Selection of presence sensor

Discussion in 'The Projects Forum' started by mcamiea, Jun 27, 2016.

  1. mcamiea

    Thread Starter New Member

    Feb 19, 2016
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    1
    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 lightning conditions and the surface of the target. 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 :)
     
  2. wayneh

    Expert

    Sep 9, 2010
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    So detecting whether the water is on or not is not adequate, you need to tell if a human is there whether the water is running or not?

    A load sensor under the floor comes to mind. Probably not an option for your project?
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Is the person allowed to press a button, or otherwise actively co-operate (sing? :) ) to signal their presence?
     
  4. wayneh

    Expert

    Sep 9, 2010
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    I think a standard break-beam detector could detect a person without too much interference from the water. You could set its sensitivity to ignore the water and only trip when the beam is broken for seconds at a time. You might have to use mirrors to route the light path so that the human can't "hide" from it.

    Adding electronics into a shower requires attention to safety.
     
  5. mcamiea

    Thread Starter New Member

    Feb 19, 2016
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    Actually also detecting the presence of the water works, seems I need to play some sounds while taking a shower, this to be trigger automatically and also turn off automatically. A load sensor, makes e think a lot about waterproofing and safety. will check the break-beam detector thanks.
     
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Fiberglass insert showers often allow access to the bottom of the enclosure from an adjacent wall or ceiling below. It should be no trick putting a sensor under the shower base during installation or even after installation if there is access. No water proofing is needed. No shock hazard either (isolated for shower and low voltage).

    John
     
  7. wayneh

    Expert

    Sep 9, 2010
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    If merely detecting the water is acceptable, you could probably use a temperature sensor right on the shower head. There are also moisture detectors, such as used in microwaves.
     
    djsfantasi likes this.
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Ultrasonic - automobile backup sensors run in all temperatures and weather without recalibrating, so the technology is out there somewhere.
    Broken beam - my favorite at this point. Very low electrical power, easy optical/electrical noise immunity, completely insulate with RTV, peel-and-stick installation.

    Concept: A narrow-beam IR LED has a Vf of less than 1.5 V. Powered by a regulated 2.0 V and current limited to 10 mA at say 20 kHz, that's only 10 mW of SELV energy exposure if all insulation disappears. The receiving phototransistor has less than 1 mW available to it. Bandpass filter and detect the 20 kHz, then missing-pulse detect that to determine body presence +/- 10 seconds. Splashing shower water keeps both the transmitter and receiver clear of fog.

    ak
     
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