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detecting running persons — Parallax Forums

detecting running persons

stefstef Posts: 173
edited 2010-08-06 07:55 in Propeller 1
Hi all

I 'm starting on a new project where I 'm placed with the following problem.

I need to detekt a running person from normal walking persons. I have mechanicaly a coridore where everyone have to walk throug. I can place 5 IR beam sensors in that coridor on a strait horizontal line 50 cm from each other.

My questions now.

Is a propeller fast enouf to detekt the pulses from the sensors when somebody is walking true the coridore and can I make the differance between walking and running?
I found some beam sensors from omron where I get a responce time below 2 ms. They are open collector output and powerd on 12 V DC. How do I safly connect them to the propeller with minimal electronic material between and fasted reaktion.?

Any comment is welcome on this topic.

Stef

Comments

  • LeonLeon Posts: 7,620
    edited 2010-08-03 10:58
    I'd use accelerometers in the floor.

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    Leon Heller
    Amateur radio callsign: G1HSM
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2010-08-03 11:02
    The propeller is fast enough I am sure. How do you intend to use the sensors? Are they range sensors? Break beam type stuff will not work in crowds.

    Graham
  • LeonLeon Posts: 7,620
    edited 2010-08-03 11:15
    I used to work for Irisys:

    www.irisys.co.uk

    and designed the hardware and ported the software for their first commercial people counter. That could be reprogrammed to detect the speed of individual persons, even in a crowd. Development costs would be quite high, though.

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    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 8/3/2010 11:21:50 AM GMT
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2010-08-03 11:36
    Just a thought, an optical mouse sensor uses optical flow for detection so in theory you might be able to use it to detect the motion of people, it would probably need a different lens however. You can get them out of mice but also buy them as modules from digikey and the like.

    Graham
  • stefstef Posts: 173
    edited 2010-08-03 11:51
    Hi

    Leon
    I kwnow the irisys product. I used them already I some other projects. They are good but to expensive for this project.
    What do you mean by "accelerometers"? Can you give me an example?

    Graham
    They are beam type sensors. I know that it can not detect when croud is passing (more than One person at the thime) That is not an issue. It is mechanicly constructed that it is persone by personen that neet to pass. So that is not an issue.


    Is thier somebody that knows how to connect the open collector to the propeller. Thake in attention the higer voltage of the sensor. I think that will bring the open collector also to the wrong level. I can chouse between NPN or PNP.

    Stef
  • LeonLeon Posts: 7,620
    edited 2010-08-03 12:15
    Devices like the Freescale MMA7455L, to detect footsteps.

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    Leon Heller
    Amateur radio callsign: G1HSM
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2010-08-03 14:29
    Stef,

    In that case you should have no problems, compared to the speed of the propeller the speed of mere humans is nothing, you could build something to detect the speed of bullets with the prop.

    Which open collector are you referring to? If the output of the sensor is open collect then you just need to attach a pull up to 3v and connect straight to the prop. Remember an open collector just pulls the collector down to ground when switched and nothing else.

    Graham
  • stefstef Posts: 173
    edited 2010-08-05 20:35
    Thanks graham

    I will try it out.

    stef
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-08-05 21:27
    Smear the floor of the corridor with grease. The running person is the one that keeps falling over. He/she will be the one that is longer, and less tall.

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    Why did I think a new, more challenging, job was a good idea ??
  • HughHugh Posts: 362
    edited 2010-08-06 07:32
    If you don't have to use the PIR detectors, I would have thought that a doppler radar sensor would be a good solution. They used to be used for automatic door openers, etc., I'm not sure if the Parallax one produces an output other than a 'detect / not detect', but it used to be possible to get ones that produced a frequency proportional to the speed of the object from which reflections were being returned. Highest frequency = fastest object...
  • legoman132legoman132 Posts: 87
    edited 2010-08-06 07:55
    the X-band motion detector (parallax) outputs a square wave with a frequency proportional to the speed of a moving object based on the Doppler shift (is that the right term?) I have one, but I don't know the relation of the output frequency to speed other than faster object=higher frequency.
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