle with the IR Fresnel lenses, to extend the range to the width of the shower. Some public restrooms have PIR light switches. These seem to have a much larger range of detection than the toilet sensors. You should investigate both types.

    A PIR sensor is actually two IR sensors (typically pyroelectric) behind Fresnel lenses that present two slightly different "views" to the sensors. Anything in the field of view that is above (or below) ambient temperature will create a differential output from the two IR sensors if the object moves. So, in a shower, you also need a time-delay function after the PIR first detects motion (presence) in the shower before it "decides" based on not sensing any motion that the shower has been vacated.

    If you want something a little more reliable, I would suggest an IR/visible wavelength sensitive video camera with an image processor to do frame-to-frame image comparisons. These are available off-the-shelf for security monitoring applications. However, you might encounter some resistance (human, not electrical) in getting such a system installed in a shower. :D
     
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