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Req: Schematic for BASIC electromyogram (EMG) - biofeedback type device - second request, edited

Discussion in 'Electronic Design' started by [email protected], Feb 17, 2007.

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  1. Guest

    (Second request - edited)

    Seems that a VERY basic EMG device could be constructed with a handful
    of off-the-shelf parts. From browsing the group, I've seen where
    these are often class projects.

    Thanks to the group, I've been given some links to block diagrams, but
    I need more detail - parts values and a wiring diagram.

    Purpose - Determine specific muscle maximum output.
    Input- Standard skin electrode pair.
    Output - LEDs preferred over sound. I visualize a simple string of
    LEDs.
    Requirement - no programmable chips.
    Application - I severed the median and ulnar nerves (and a bunch of
    other stuff) just above the elbow. After a couple surgeries, I've
    gained some motion in my thumb, and I'm trying to exerecise it to the
    max muscle activity level, yet stop before the muscle is
    over-fatigued.

    I've used a commercial unit in the Occupational Therapy clinic, but
    with many bells and whistles that I don't need - LCD display with mmv
    readings, timers, sound options, etc.
    The commercial unit displayed readings of 10 to 60 mmv, depending on
    pad placement and fatigue level. With luck, this will increase, but I
    don't know what normal limits are, and don't expect to get anywhere
    near normal levels - 100 mmv max should be adequate. Changing ranges
    would be a nifty.

    Unit must be cheap - crude, if need be. A simple gazinta / comesouta
    is fine. Lights or meter for indication. On the lines of a science
    fair project would be adequate.

    Seems it could be done with a power supply, amplifier, and LED driver
    chip, or maybe easier. I've got a well stocked junk box. Working
    definition of 'junk box' - 'Term used by electronics hobbyists
    describing that assortment of parts, usually acquired over an extended
    amount of time from numerous sources, with condition ranging from new
    and still in original packaging to new or used and mounted on boards
    or sub-assemblies.' We're not talking about a shoe box here. You
    should ask my wife. :)

    As far as skills, that's changed a tad, which leads to my request.
    I've breadboarded a lot, and made enough basic one-sided circuit
    boards to be comfortable with the process. Now, I call whatever I do
    'therapy', and often recruit family to hold things for a second. :)

    Thanks for the help, and if it can't be done I'll quit bothering the
    group.

    Any suggestions?


    ----
    (previous replies)

    Joe,

    The input circuitry for EMG is very similar to that used for
    EEG and ECG. Basicly a high CMMR, differental amplifier with
    a lot of gain. The difference is in the filtering, and what
    you do with the output. Though in EEG and ECG they are trying
    to filter out the muscle (noise) signal, that you want to
    use.

    I used to work in Biomedical Engineeing at the U of Minnesota
    Hospitals, but would have to dig to come up with a design
    from a "handfull of off-the-shelf parts"...for what I assume
    you want to do cheaply(?). What are your skills electronics?


    Try posting your request over on the newsgroup:

    sci.electronics.design

    and

    Google: EMG circuit schematic

    I got lots of good hits, including:

    http://mxp.physics.umn.edu/s02/Projects/Muscle/Project_Propos
    al.htm

    GO GOPHERS!

    This should do what you need for the front-end. Instead of
    sending the signal to a computer you could try driving an LED
    bar display:

    http://www.national.com/pf/LM/LM3914.html

    You may need to put some signal conditioning circuitry
    between the input and the display, but I'll leave it there
    for others to help.

    As my flight instructor used to say: "Do good work...and have
    fun"

    Ken Moffett
    Scientific Instrumentation
    Macalester College


    --------

    I've designed such devices, but I have to say - you want to be very
    careful
    in hooking yourself (however indirectly) to the power line.
    Especially
    when you talk about getting your parts from a "junk box".

    I'd recommend that you keep power demands low enough that you can run
    on
    a smallish battery.

    Good luck!
     
  2. t.hoehler

    t.hoehler Guest

    Seems that a VERY basic EMG device could be constructed with a handful
    If the OP is still reading this thread, contact me off group, I can supply
    you with some EEG/EMG pickup amplifiers at no charge.
    I have several, would be glad to send you a couple.
    Regards,
    Tom
     
  3. Donald

    Donald Guest

    Tom,

    Would you please let the rest of us know the make and manufacture of
    these "EEG/EMG pickup amplifiers".

    Thanks

    donald
     
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