Determine number of people in a room

Discussion in 'The Projects Forum' started by praondevou, Jul 11, 2011.

  1. praondevou

    Thread Starter AAC Fanatic!

    Jul 9, 2011
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    Ok, here is what I want to do. No I actually did, but I want to know if someone has a different idea on how to approach this.

    I want to know if a person ( or more than one) is present in a room and when there is one I'd turn on the light.
    I did this a few years ago with a light beam made out of one IR transmitter (the modulated one for IR controls) two IR receivers, a few logic ICs and a triac etc. Not very difficult, I could determine the direction of the person passing through the beam and count the number of people.

    However, this whole thing needs a power supply at a place where I do not always have a power outlet nearby and it has more wiring than I want to.

    Does anybody have experience with a system that senses the presence of a person?

    I do not want to use IR Motion sensors, because the person is not necessarily moving. The person can also be hidden behind some furniture.
    The system should also still work when I moved around a chair for example. So simple capacitive proximity sensors/loops might not work.

    Only a human beings presence should be detected.
    I am not asking for schematics here, just ideas.

    Thanks for any feedback
     
  2. TBayBoy

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    May 25, 2011
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    How about some kind of sound sensor, if you remove heat and motion, there really isn't much left to detect.
     
  3. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Sure there is! Carbon Dioxide, water vapor, heart beat...not that any of this would be easy!
     
  4. TBayBoy

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    May 25, 2011
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    CO2 output varies person to person, so I don't think you can determine number of people from that, water vapor would be weather and ventilation dependent.

    How about a pressure sensor field across the door floor and determine direction of movement by foot falls?
     
  5. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Don't be so quick to dismiss ideas...you'd be surprised how many things I have done that others thought were impossible. All ideas are good, at least to get the brain juices flowing.

    Here's another one: an XBox Kinect.
     
  6. TBayBoy

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    May 25, 2011
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    Correct, I was pointing out pitfalls, to determine the number of people, I feel we can't use items that would require unique calibration. There are pitfalls in my floor sensor idea, what would happen for a wheel chair?

    I would love to hear about your projects, anywhere I can learn I'm game, start a thread, I'll be an avid reader, I might even ask a question or two.
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Traffic lights are sometimes controlled by microwave transmitter devices. They memorize an echo pattern and store it, then create an output trigger when the echo signature is different than the remembered one. Changes which occur to the echo and which remain in the new state for a sufficient period of time are submitted to memory as a 'new' pattern. This allows the device to adapt to new environments yet still detect motion.
     
  8. praondevou

    Thread Starter AAC Fanatic!

    Jul 9, 2011
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    Wow, I liked all of your ideas :D

    Just to be sure I made myself clear. The real number of persons is not important. As long as there is more than 0 I want to leave the lights / music / whatever on.

    CO2 - the change occurs too slow I imagine.
    (Ultra) sound - I thought about that, but then, if I leave a window open or a chair displaced, that would change the sound pattern too
    Microwave - maybe a good idea, there is only one difference, cars will reflect MW, so the change in echo pattern is probably substantial. A human will most likely absorb the energy, this also will change the echo of course, but to what degree?

    I liked the idea with Sound/MW echo, have to do some research on this.

    I understand also, that the device could recalibrate itself after a certain time where there is no change to the echo. But what if I'm reading / watching TV? Or relaxing?

    Also, I don't want the device to be needed to be installed, more like plug it in to a power outlet and it works...

    What about a true heat sensor, like they are using in contactless thermometers, could that be an option ? never worked with one of those...

    thanks for your ideas
     
  9. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    How about a scale devices,large squares,so when people move around there exact
    weight would be counted to decimals and use a detection system to keep varifieing
    that the same weight was moving around,even in wheel chair and average
    food comsumption or in case of retail store a magnetic tag would know added weight
    to named Item.An Inventory check could be run in the process,we are talking about
    smart soft ware Changeing weight would be adjusted for number assigned to Items
    1 and for added items,before leaving some attention could be paid to weight Items.
    Keeping It non-personal for many reasons.I will keep running this thru the patent office,
    you heard It here first. All copy rights protected,under the name of Loosewire for
    Id purposes. I am busy on other sites pursueing this Invention.You have sensor cameras
    that detect movement already,so If if you have bank of cameras working with other
    connecting software that knows the weight in every frame.Any changes with software
    could be processed,so using cameras with sensors might be a way to go
    with other software.Image recognition could be used,that Is available now that may
    work better yet with other high tech software that available.The more I think about
    this process,you now have two people asking questions,could I have some advise
    on what I have purposed. Come on guys,this Is Loosewire asking for Information.
     
    Last edited: Jul 11, 2011
  10. praondevou

    Thread Starter AAC Fanatic!

    Jul 9, 2011
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    Scale devices are definitely a good idea, even moving items around won't be a problem. BUT, I imagine the installation is quite difficult/complex... :confused:
     
  11. KJ6EAD

    Senior Member

    Apr 30, 2011
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    If one were to tile the entire floor of a dance club with strain gauges, very many interesting things could be derived from the data.
     
  12. TBayBoy

    Member

    May 25, 2011
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    you could install a rfid under your skin, then whatever room you were in, you could control anything by proximity.

    :)
     
  13. praondevou

    Thread Starter AAC Fanatic!

    Jul 9, 2011
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    I thought about a passive RFID device. maybe not under my skin, but could be implemented into a bracelet, watch or ring. But it should work for everybody not just the person equipped with a device.

    My best guess would be an expensive thermal imaging camera and a software analyzing the captured image. I think it's possible but I'm not a programmer and these cameras are very expensive....

    So by now we have:
    CO2 - slow reaction time
    ultrasound echo pattern- a possibility, this does exist for car alarms, I think, but there is the question of moved furniture and self-recalibrating
    microwave echo pattern - similar to ultrasound
    rfid - every person has to be equipped with such a device
    thermal imaging - too expensive and difficult to develop
    strain gauge - works but not easy to install
    direction detecting IR light barrier at the doors - works but also not easy to install, maybe if it was wireless, but then how to get power to it??

    Any other ideas?
     
  14. TBayBoy

    Member

    May 25, 2011
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    Many doorways have the light switch beside them, you could pull power off that.
     
  15. KJ6EAD

    Senior Member

    Apr 30, 2011
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    How about good old fashioned low tech turnstyles or rotogates. Count them coming and going.

    [​IMG]
     
  16. steveb

    Senior Member

    Jul 3, 2008
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    Which brings up the next logical questions.

    How do you detect the people that always ask to borrow money, and automatically lock the entrance turnstyle?

    Similarly, how do you detect the pretty women, in order to automatically lock the exit turnstyle?
     
  17. praondevou

    Thread Starter AAC Fanatic!

    Jul 9, 2011
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    That's the next step :D

    As it is for rooms in a house, I think the turnstyle entrance is a bit too bulky ;) Also, my wife wouldn't agree with the pretty women detection. She could reprogram it to a handsome man detection, and then what???
     
  18. praondevou

    Thread Starter AAC Fanatic!

    Jul 9, 2011
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    Yes, I thought of that... Still, best would be not having any external wires. Maybe I can think of something wireless, in this case it only had to transmit power over 1 meter or so.

    I'm always amazed how complex a task can be in electronics if even an animal could be trained to do it...
     
  19. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I loled.

    Roll out some aluminium foil under the carpet and connect to one of those newfangled capacitance sensing switch senors. May only need to recalibrate when you move the furniture.
     
  20. praondevou

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    Jul 9, 2011
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    I don't have a carpet :D

    It should be something easy to install, without making too many modifications/mechanical work.
    I could also think of something like the SICK safety laser scanners, but they are expensive too and also need to be reprogrammed if something in the scanned field has changed.

    There don't seem to be many options... Should be failsafe too, like a normal wall mounted light switch...
     
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