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Human Detector using Propeller? — Parallax Forums

Human Detector using Propeller?

joemacjoemac Posts: 9
edited 2013-01-31 13:15 in Propeller 1
I want to start a project that uses a Propeller to function as a "infallible" detector of a Person.

The sensor will be a loop of wire that is 3 foot in diameter. Actually it is a copper wire that has 40 turns
that are taped to make a loop. The idea being the loop is under the floor mat.

So the loop acts as an inductor driven by the Propeller, then by magic the Propeller senses change in the
inductance change caused by a person entering/crossing the loop.

Any ideas? I'll watch this thread for comments, THANKS -Joe

Comments

  • LeonLeon Posts: 7,620
    edited 2012-05-18 09:18
    That technique isn't "infallible"! What will be the change in inductance that you are expecting?
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-18 10:53
    First, when it comes to electronics, the only infallible thing in the universe is potential fallibility.

    I think what Leon is insinuating by his comment is that raw humans (those who are uncooked and not wearing metal in their shoes) are not likely to alter the inductance of a loop in any detectable way using everyday means of creating magnetic fields, etc.

    You might want to look into using Passive Infrared Devices (PIRs). See the following:
    http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/pir/List/0/SortField/4/ProductID/83/Default.aspx
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2012-05-18 13:52
    Haven't tried it, but I have wanted to .... since the average person is roughly 5 to 6 feet tall, calculate the wavelength as if >they< are one half of a dipole antenna standing 5.5feet tall. If they stand on an insulated plate on the floor with an approximate 43MHz signal fed to the plate, a nearby receiver tuned at 43MHz should be able to detect if a person is standing on the plate or not.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-18 14:12
    Beau Schwabe (Parallax) wrote: »
    ... If they stand on an insulated plate ....

    Will that still work even if they're wearing insulated shoes?

    Of course, you might amp up that idea and run the thing at 2.45 GHz and 1000 watts. Then use a thermal sensor and a sound sensor and correlate the thermal reading with scream detection.
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2012-05-18 14:30
    "Will that still work even if they're wearing insulated shoes?" - should, but I don't know for sure
  • Heater.Heater. Posts: 21,230
    edited 2012-05-18 14:36
    Never mind the insulated shoes. Any metalic objects about their person wil confuse the thing.
    Just the other day I caused an airport security fence to beep like hell even if I have nothing "odd" on me resulting in a pat down check.
    It's not so easy.
  • pedwardpedward Posts: 1,642
    edited 2012-05-18 14:38
    Heater. wrote: »
    Never mind the insulated shoes. Any metalic objects about their person wil confuse the thing.
    Just the other day I caused an airport security fence to beep like hell even if I have nothing "odd" on me resulting in a pat down check.
    It's not so easy.

    Ahh, they threw a coin in there so they could get to know you REAL well!
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2012-05-18 21:17
    This is what I was trying to describe.... I think there is potential here that could be used to detect the presence or non-presence of a person standing in a specific location.

    http://www.youtube.com/watch?v=0H22E_f5h6w

    Note: the video loses sync with the audio about half way through but in actuality, the tone could only be heard as I waved my hand over the single loop coil.... The "loop" shorted to itself could be an important factor here because you want the signal to radiate as little as possibly unless it couples into a person standing over it or a hand waiving over it. A single piece of wire would radiate too much like an antenna and defeat the purpose.


    Note:
    The transmitter loop was about 3/4 inch diameter bare wire loop connected to itself after a single loop. A small tail 1/2 inch was connected directly into P0 and layed over on the SBB
    The receiver was about 4 feet away from the transmitter.

    Here was my test code.... Note the shortwave receiver that I have only goes up to 30MHz, so that's what I used. 
    CON

  _CLKMODE = XTAL1 + PLL16X
  _XINFREQ = 5_000_000

OBJ

Hz            : "Synth"

PUB Main

    Hz.Synth("A",0,30_000_000)
    Hz.Synth("B",0,30_001_000)

    repeat
  • jmgjmg Posts: 15,173
    edited 2012-05-18 21:32
    joemac wrote: »
    The sensor will be a loop of wire that is 3 foot in diameter. Actually it is a copper wire that has 40 turns
    that are taped to make a loop. The idea being the loop is under the floor mat.

    So the loop acts as an inductor driven by the Propeller, then by magic the Propeller senses change in the
    inductance change caused by a person entering/crossing the loop.

    That is more likely to work by capacitance, rather than inductance, so it will depend a lot on what is under the floor.

    Since you have a large mat, why not use the cheap-and-cheerful, tried and proven, pressure mat ?
    Or an optical beam, also tried and proven...

    You could work purely capacitive, with a underlay ground plane to remove floor variances.

    See this thread :
    http://forums.parallax.com/showthread.php?140096-Propeller-controlled-Capacitive-Load-Cell
  • g3cwig3cwi Posts: 262
    edited 2012-05-18 23:53
    I would use the prop to connect the alarm circuit to a large red button. Put a label above the button marked "DO NOT PRESS THIS BUTTON". No human could resist. Detector sorted.

    Regards

    Richard
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-05-19 01:41
    1. Just put a notice up saying "DO NOT PUSH THIS BUTTON"

    2, Put out a camera chart, and put a pressure mat in front of it.

    I remember a PCB kit that I bought as a kid, it had a sheet of paper with possible things to make.One of them was a man/woman detector, this was a wein bridge with one arm being a thermister at the focal point of a car headlight reflector (back when they were made of metal). This was to be pointed at the lower legs and detect the heat or not. It wouldn't be much good with these "modern" women who wear trousers (or with Scots men ...)

    Edit D'OH read the last post
  • MicksterMickster Posts: 2,694
    edited 2012-05-19 01:55
    ElectricAye wrote: »

    Of course, you might amp up that idea and run the thing at 2.45 GHz and 1000 watts. Then use a thermal sensor and a sound sensor and correlate the thermal reading with scream detection.

    Great! Coffee all over the damn keyboard and monitor.....LOL

    Actually, though, when are we going to see a Kinect hooked up to a Prop?

    Mickster
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-05-19 03:13
    1000 Watts would take a while for a whole human, unless the "do not ..." button could get them to fall into a smaller metal box, with a rotating floor.
  • Heater.Heater. Posts: 21,230
    edited 2012-05-19 04:06
    You know, there is such a thing as non-destructive testing.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2012-05-19 05:25
    At work we have a set of three 500 Watt 14GHz jokers, and loads of 150 Watt ones.

    Be reasured that the possibilities of more of the Seckshund clan is minimal, now.
  • PropGuy2PropGuy2 Posts: 360
    edited 2013-01-31 13:15
    I did that a few years ago for a company I used to work for. A different concept though, it used "ion mobility" to sniff the human body odor. You can search the Internet to find out how it is done.
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