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

(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!
Reply to
Joe
Loading thread data ...

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

Reply to
t.hoehler

Tom,

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

Thanks

donald

Reply to
Donald

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