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I've been testing the EMG sensor below:

http://www.ebay.com/itm/Muscle-Sensor-EKG-EMG-Developemt-Electronics-Module-Interface-Kit-For-Arduino/351850511727?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

During my tests, I could not get any changes in the signal caused by muscle tensions. When all (3 of 3) of the electrodes where disconnected, my Arduino read 1023, the max analog value. When I had them hooked up, the Arduino read values between 30-40. One problem I encountered, was that it didn't say which of the colors (red, green and yellow) should go where. There were linked a user manual from the ebay link, but they were using different colors. Anyways, I tried all of the possible combinations, but I still got the same result; between 30-40, no remarkable changes in value.

Could it be the adjustable gain? Polarization?

If someone has any experience with EMG, or ideas about what might be the problem, please let me know.

Thanks.

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closed as too broad by Turbo J, PeterJ, Voltage Spike, Nick Alexeev Aug 3 '17 at 6:08

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ I would normally recommend trying ECG first - but you circuit does not seem to be safe enough to do so. I see no isolation. Electrode positions matter less than one might think - EMG looks like line noise anyway. \$\endgroup\$ – Turbo J Aug 1 '17 at 10:12
  • \$\begingroup\$ Note that most oscilloscopes have a test signal output of ~1kHz with a few mV signal, which one might be able to use to test this circuit. \$\endgroup\$ – Turbo J Aug 1 '17 at 10:15
  • \$\begingroup\$ @TurboJ So do you think the chip is the issue? Thanks for suggesting ECG, I will take a look at it. \$\endgroup\$ – MrMongoloid Aug 1 '17 at 10:25
  • \$\begingroup\$ @TurboJturbo. There's no safety difference between EGG and EMG. Safe enough for one, safe (or unsafe) enough for the other. \$\endgroup\$ – Scott Seidman Aug 2 '17 at 1:16
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unfortunately, you've purchased a counterfeit version of our Muscle Sensor v3 which we stopped manufacturing over two years ago when we released our new and improved MyoWare Muscle Sensor. http://www.advancertechnologies.com/2016/07/beware-of-counterfeit-sensors.html

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  • \$\begingroup\$ That doesn't help debug this. \$\endgroup\$ – Scott Seidman Aug 2 '17 at 1:08
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My bet is the rectifier, which often needs a small capacitor in the feedback loop. Also, try using the trimpot to turn the gain up. Lastly, this needs two batteries to provide positive an negative power. Is that how you're using it?

Whichever electrode is connected to the ground goes off by itself, and the others go along a muscle. You might be able to figure it out by inspection, or you might need a multimeter.

Frankly, it's a pretty poor design trying to do the whole amplification with one instrumentation amp.

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