There are two components in offset voltage cased by electrodes First a DC offset and Second a drift. In addition there two other offsets First a current offset caused by the different input currents to the amplifier and Second a voltage caused by the different voltages
I have been searching for days on the Internet to find DRY, reusable EEG electrodes that are not pronged- we need them to be flat because the spiked ones are too uncomfortable over a long period of time. I can't seem to find any- any suggestions? I am also open to pronged electrodes made out of comfortable and flexible material but the ones produced by Cogniotics are out of our price range. An electrode similar to the ones pictured here would be great, except they do not seem to be selling them (http://itersnews.com/?p=92960).
We have a whole thread of past posts on dry electrodes. I merged your question into that thread. Look through some of the posts here. This thread has mentioned in the past the FRI, Cognionics, IMEC electrodes.
Have you looked at the smooth cone shaped electrodes that FRI makes? These are the ones used on the forehead with the Ultracortex.
Also see this thread for silver chloride buttons that snap into ECG female connectors.
It's likely that this material could be printed into "semi-soft" combs that are splayed somewhat like the Cognionics, and could possibly have a bit of flex. The end tips could also be rounded to minimize the "pointy" effect.
Re: stainless steel, this would likely not be very good, there may be galvanic voltage effects with other metals.
Re: the FRI ear clip. Instead of using that on the scalp, use the cones or the flat buttons.
Using the cone or flat silver chloride electrodes in an area with hair, will require that you carefully brush back the hair around the contact area to expose some scalp area. Then also will need moderate pressure to get skin contact. Also checkout the saline idea.
This company sells dry spring loaded gold pin comb electrodes. That apparently snap into standard ECG/EEG female snap connectors. This means you could likely use them with any cap or strap system which has mounting holes or sockets. Such as the FRI velcro, the g.tec g.GAMMAcap, etc. What doesnt quite add up is why they show impedance as 200K to 500K ohms.
Having found out Openbci does not work with bioexplorer / brain-trainer (I wish there was a way). I am looking for a alternative to the electrocap they use which seem expensive and you have to use the gel.
Any updates on the dry comb type cheap caps?
Should I do a Optima brain Amp with somedry comb like electrodes or the above gold pin comb electrodes in a cap.
Any other ideas. Not so keen on Velcro made ones and brainnet looks cheap and has bad reviews for quality.Does caputron have anything that can be made? Aren't those Gamma ones as expensive as the electrocaps?
Do the Florida research instruments electrodes fit in the size 10 or size 4 dritz? Do you need both snaps or could you just solder a wire to the size 10 dritz and use it as a female connector to the FRi electrodes?
No, they are larger because there is a hole to inject gel if you do not get a good connection. OpenBCI has a way to connect to them See their instructions for their headset.
Yes, what you are suggesting would work, the FRI does snap into the large #10 Dritz, according to past posts. The #4 was only used to snap into female ECG connectors. If you solder directly to the #10, be sure to use some type of strain relief or hot glue / epoxy so as not to pull directly on the soldered wire attachment.
These look to have some substantial advantages to the previous combs:
* the tips are much more smooth and rounded, less "spikey", so will likely feel more comfortable, especially in a headset or bands that are pressing the electrode into the skin under spring or band tension.
* the longer comb pins will work better for those with longer / deeper hair.
You can see photo of original (more spikey) comb here,
Comments
We have a whole thread of past posts on dry electrodes. I merged your question into that thread. Look through some of the posts here. This thread has mentioned in the past the FRI, Cognionics, IMEC electrodes.
Have you looked at the smooth cone shaped electrodes that FRI makes? These are the ones used on the forehead with the Ultracortex.
Also see this thread for silver chloride buttons that snap into ECG female connectors.
http://openbci.com/forum/index.php?p=/discussion/244/saline-based-electrodes-no-paste-needed
If you are not using a dry comb, then it may be possible to get a scalp connection with enough pressure and a flat or cone shape.
One last item to mention is the new highly conductive 3D printing filament,
http://openbci.com/forum/index.php?p=/discussion/comment/3821/#Comment_3821
It's likely that this material could be printed into "semi-soft" combs that are splayed somewhat like the Cognionics, and could possibly have a bit of flex. The end tips could also be rounded to minimize the "pointy" effect.
Re: stainless steel, this would likely not be very good, there may be galvanic voltage effects with other metals.
Re: the FRI ear clip. Instead of using that on the scalp, use the cones or the flat buttons.
William
Celeste