Micro USB electrode options for Muse extra electrode port
paulbrennan
Victoria, Canada
Hi there,
My current setup - which is probably just a short term option - uses the mini USB connector on the Muse with a gold cup electrode. These are not that easy to find, and expensive from the current source ($50 each). Ideally, right now I'd like to be using disposables as long as there are no technical issues.
If there's no better source, maybe there's an adaptor available somewhere? As a last resort maybe I could make an adaptor and then potentially use various other kinds of electrodes, including disposable.
Thanks, Paul
Comments
Paul, hi.
I found this tutorial, just by doing a search.
https://hackaday.io/project/162169-muse-eeg-headset-making-extra-electrode/details
The search was,
https://www.google.com/search?q=muse+micro+usb+electrode+wiring
As you can see there are some other pages with similar info. The electrode wire is soldered to pin 4 on the micro usb connector. The tutorial shows this being done by removing the standard 'touchproof' connector from an EEG electrode. In this case the electrode wire used was one of the FRI spring clip leads.
https://www.fri-fl-shop.com/product-category/leads/fri-leads/
But... these leads primarily mate with the FRI silver chloride comb and cone electrodes. NOT what most EEG electrodes use. But possibly could work for you. See the FRI listings.
An alternative that could work for normal EEG electrodes (cups, disposible, etc.) would be this: just solder a normal stranded wire (say 3 to 4 inches long) to pin 4 of the micro usb. This wire would be stripped say 1/16 inch on the usb side, then soldered and strain relief / capped as shown in the tutorial. An electronic tech could do this for you. The other end of the 3 inch wire, would be stripped to say 1/4 inch and tinned to prevent strands coming loose. Then clamp the wire in one of these clips:
https://www.amazon.com/Wago-221-412-LEVER-NUTS-Conductor-Connectors/dp/B06XH6WW4D/
Now then, with your regular EEG cup electrodes, you would figure out how much wire you need, then cut off the wire at that length from cup. 8 to 12 inches should be enough to reach anywhere on the head. Strip the end to 1/4 inch, and clamp in the other port of the connector.
William
The reason I suggest cutting EEG wire relatively short, is that EEG wires dangling off the head, can cause noise artifacts if the wire is long or moving about. Typical cup electrodes might come with 5 or more feet of wire. Clearly overkill for Muse use.
This guy is charging $50, pretty steep price for what you can solder on your own. Does Muse sell a cable?
https://docs.google.com/document/d/1CGsimrSyLjyH7mXBcm0LEOw83m-nEqd6ImoSHwTtoJM/edit
Another way to go is just get the cable from Muse, and use the spring connector idea I already mentioned.
Thanks William that's extremely helpful. Fifty bucks is the price I pay direct from Myndlift so I suppose it's the going rate ¯_(ツ)_/¯. It would be interesting to try dry connectors. Also, the spring clip idea is good, that way I can use whatever I like.
If you already have Myndlift, just choose where to cut the cable, strip both ends, and connect with the spring clip. So now you can in the future substitute any other cup electrode you buy.
Here is another way to purchase the micro usb cable, PRE WIRED.
https://www.amazon.com/YCS-Basics-Micro-Female-Extension/dp/B0134XUJN2
Most manufactured micro usb cables just have FOUR wires in the cable: +5 power, ground, and plus and minus data wires. This cable has ALL FIVE wires, including pin 4 / wire 4, which is the 'ID' wire used by Muse electrode. According to the comments on this Amazon listing, the ID wire is blue, but you should check with an ohmmeter to be sure. Typical colors for the other wires might be:
So with this cable, you cut off the female micro usb. I'd suggest at 4 or 6 inches from the male, that should be plenty. Open and strip back the sheath outer plastic an inch or two. That will reveal the inner colored wires. After checking with your ohmmeter that pin 4 is indeed the blue wire, you could just clip / remove the other 4 wires. Wrap with tape so the wire ends are not exposed or shorted. Strip 1/4 inch insulation from end of blue wire, and use the spring clip previously mentioned.
Actually, easier than "check with an ohmmeter to be sure", is to just strip the end of the blue wire, and touch it (finger on and off), while the Muse is recording from the external electrode. You should see the time series signal trace jump when the finger is present. And settle back to zero when finger is off.