I'm starting a new project were i'm trying to build an exoskeleton, and i want to use the delsys EMG sensors to sens my muscle activity. I want to connect the EMG sensor with the arduino but I don't know how. And I don't now the steps of decoding the signal to were it's a useable variable for the arduino platform. I've been searching for a few days now on different websites and forums and i can't really find an answer to my problems. I hope someone can help me.
Thank you in advance, any information helps!
Well if you have been searching for days then you probably know that EMG works on a mV scale, since our muscles only give off a tiny amount of electricity every time the muscles polarize and de-polarize during a contraction. I use Delsys emg a lot for research, both their old wired systems and their new Trigno system that is wireless. The actual construction of an emg is not that difficult, you just need a way to measure the change in electricity between two points, or bi-polar in the world of research. The difficult part is amplifying the emg to levels that can be used. Most EMG systems use a +- 5V analog system that can be hooked up to a data acquisition device, however a major issue is when you use wired EMG the signal is amplified at the box, this means any noise that is introduced into the cable ie: moving around like lifting weights, will cause the noise to be amplified a great amount, therefore making the EMG unusable. I am not sure why you want to know if you are using a muscle, I mean just look at it when working out, you will see the major ones and the deeper smaller ones you can't see, however you would never be able to use EMG to pick those up anyways without very precise placement. If you are interested in learning more about EMG, the delsys site has a great knowledge base that has many parts to it and explains a lot. I wish you luck in your project.
surface EMG (sEMG), you are going to get very gross information about many muscles.
Needle electrodes (ouch) can gain more specific information, but even that has a lot of contamination from other muscles.
thank you for trying to help me out, but i have a few problems still… You’re saying that the EMG signal is amplified at the wired sensor itself before it goes through the output wire? And that causes more noise in the final EMG signal? I don’t get that… isn’t it so that you reduce the noise in the signal by doing that? And what kind of output wire is it?
thank you for the information, but i want to use it on a regular basis so i don't think a needle sensor is the way to go...
It can be amplified at the electrode or at the end of the wire, but in any case it needs to be amplified. I imagine the delsys amplifies the signal for you at the source. From the electrode on the skin, you are getting about +-100 microvolt signals, so this is a challenging aspect. With movement, you will get artifact from movement alone.
Also, you will get muscle firing from just tense muscles, which doesn't necessarily imply movement, and if there was movement you wouldn't know what kind of movement.
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