Impact Sensor Ideas.......

ArchiverArchiver Posts: 46,084
edited 2000-03-15 - 18:22:00 in Microcontrollers
Hi All,

I'm looking to develop a training tool for athletes to wear that could
measure where impacts are sustained (different zones would be fine) and
possibly measure the force of those impacts. My question is: What ideas do
you have for the sensing device(s). Idealy, the sensors would be flexible
and/or soft to comfortable to wear.

All input is appreciated - thanks,

Tim

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-03-12 - 21:24:00
    Tim,

    Look into "piezo resistive" materials. These are soft and flexible. I've
    played with them a little.

    This will get you started:

    http://www.piezo.com/index.html

    http://www.acx.com/index.html

    David
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-13 - 19:19:00
    At 01:03 PM 3/12/00 -0800, Tim and Jo wrote:
    >Hi All,
    >
    > I'm looking to develop a training tool for athletes to wear that could
    >measure where impacts are sustained (different zones would be fine) and
    >possibly measure the force of those impacts. My question is: What ideas do
    >you have for the sensing device(s). Idealy, the sensors would be flexible
    >and/or soft to comfortable to wear.

    Check out Beau Schwabe's site - he did a project that used thin flex foil
    inductors in conjunction with a metal liner and thin foam to measure force
    in foot ware. He measured the change in inductance that occurred as the
    pressure changed.

    dwayne



    Dwayne Reid <dwayner@p...>
    Trinity Electronics Systems Ltd Edmonton, AB, CANADA
    (780) 489-3199 voice (780) 487-6397 fax

    Celebrating 16 years of Engineering Innovation (1984 - 2000)

    * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
    Do NOT send unsolicited commercial email to this email address.
    This message neither grants consent to receive unsolicited
    commercial email nor is intended to solicit commercial email.
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-14 - 03:26:00
    At 12:19 PM 3/13/00 -0700, you wrote:
    >At 01:03 PM 3/12/00 -0800, Tim and Jo wrote:
    >>Hi All,
    >>
    >> I'm looking to develop a training tool for athletes to wear that could
    >>measure where impacts are sustained (different zones would be fine) and
    >>possibly measure the force of those impacts. My question is: What ideas do
    >>you have for the sensing device(s). Idealy, the sensors would be flexible
    >>and/or soft to comfortable to wear.
    >
    >Check out Beau Schwabe's site - he did a project that used thin flex foil
    >inductors in conjunction with a metal liner and thin foam to measure force
    >in foot ware. He measured the change in inductance that occurred as the
    >pressure changed.
    >
    >dwayne
    >
    >
    Thanks for the "plug" Dwayne...
    One thing to watch out for with this design is that only one
    "coil" can be polled at a time, otherwise adjacent coils tend to
    synchronize in oscillation with each other.
    The method used on my webpage works well, allowing a
    coil/inductor to resonate in a simple L-C oscillator configuration,
    usually in the 3-5MHz range with a 10uH to 40uH coil. Using a 4040B
    (12-bit binary counter/divider) the frequency can be divided down to
    an appropriate level that a STAMP or PIC can resolve.
    The circuit shown requires about 40mA (<--If I remember right).
    A new design (patent pending), requires about 100uA and takes approx
    15uS to "read" a single coil value.
    The "Coils" were specially designed and etched on a 2 layer
    flexible circuit board in a "pancake" form, spiraling outward
    occupying an area about the size of a nickel.


    BTW) To Everyone!

    I don't know how much longer my site will be active... I am planning
    on moving to Tucker, GA near the first of April and will be changing
    my internet provider. I will will inform the list when the change
    has been made.
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-14 - 06:49:00
    Thanks for the help guys! Beau, at what address can I find your site?

    Tim

    Original Message
    From: Beau Schwabe <bschwabe@i...>
    To: basicstamps@egroups.com <basicstamps@egroups.com>
    Date: Monday, March 13, 2000 7:26 PM
    Subject: [noparse][[/noparse]basicstamps] Re: Impact Sensor Ideas.......


    >At 12:19 PM 3/13/00 -0700, you wrote:
    >>At 01:03 PM 3/12/00 -0800, Tim and Jo wrote:
    >>>Hi All,
    >>>
    >>> I'm looking to develop a training tool for athletes to wear that
    could
    >>>measure where impacts are sustained (different zones would be fine) and
    >>>possibly measure the force of those impacts. My question is: What ideas
    do
    >>>you have for the sensing device(s). Idealy, the sensors would be
    flexible
    >>>and/or soft to comfortable to wear.
    >>
    >>Check out Beau Schwabe's site - he did a project that used thin flex foil
    >>inductors in conjunction with a metal liner and thin foam to measure force
    >>in foot ware. He measured the change in inductance that occurred as the
    >>pressure changed.
    >>
    >>dwayne
    >>
    >>
    >Thanks for the "plug" Dwayne...
    > One thing to watch out for with this design is that only one
    >"coil" can be polled at a time, otherwise adjacent coils tend to
    >synchronize in oscillation with each other.
    > The method used on my webpage works well, allowing a
    >coil/inductor to resonate in a simple L-C oscillator configuration,
    >usually in the 3-5MHz range with a 10uH to 40uH coil. Using a 4040B
    >(12-bit binary counter/divider) the frequency can be divided down to
    >an appropriate level that a STAMP or PIC can resolve.
    > The circuit shown requires about 40mA (<--If I remember right).
    >A new design (patent pending), requires about 100uA and takes approx
    >15uS to "read" a single coil value.
    > The "Coils" were specially designed and etched on a 2 layer
    >flexible circuit board in a "pancake" form, spiraling outward
    >occupying an area about the size of a nickel.
    >
    >
    >BTW) To Everyone!
    >
    >I don't know how much longer my site will be active... I am planning
    >on moving to Tucker, GA near the first of April and will be changing
    >my internet provider. I will will inform the list when the change
    >has been made.
    >
    >
    >
    >eGroups.com Home: http://www.egroups.com/group/basicstamps/
    >http://www.egroups.com - Simplifying group communications
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-14 - 07:17:00
    At 10:49 PM 3/13/00 -0800, you wrote:

    http://www.ionet.net/~bschwabe/
    http://www.ionet.net/~bschwabe/BasicStampII/0000.html
    http://www.ionet.net/~bschwabe/BasicStampII/Coilread.gif


    > Thanks for the help guys! Beau, at what address can I find your site?
    >
    >Tim
    >
    >>>>Hi All,
    >>>>
    >>>> I'm looking to develop a training tool for athletes to wear that
    >could
    >>>>measure where impacts are sustained (different zones would be fine) and
    >>>>possibly measure the force of those impacts. My question is: What ideas
    >do
    >>>>you have for the sensing device(s). Idealy, the sensors would be
    >flexible
    >>>>and/or soft to comfortable to wear.
    >>>
    >>>Check out Beau Schwabe's site - he did a project that used thin flex foil
    >>>inductors in conjunction with a metal liner and thin foam to measure force
    >>>in foot ware. He measured the change in inductance that occurred as the
    >>>pressure changed.
    >>>
    >>>dwayne
    >>>
    >>>
    >>Thanks for the "plug" Dwayne...
    >> One thing to watch out for with this design is that only one
    >>"coil" can be polled at a time, otherwise adjacent coils tend to
    >>synchronize in oscillation with each other.
    >> The method used on my webpage works well, allowing a
    >>coil/inductor to resonate in a simple L-C oscillator configuration,
    >>usually in the 3-5MHz range with a 10uH to 40uH coil. Using a 4040B
    >>(12-bit binary counter/divider) the frequency can be divided down to
    >>an appropriate level that a STAMP or PIC can resolve.
    >> The circuit shown requires about 40mA (<--If I remember right).
    >>A new design (patent pending), requires about 100uA and takes approx
    >>15uS to "read" a single coil value.
    >> The "Coils" were specially designed and etched on a 2 layer
    >>flexible circuit board in a "pancake" form, spiraling outward
    >>occupying an area about the size of a nickel.
    >>
    >>
    >>BTW) To Everyone!
    >>
    >>I don't know how much longer my site will be active... I am planning
    >>on moving to Tucker, GA near the first of April and will be changing
    >>my internet provider. I will will inform the list when the change
    >>has been made.
    >>
    >>
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-14 - 18:12:00
    > I'm looking to develop a training tool for athletes to wear that could
    >measure where impacts are sustained (different zones would be fine) and
    >possibly measure the force of those impacts. My question is: What ideas do
    >you have for the sensing device(s). Idealy, the sensors would be flexible
    >and/or soft to comfortable to wear.
    >
    >All input is appreciated - thanks,

    So long as you aren't looking for super-accurate, highly repeatable readings
    (I assume you're just looking for registration of impact, and a general
    sense of how hard it was), you can roll your own sensors cheaply and easily.

    Take a sheet of conductive, static-proofing foam (The kind they ship/store
    CMOS ICs in), and sandwich it between two conductive plates, sheets, wires,
    etc. The resistance responds inversely to the amount of pressure being
    applied (low resistance == high pressure). The stiffness of the foam
    determines the pressure range and restitution of your sensor.

    This works well for things such as grip sensors in robotics, where you can
    specify approximate grip strengths to be applied. Accuracy and
    repeatability leave a bit to be desired, but whaddaya want for something you
    can make for free?

    Sorry I took so long to throw in my $0.02...

    -- Pat

    ______________________________________________________
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-14 - 23:35:00
    > I'm looking to develop a training tool for athletes to wear that
    could
    >measure where impacts are sustained (different zones would be fine) and
    >possibly measure the force of those impacts. My question is: What ideas
    do
    >you have for the sensing device(s). Idealy, the sensors would be flexible
    >and/or soft to comfortable to wear.
    >
    >All input is appreciated - thanks,

    Back a few years ago at the WESCON trade show, a company called Tekscan
    (800-248-3669, Boston) was showing off a product called F-SCAN, billed as
    "the most advanced in-shoe foot force and gait analysis system". The
    sensor was a double sheet of polyester, with a pattern of resistive ink and
    conductive paths, in a shape to fit inside a shoe. A ribbon of polyester
    came up the ankle and to about 100 plated contacts, thence to a harness,
    thence to a computer to display pressure as function of location on the
    bottom of the foot. I don't know if they are still in business. Contact
    me off-list with your fax number if you would like me to fax you the PR
    sheet. They were even giving out samples of the in-shoe contact device,
    and also one for dentistry. I kept them, so cool they were.

    There are other companies that make thin pressure sensors out of conductive
    inks. IMRC (520-749-1920 Tucson) made one called the "Prescon". Force
    Imaging (800-348-3240 Chicago) made the "Uniforce". Interlink
    (805-684-2100 Santa Barbara) made an "FSR (force sensing resistor)". All
    dated leads.

    -- Tracy Allen
    Electronically Monitored Ecosystems
    http://www.emesystems.com
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-15 - 02:40:00
    At 06:35 PM 3/14/00 -0500, you wrote:
    >> I'm looking to develop a training tool for athletes to wear that
    >could
    >>measure where impacts are sustained (different zones would be fine) and
    >>possibly measure the force of those impacts. My question is: What ideas
    >do
    >>you have for the sensing device(s). Idealy, the sensors would be flexible
    >>and/or soft to comfortable to wear.
    >>
    >>All input is appreciated - thanks,
    >
    >Back a few years ago at the WESCON trade show, a company called Tekscan
    >(800-248-3669, Boston) was showing off a product called F-SCAN, billed as
    >"the most advanced in-shoe foot force and gait analysis system". The
    >sensor was a double sheet of polyester, with a pattern of resistive ink and
    >conductive paths, in a shape to fit inside a shoe. A ribbon of polyester
    >came up the ankle and to about 100 plated contacts, thence to a harness,
    >thence to a computer to display pressure as function of location on the
    >bottom of the foot. I don't know if they are still in business. Contact
    >me off-list with your fax number if you would like me to fax you the PR
    >sheet. They were even giving out samples of the in-shoe contact device,
    >and also one for dentistry. I kept them, so cool they were.
    >
    >There are other companies that make thin pressure sensors out of conductive
    >inks. IMRC (520-749-1920 Tucson) made one called the "Prescon". Force
    >Imaging (800-348-3240 Chicago) made the "Uniforce". Interlink
    >(805-684-2100 Santa Barbara) made an "FSR (force sensing resistor)". All
    >dated leads.
    >
    > -- Tracy Allen
    > Electronically Monitored Ecosystems
    > http://www.emesystems.com
    >
    Tracy,
    These sensors are "Crap" ...One reason we developed our own sensor
    for the purpose of monitoring pressures inside a prosthetic foot or
    a diabetic foot with the onset of "distal neuropathy" (<-loss of
    feeling in the extremities).

    The FSR's from TEKSCAN will not last long under the SHEER stresses
    inside a shoe, and quickly become "de-laminated". Any deep creases
    and the sensors become saturated. The software allows you to
    "normalize" or "zero-out" the returned values to accommodate for
    any sensor bending, but again, when you do this it severely dulls
    the response and range of the sensor.

    The TEKSCAN sensor is great if you are standing still, but for any
    "real" gait analysis where a patient must walk, the sensors poorly
    survived our study. After $10K+ we quickly learned our lesson the
    hard way.
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-15 - 05:55:00
    Tracy wrote:
    >>Back a few years ago at the WESCON trade show, a company called Tekscan
    >>(800-248-3669, Boston) was showing off a product called F-SCAN, billed as
    >>"the most advanced in-shoe foot force and gait analysis system". The ...
    Beau wrote:
    > These sensors are "Crap" ...One reason we developed our own sensor
    > for the purpose of monitoring pressures inside a prosthetic foot
    or
    > a diabetic foot with the onset of "distal neuropathy" (<-loss of
    > feeling in the extremities).
    >
    > The FSR's from TEKSCAN will not last long under the SHEER stresses
    > inside a shoe, and quickly become "de-laminated". Any deep
    creases
    > and the sensors become saturated. The software allows you to
    > "normalize" or "zero-out" the returned values to accommodate for
    > any sensor bending, but again, when you do this it severely dulls
    > the response and range of the sensor.
    >
    > The TEKSCAN sensor is great if you are standing still, but for any
    > "real" gait analysis where a patient must walk, the sensors poorly
    > survived our study. After $10K+ we quickly learned our lesson the
    > hard way.


    Interesting. That goes to shoe again the difference between concept and
    reality. I can appreciate how these laminates would have a problem with
    shear stress. Tekscan had a patent on the sensor arrays (#4734034)--maybe
    they will find a stickier, more elastic ink, or a more suitable
    application?

    -- Tracy
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-15 - 18:22:00
    I seem to recall a piezo film that when flexed produced a voltage. That may
    be a starting point.


    At 01:03 PM 3/12/00 -0800, you wrote:
    >Hi All,
    >
    > I'm looking to develop a training tool for athletes to wear that could
    >measure where impacts are sustained (different zones would be fine) and
    >possibly measure the force of those impacts. My question is: What ideas do
    >you have for the sensing device(s). Idealy, the sensors would be flexible
    >and/or soft to comfortable to wear.
    >
    >All input is appreciated - thanks,
    >
    >Tim
    >
    >
    >
    >-- Check out your group's private Chat room
    >-- http://www.egroups.com/ChatPage?listName=basicstamps&m=1
    >
    >
    >
    Larry G. Nelson Sr.
    mailto:L.Nelson@i...
    http://www.ultranet.com/~nr
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