What do you use to keep your EEG electrodes where they belong? Some devices have the electrode placement built in, like the Muse and Emotiv, but it’s trickier when you’re using something like the OpenEEG or OpenBCI.
I’m using the OpenBCI, and so far I’ve just placed the electrodes with 10–20 paste at approximate 10–20 locations, without any kind of headband/set to hold them in place. It’s not entirely satisfactory. The Ultracortex is quite promising, but expensive. Professional electrode caps are even more expensive, and they use wet electrodes which makes it slower to set up. The closest thing I’ve found is Florida Research Instruments’ EEG headbands, which are reasonably affordable but look somewhat cumbersome.
What do you recommend for headware? Is there something that you know of that fills this niche, or should I build my own?
I plan on using the OpenBCI Ganglion when it comes out and I’m currently printing the UltraCortex MK 3 to work alongside it. Much cheaper to do it yourself, but not a simple task either. Keen to use dry electrodes as well…
Cool! Did you get the $299 print-it-yourself kit? What’s the print time for the Ultracortex? I don’t own a 3D printer, but I have access to a large, finicky dual extruder RepRap derivative — I’m wondering how many times I’d have to fix it to print a complete Ultracortex
The good thing about the Ultracortex is that as a) 3D printing tech improves and goes mainstream, b) the OpenBCI company + user community grows, and c) the design is iterated on, the Ultracortex will become more affordable and probably become a great go-to solution for DIYers.
For now, I think I’ll get a handful of Florida Research Instruments’ dirt-cheap dry electrodes and then experiment with ways to get them in position. If there was some existing item that could be re-purposed into a DIY EEG headset that would be awesome — maybe I could start from an adjustable hardhat or fire helmet, and mod it so the head-support straps cover popular 10–20 locations…
Many neurofeedback practitioners use some variant of saline solution electrodes, because there is no cleanup involved. See the commercial section tab at the site.
FRI got the idea for their velcro system from here. The dry combs take a moderate amount of pressure applied to work well. The Ultracortex provides this with spring pressure. With the strap system you have to tighten the bands sufficiently.
Hardly any pressure is needed with saline electrodes, since the conductive saline solution bridges the gap.
Hey William,
Thanks for the input. I hadn’t seriously considered using saline electrodes with the OpenBCI after my experience with the Emotiv EPOC saline sensors, but your velcro + saline electrode setup is the closest DIY solution I’ve seen. A couple of questions about your experience with dry vs saline electrodes:
How do you find the saline sensors work with hair compared to gold cup + gel or FRI’s dry combs? (Hypothetically, you might be able to make a comb-like saline sensor, out of hardish foam, to get lower electrode impedance on hairy people.)
Does the pressure needed for a good signal make dry combs uncomfortable for long sessions, or is it just a constraint to consider when designing the tightening mechanism for the straps?
If I were to buy a premade saline-electrode headset, which of the options mentioned on your page would you recommend?
As long as you part the hair out of the way so the saline pad gets near the skin, you’re fine. The saline won’t bridge over matted hair that is too thick.
I never tried the FRI straps with their combs. But have heard from others that a fair amount of pressure is needed. For example using a chin strap. Which can just be another piece of velcro. With the Ultracortex that is not needed because of the springs.
Regarding the premade saline systems. I’ve only experienced the EGI sensor net. This is WAY out of reach, costing like $50K with the amp. The net and post systems look reasonable and affordable. Though the DIY velcro straps allow some degree of placement memory between sessions.
Perhaps experiment with a DIY dry comb setup from FRI. You can make your own straps with a hole puncher and the Velcro One-Wrap. You only need a few sensor locations, so just get a small package to trial. The spring ear clips are highly recommended. Otherwise you’d need to mess with tape or paste.
Thanks! I think I’ll try FRI dry-combs to start, and I’ll know that if I don’t find a good way of modding an existent item into an adjustable electrode holder, I can use Velcro One-Wrap. And if it takes too much pressure to get good impedance with the dry combs, I can make chamois-cloth pockets for my existing gold-cup electrodes and add some saline solution, so I won’t get hung out to “dry” if the FRI combs don’t work out
Be sure to order some “cones” as well as the combs. The cone or cup shaped dry sensors are for bare skin areas such as forehead. Or sections without hair. Be sure to get the two spring ear clips as well, combs would feel awful on the earlobes. The ear clips have flat buttons similar to those I use in the saline setup.
Hmm, unfortunately they only include the ear clip with the biggest package. On my site I list the clips from STENS that I use, that you can buy separately. FRI calls the combs ‘dry’ and the cups ‘wet’, but the cups / cones are what you use on bare skin.
Generally you don’t want to mix metal types with your electrodes. Since the FRI stuff is Ag-AgCl, you should use that throughout.
Hey, @curiositry I was wondering what did you do eventually.
I also purchased dry/wet electrodes from FRI but I’ll have to wait patiently at least 20 days until it arrives.
At the moment they’re installed in the adjustable suspension taken out of a hard-hat. It’s like a poor man’s Ultracortex, I suppose. It still needs some fine tuning, but it shows promise.
Yeah, I purchased the exact same package you are describing with the 48 inch leads. Looking forward to it!
Thank you, nice to be here and meet you all.
Nice! I hear rumour from Alexandre Barachant that the Ganglion may perform better with (some types of) dry electrode than the original board. So I am also looking forward to trying out the Ganglion with the FRI electrodes (when my board arrives).
