Velcro saline sensor headset
Here is a link and a couple photos of the velcro based saline sensor system. Saline sensor systems have the advantage that they do not need paste or gel, hence application and cleanup is easier. The Emotiv EPOC is an example of a saline system that uses small saline soaked felt pads.
The article includes instructions on how you can build this yourself. Either with the gold cup sensors you received with OpenBCI, or with Silver / Silver Chloride sensor buttons. Also included is a list of manufacturers I am aware of, who make commercial saline systems that can be purchased.
View of the headset in 5 channel Open Focus alpha synchrony configuration (Fpz Cz Oz T3 T4). Reference is using linked ears, Bias is at ~ Fz.
View with the headset in place. Cable bundle tacked at shirt collar. OpenBCI clipped to shirt (visible in article photo). LiPo battery in my pants pocket.
William
PS I have a couple other pages I'm composing on Brainbay neurofeedback designs. Will post those shortly.
Comments
The page link above is intended to show that saline sensor electrodes can be constructed in a wide variety of ways. The basic principle is an EEG electrode (of any type), with a layer of saline soaked absorbent material (chamois, felt or thin sponge), between the skin and the electrode.
The electrode material made of silver chloride is only a necessity if working with frequencies less than .1 hz. The page also has a 'commercial' headset page where it shows other metallic cup sensors employed in saline systems.
William
Is that the Velstretch you are using?
https://www.google.com/search?q=velstretch
I'll post a photo of this material. It actually is compatible with the Velcro One-Wrap. It is a stretchy 1 inch wide strap, that has a surface that hook material can mate with. So it mates with the hook side of the One-Wrap. On the very end of the Velstretch is about a 5 inch length of hook only material. This appears to be exactly the same as the hook side of the One-Wrap.
The downside of the Velstretch is it is loopy on BOTH sides. When using the One-Wrap in the saline system, you place the soft loopy side next to the skin. And leave the hooks facing outward. So for example if you used the Velstretch as the circumferential "hat-band", it would only mate with One-Wrap straps that have the hook side facing INWARD. Sigh. Well, I think this form of stretchy strap that is compatible with One-Wrap still will have some uses. One way might be to just portions of it interspersed, rather than one continuous hat band of Velstretch.
My guess is that with all the 3D printer guys out there, we'll see some interesting hybrids of printed electrode holders and the types of velcro.
Post a photo or other info on your CPAP inspired headset.
Cheers,
William
I really like William's post. Good idea, and easy to set up. The only question I have is, if you're using the Velcro setup to place the electrodes in the correct positions, how do you define and mark the site positions on the 10/20 system? Maybe I missed this somewhere along the line, but I'm not clear about this.
Stan
If you've used cup electrodes and paste for a little while, you get very familiar with the standard 10-20 site locations and how to 'eyeball' their placement. Cup electrodes are used by the majority of neurofeedback practitioners, so this is straightforward to learn.
http://openbci.com/forum/index.php?p=/discussion/176/placing-electrode-sensors-on-the-scalp
The landmarks are the "hat band" around the circumference of the head (which contains the Fp1 Fp2 T3 T4 O1 O2 sites). And the 'top' of the head, typically above the ears, halfway between the nasion and inion (Cz). The Frontal Fz line is halfway between Cz and Fpz. The Parietal Pz is halfway between Cz and Oz. Similar for locating X3, X4; halfway down.
This same saline sensor idea can be used with other headgear such as the BraiNet or g.tec g.GAMMAcap. See the thread on caps,
http://openbci.com/forum/index.php?p=/discussion/191/elastic-head-caps-electro-cap-g-gammacap-etc
William
I have considered the BrainNet system in the past. I know they are approved as single use. Do you know how robust they are. I would like to replace them frequently with multiple uses
Thanks
George
George
Does that make sense?
William
What sensors and saline are you using? Once the Ag-AgCl button sensor with saline soaked chamois contacts the skin, very little downward pressure is needed. The current is flowing through the saline/skin interface which is not very pressure dependent. Be sure that you have parted the hair at the site so that the chamois can contact the scalp more easily. The saline can go through a small amount of hair, but not layers of it.
One other adaptation you can use, is to incorporate an elastic velcro for the hatband. Velcro does make this material and the Velcro One-Wrap straps can stick to it. The elastic then allows more force to be applied. Athletic sweat bands can also be used. I use the elastic setup for tDCS when I'm applying Amrex sponge holders. These cover larger 2x2 inch areas so do need more downward pressure.