PsyLink

3M Red Dot electrodes

Alex Lao suggested to try some 3M Red Dot electrodes, and so I got me some of the model 2248-50 (he actually suggested model 2660 but I mixed it up.) They are used for ECG patient monitoring, which is close enough, right?

photo of the electrodes

I connected two of them to EX1 and EX2 on an Electrode Module 3.1 and placed them on the flexor digitorum superficialis muscle (where I place the built-in PsyLink electrodes on most of the other pictures/videos too), and placed a third electrode on the radius bone near the wrist, and connected it to a Vref pin of a Power Module 4.2, which therefore acted as a ground electrode. The electrode module is the one from the previous blog post about the MCP6N11-100 instrumentational amplifier (for no good reason - I should have used INA128 for better comparability).

This is what they look like on my skin:

Photo of the electrodes on my skin

I recorded the following signals when pressing different fingers onto the table:

Screenshot of signals

The amplitudes of the wavelets were a little disappointing, but perhaps boosting the gain from 501x to 1001x-2001x would help.

The nice surprise was the specificity of the signals. I only saw signals when I actually used that muscle. Unrelated movements like twisting the wrist sometimes produce strong signals with the built-in PsyLink electrodes, but produced no signal with these. There could be many reasons for that:

It's good to see that it works, and there's clearly a potential, but I'm not blown away either. Next steps could be:

Note that before attaching the electrodes, I did not shave off hair and did not clean off skin oils with alcohol, but at least I was fresh out the shower. Ok, time to end this post, this is getting weird :).