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Thread: Building an affordable Pressure Sensitive Floor...?

  1. Building an affordable Pressure Sensitive Floor...?

    Hey,

    I'm new here and have a question regards to building my own pressure sensitive floor, akin to this one http://ame2.asu.edu/projects/floor/.

    I hope you can help me out with it.

    I'm an artist and am looking to build one as early as say now, for an exhibition in February of next year.

    I need help from scratch. i have diddly squat for a budget so would need to build a very cheap version. So, I am open to all suggestions.

    The exhibition will involve a large black square composed of soil (roughly 4 x 4m and 200mm in depth) that the general public will walk onto. Beneath the soil patch would lie the pressure sensitive panels. A live image of their movement on the soil will be projected onto a gallery wall. The plan is to have the projection resemble an aerial map of the soil patch, a simple monochrome that is black with white demarcation lines. The sensors would track the imprints and reconfigure the white lines.

    I've attached an image to give you the general gist of the project.

    Sincerely hope you can help.

    Cheers,

    The Omen
    Last edited by The Omen; 12-17-2009 at 08:07 AM.

  2. #2
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    Re: Building an affordable Pressure Sensitive Floor...?

    Welcome to the forum!

    You didn't give us a budget to stay within, so we don't have any kind of factor. Some budgets are just a physical impossibility - others aren't.
    I Void Warranties´┐Ż

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    Re: Building an affordable Pressure Sensitive Floor...?

    Hey Omen,

    Maybe a pressure sensative floor is not the best solution to the problem. I would think that having 20 cm of dirt between a sensor and the thing you are trying to sense would make your resolution so low that it would be sort of useless, or in the least would create a very general idea of what was going on, and would come at a relatively great expence.

    Another idea would be to use video cameras mounted in the ceiling, looking down at the dirt. You could basically program a cheep webcam to look for differences in color and track peoples movement that way...heck you could probably get away with a sub $50 webcam and a borrowed computer.

    Another idea would be to try to find some way to measure the thickness of the dirt in a given area...thus making the dirt itself into the sensor.

    I don't know...I hope this is helpful.

    DB

  4. Re: Building an affordable Pressure Sensitive Floor...?

    Thanks for the response and thanks for the welcome.

    Prior to the flooring, I thought of using GIS software and like you mentioned darkback, to have a camera installed overhead.

    I'm still considering this an option. My main concern is how would the webcam articulate the differences between the imprints on the soil and the human figures. In the image projected, I just want a map of the soil and no human presence...is this possible? How can the webcam, connected to a program, only scan the surface of the soil alone?

    Any thoughts you have, shoot away.

    Thanks again.

  5. Re: Building an affordable Pressure Sensitive Floor...?

    If you use an overhead camera, the sad truth is that you would have to fake it. You might see where people are, and estimate their heading, then just draw footprints/demarcation lines where you think their feet are. Lots of software exists to estimate the 2D location of a human from a camera view - check out sourceforge if you need a library.

    I'm still a little vauge about what sort of resolution you want from the floor. The article you liked was able to discern quantitative pressure at the square millimetre level - do you need this kind of accuracy? Or do you just want to know where a person is standing, +- 30cm?

    Two things are making this difficult - firstly, you want to spend as little as possible, which rules out a lot of options. Secondly, the dirt floor is going to cause a lot of problems with sensors - it will either clog them, or severely reduce their sensitivity.

    Here is my solution - instead of using an overhead camera, why not use an underfloor camera? Take a glass floor and put a thin layer of dirt (mud might be better), and just aim the camera upwards. When a foot presses against the floor, it will part the dirt and show up as a white footprint shape. Assuming you want to project the footprints on the wall, very little processing is now required - just monochrome your image and perhaps increase the contrast.
    http://www.buildtherobot.blogspot.com - for robot builders and enthusiasts

  6. Re: Building an affordable Pressure Sensitive Floor...?

    Thanks badcommand,

    I know it probably sounds a little too vague...apologies.

    The underfloor camera is a great idea, but the amount of soil is a fairly important part of the work. I couldn't reduce it to a thin layer and the actual image of the footprints is not important. Moreover, I'd have to create a pretty high platform to have the cameras beneath the surface. Not something I want to do, as I want to keep the soil as low as possible.

    The resolution is not important.

    I'm basically creating a plot of land and a map of it and want to have that map manipulated by the imprints made by those that tread on the land. I don't want distinguishable footprints relayed back, just something that could track changes to the surface and have that reconfigure the map i've designed.

    Thanks again

  7. Re: Building an affordable Pressure Sensitive Floor...?

    In that case, If you don't think that the camera idea will work, I would head to Dick Smith Electronics/Jaycar/local electronics store and buy a bunch of cheapish push button switches.

    Then, use a hollow square of foam rubber as a spring, and put it on top of a square wooden box frame. Position the push switch just above the top of the wooden part, and then place a tile or square of chip board on top of that so that when a person is standing on the switch, it is in the ON position. Make mabye 36 (6x6) of these, and cover the whole thing in a sheet of plastic, which you can cover in dirt.

    You now have 36 wires which represent individual grid cells, which need to be multiplexed together in some way for a computer to interpret them. I don't have much experience with good multiplexers, but maybe this? Anyway, you can connect your multiplexed signal to your parallel port and write some software which draws the view you want your projector to show.

    That would be the cheapest and simplest option I could imagine (although I think the camera might offer better results if you can get it to work).
    http://www.buildtherobot.blogspot.com - for robot builders and enthusiasts

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    Re: Building an affordable Pressure Sensitive Floor...?

    I just had an idea...it would be sort of cool...but it isn't exactlly your idea...you could mount a camera in the ceiling...and have it track peoples movement...then you could have the video data create a sort of memory buffer of where people had been...So parts of the picture corrrelating to places people had been would change for a short period of time, and then fade...so you would have sort of trailes marking where people were.

    DB

  9. #9

    Re: Building an affordable Pressure Sensitive Floor...?

    Dirt is heavy. You're looking at 3.2 cubic meters of dirt. That over 3,500 kg of material. Detecting the pressure from a foot print above all that material will be challenging. A mechanical switch as proposed by badcommandorfilename could work. You'll need to calculate the k value for your springs which will be proportional to your resolution (number of panels).

    You said that resolution does not matter but it does. What resolution do you require for this project?

    Besides posting your question, what research have you done to this point?

    What technical skills you do have?
    Last edited by MikeG; 12-17-2009 at 07:23 PM.

  10. #10

    Re: Building an affordable Pressure Sensitive Floor...?

    Most importantly, what is your budget?

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