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Force Sensor Wireless Solution- Academic Project

  1. Dec 14, 2011 #1
    Hi friends,

    I'm an outsider with a management science background looking for a solution into a technical matter I can't resolve by scouring the net. I am working on an academic project that will allow me to track multiple pressure or force points and have that information transmitted wirelessly to my computer in a real cost-effective scalable way.

    For example, there are 100 locations and I want to implant a mini sensor underneath each one (say underneath the carpet). I'm not concerned with the impact having to hit the sensor directly. I just care about if the specific point is occupied or not occupied--if it could determine the weight that would be good too, but mainly I'm just concerned about the occupied vs. not occupied status.

    I have seen these two following products that look promising:
    http://www.futek.com/product.aspx?t=...at=fp&m=ffp350
    http://www.phidgets.com/products.php?product_id=1131.

    These products seem pricey, especially the first one. The second product only seems to be analog and USB. There's also this http://www.loadstarsensors.com/vmchk...-software.html [Broken], which fits the criteria for what would probably work but is again too pricey.

    Any ideas on how I could implement this or other resources I could use? The wireless requirement is integral. I can't really find any overseas vendors either.

    Thank you,

    ForceSensor
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Dec 15, 2011 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    (BTW, your first link didn't work for me -- search returned 0 results)

    One possibility would be Cypress' Wireless USB chips/transceivers:

    http://www.cypress.com/?id=10&source=home_products

    I think you would need to do a small PCB and antenna using their chip/transceiver technology, but it should be a pretty simple PCB.

    How are you planning on powering these wireless modules?
     
    Last edited by a moderator: May 5, 2017
  4. Dec 15, 2011 #3

    AlephZero

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    Homework Helper

    There are two ways you could design this. You could have a separate radio link for each sensor, or all the sensors wired to a single radio link.

    The choice of on/off sensors (basically just switches, as used in simple home security systems) or something that can measure the load or pressure will make a big difference to the system cost.

    If there is no problem about "wires under the carpet" it would be quite feasible to wire up literally hundreds of sensors to a single radio transmitting circuit, that scanned all the sensors in quick sucession (i.e. many scans of all the sensors each second, if you need that sort of speed) with a wireless link to your laptop. You might not find a ready-built system that will do that (except possibly a large scale intruder-detection system) but it wouldn't be hard to design and build the scanning and data collection part using a microcontroller, and interface it to a ready-built radio data link module.

    EDIT - a "lateral thought" just occurred to me. What it you took a standard PC wireless keyboard, and replaced each key switch with one of your sensors...???
     
  5. Dec 15, 2011 #4

    berkeman

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    Staff: Mentor

    Interesting, but how many key rollover do most keyboards have? They need at least 3-key rollover for Ctrl-Alt-Delete, but that may be all that they support...

    Ah, it looks like some "high-end" keyboards do support n-key rollover. But I doubt that the simple wireless ones do.

    http://en.wikipedia.org/wiki/Rollover_(key [Broken])

    I could be wrong about that, though. Still a clever idea. :smile:
     
    Last edited by a moderator: May 5, 2017
  6. Dec 15, 2011 #5
    The keyboard is a brilliant cost-effective idea! I'm impressed by the quality of responses here. I haven't thought of a way to power the modules. It would have to be some long duration yet small battery source, hoping to keep the devices as low powered as possible.

    Another issue with the keyboard is that the wireless range is limited, if I want to monitor these devices remotely. I would need a range greater than 50 feet. Looks like the CyFi low power RF only goes to about 33 feet. Is bouncing the signal off multiple routers feasible?

    I noticed this idea: http://www.engadget.com/2006/11/14/how-to-extend-the-range-of-a-wireless-keyboard-with-a-wifi-anten/

    Seems pretty clunky for what we're going for here.
     
    Last edited by a moderator: May 5, 2017
  7. Dec 16, 2011 #6

    AlephZero

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    I'm getting a picture of an "exercise wheel" for couch potatoes here. You get a room-sized PC keyboard that looks like a carpet, and you type by jumping from key to key. Hey, I just reinvented http://en.wikipedia.org/wiki/Archy_and_Mehitabel

    Maybe I should get Nintendo to market this for the next generation of WII ....
     
  8. Dec 16, 2011 #7
    Sounds like a great idea to me. Doing [shift] character or [ctrl] character may inspire laughing fits among co-workers though.
     
  9. Jan 16, 2012 #8
    Hello,
    You might want to get intounch with Deeter Engineering http://www.deeter.co.uk they do a Wireless sensor system that works with any sensor.
     
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