At 15$ per sensor, it's starting to be *really* interesting. Anybody to team-up for collective purchase order?
I received my dritz for the Ag/AgCl electrodes (seems to fit!), but I'm ready to spend few more bucks for more reliable electrodes and... less soldering
I wonder how many "sessions" each sensor is good for, before the chloride portion of the Ag-AgCl starts to wear off. There is a silver plate below that, but the chloride is what give the best signal quality. With silver plate alone you would still get a signal, but then it's technically NOT a Ag-AgCl electrode.
With the flat Ag-AgCl buttons I use in the velcro saline headset -- buttons last about 40 sessions before the coating wears off in patches. Then the buttons must be replaced; only 50 cents per button.
These spring loaded combs put a lot more friction and pressure on the tiny area of the tips. So I would expect they would get less than even half of that, 20 sessions per replacement? Can someone ask Cognionics?
There are ways to re-chloride your silver plated electrodes, perhaps that is another avenue,
Below is the reply I got back from Cognionics. I guess they have really heavy duty plating on their tips; or these buttons I'm using have light plating. :-) Would certainly be worth a "road test" however before pegging the number of sessions as "infinite"... As I mentioned above the chloride layer could disappear and still have conductivity through the silver plate. But that would be a silver electrode and not Ag-AgCl.
Some of the Cognionics headsets also use Active Electrode circuits at each comb sensor. In that case silver or gold or Ag-AgCl would all perform about the same. With passive sensors, electrode metal is more an issue.
Hi William. We have not seen tip wear to be a problem as long as the device is only used on heads.
You can use an alligator clip as an inexpensive alternative. The leads we sell are not the standard snap but allow you to inject gel into the top of the electrode. The top of the electrode has a hole in it so it is also larger than the snap electrode. We sell a package of 25 electrodes and 3 leads for 34.95 and 25 electrodes and 5 leads for $48.95. They are on our web site www.FRI-FL.com
Jake, also read the previous page on this thread. Shows the velcro system from FRI, which would make it easier to hold the sensors in place. And some posts from @ecube showing his snap adapter. In other words, you can make your own leads that attach directly to the snap.
To Karl's great credit, he found a way to bring the price down on these, enormously from what Biopac was selling them for. See that first page. And if you look around on various EEG supply sites, $8 for a touchproof EEG electrode is about as low as they are priced. Of course you can do without the touchproof if you want.
ECG snap connector 5 lead touchproof sets are available for around $30.
Just ran across a recent Kickstarter project using spring loaded active gold contacts. Unsure how comfortable these are, they look large and pointy. They get the spring loaded contacts/pins from this company. Using the INA116 instrumentation amp. (Our ADS1299 delta-sigma design makes IA's unnecessary.) So overall an admirable project, but looks somewhat unwieldy.
I want to buy the package below. I can not find on web site www.fri-fl.com and I don't know to pay. Please help me
"If some OpenBCI people want to try out EEG Dry Electrodes I can offer a special price for Package of 25 Disposable / Reusable Dry Electrodes & 3 Lead Wires (FRI-2140-1) $29.95 and this including shipping. It is a savings of about $10. They can be seen on our web site www.fri-fl.com If anyone is interested send via PayPal $29.95 to [email protected] with a note that it is for the OpenBCI Dry Electrode Offer."
Two weeks for U.S. to Vietnam (not express) package, seems not unreasonable. I believe the $30 price quoted was probably for U.S. orders, and not including extra postage for foreign. If you did not send them extra postage, it might have gone via surface(!)
The time for Europe via USPS First Class is usually about 1 week. Some South American countries can take a month. This is our first order to Veitnam. The main delay is usually in the customs of the person’s country. We are looking into DHL for shipping. I will post the information on our site.
Add it to your shopping cart, and when you check out, enter the code
bcistart
into the coupon box and click "apply coupon". It's directly below the cart's item list. The total will refresh with the discounted price. Then you can finish checking out with paypal.
Kind of a tangential question, but is there anyway to order an extra set of the touchproof to female header pin connectors that comes with the OpenBCI kit?
I'm planning on getting the headband + dry/wet electrode kit from FRI mentioned above,but will need adapters to connect to my board. I see that Chip has a tutorial on eeghacker but I'm hoping to avoid piecing it together if possible.
I'm guessing Joel @biomurph will comment about the touchproof adapter cables. Since these come with all OpenBCI kits, I'm surprised you do not have one. They likely have extra stock of these 8 cable sets.
I also thought of one other way you could make your own header pin adaptors, if you are willing to cut your touchproofs off (say 6 inches from the end). Admittedly a 'kludge', :-) However, these M/F jumpers,
If cut in half, would allow you to splice the female on the electrode cable. And the male onto the touchproof stub. That way you could use your FRI cables either with .1" header connections or with touchproof equipment if that happens sometime down the road in your future.
Thanks for the reply @wjcroft. I actually don't have an OpenBCI kit so that's why I was looking for the touchproof adapters separately...I hope to order a kit at some point though.
I'm interested in doing some EEG recordings + computations, and at the moment I've just been playing around with a couple microcontrollers that I have. I'll be making a board with the ADS1299 as the front-end anyways so a simple option could be to just have the male touchproof jacks right on the PCB itself. Thanks for the tips!
The male touch-proof jacks are a bit expensive and they're pretty large...especially if you're putting 10 on there (8 EEG chan + 1 for the reference + 1 for the bias). So, before you jump in with your own board, do be aware of the increase in size that'll be necessary.
Plastics1 keeps changing their website, but the current webpage for these components is:
I looks like P/N 41828 are the male PCB-mount 1.5 mm touchproof jacks. They're $20.10 for a package of 10, which is cheaper than I remember. Cool. They're still pretty big, though.
As far as I know there is not another connector that is as safe when working with human subjects than the 1.5 mm touch proof plug, Even the .1 female connector that OpenBCI uses could be connected to a pin that has voltage on it.
> Has anyone tried any dry-electrodes sensors which can be used like a wearable headset?
(1) Conor has these same dry combs mounted in his prototypes of the printable headset; spring loaded.
(2) The velcro band/strap concept becomes like a 'headset' if you have several cross straps installed. The whole unit could be lifted off and replaced on your head later without having to reposition each strap. Assuming you are using it on the same person each time.
(3) The g.tec g.GAMMAcap (elastic cap with holes at 10-20 locations) -- would work pretty well as a dry sensor 'headset' with the advantage that the Medium cap fits most people. ("one size fits [almost] all"). (4) The BraiNet elastic hole guide (mentioned earlier on this thread), is another elastic 'cap' like solution.
The Cognionics looks fun, but I'll bet is considerably more expensive.
I asked Cognionics about the Quick-dry 20 headset a few months ago. A fully-populated unit with 19 channels plus reference and ground costs $14,600. A 3-channel unit costs $2800.
Thanks William and Kartik for your comments on products.
Cognionics is way expensive.
I am now thinking about purchasing, g.tec G.GammaCap with G.Sahara electrodes. I want to connect these electrodes to openBCI module.
Can you help me what exactly i have to buy to make this work and estimated cost range.
I looked at the product description, there is no price quote present. Moreover, the G.Sahara electrodes does not come with a connector which can be connected to touchproof connector.
The g.SAHARAbox converts the active electrodes into conventional 'passive' touchproof electrode signals. I never got the price broken out to see what the g.SAHARAbox itself cost.
I'd suggest (as before) just using the reasonable cost g.GAMMAcap with the FRI dry passive electrodes. With the OpenBCI clipped to the rear of the cap or say back of shirt, leads will be quite short. In general, active electrodes drive the price way up (at least with research type equipment).
Comments
$40 each, or $15/sensor in quantities greater than 100:
http://cognionics.com/index.php/products/sensors/flex
Cognionics sensors were successfully used with OpenBCI in a recent exploratorium exhibit:
http://openbci.com/forum/index.php?p=/discussion/319/cognitive-technologies-maker-expo-at-sf-exploratorium
Q 6-19: $30.00
Q 20-39: $25.00
Q 40-99: $20.00
With the flat Ag-AgCl buttons I use in the velcro saline headset -- buttons last about 40 sessions before the coating wears off in patches. Then the buttons must be replaced; only 50 cents per button.
These spring loaded combs put a lot more friction and pressure on the tiny area of the tips. So I would expect they would get less than even half of that, 20 sessions per replacement? Can someone ask Cognionics?
There are ways to re-chloride your silver plated electrodes, perhaps that is another avenue,
https://www.google.com/search?q=making+silver+chloride+electrodes
William
I've gotten prompt responses from Cognionics when using their online contact form:
http://cognionics.com/index.php/contact
You might try asking your questions there and see what they say.
Some of the Cognionics headsets also use Active Electrode circuits at each comb sensor. In that case silver or gold or Ag-AgCl would all perform about the same. With passive sensors, electrode metal is more an issue.
Cognionics, Inc.
[email protected]
(619) 302-8686
You can use an alligator clip as an inexpensive
alternative. The leads we sell are not the standard snap
but allow you to inject gel into the top of the electrode. The top of the electrode has a hole in it so
it is also larger than the snap electrode. We sell a package of 25 electrodes
and 3 leads for 34.95 and 25 electrodes
and 5 leads for $48.95. They are on our
web site www.FRI-FL.com
Karl Zurn
Disposable / Reusable Dry EEG Electrode [TDE-200], TDE-207XX Lead (http://fri-fl-shop.com/product/tde-200/) that are similar? Please help me.
Dear KZurn,
"If some OpenBCI people want to try out EEG Dry Electrodes I
can offer a special price for Package of
25 Disposable / Reusable Dry Electrodes & 3 Lead Wires (FRI-2140-1) $29.95
and this including shipping. It is a
savings of about $10. They can be seen
on our web site www.fri-fl.com If anyone is interested send via PayPal $29.95
to [email protected]
with a note that it is for the OpenBCI Dry Electrode Offer."
[email protected]
Ask them how it was sent and the tracking number. FRI handles the order directly. Other contact info here,
http://www.floridaresearchinstruments.com/contact/
Two weeks for U.S. to Vietnam (not express) package, seems not unreasonable. I believe the $30 price quoted was probably for U.S. orders, and not including extra postage for foreign. If you did not send them extra postage, it might have gone via surface(!)
The time for Europe via USPS First Class is usually
about 1 week. Some South American
countries can take a month. This is our
first order to Veitnam. The main delay
is usually in the customs of the person’s country. We are looking into DHL for
shipping. I will post the information on
our site.
Karl Zurn, Florida Research Instruments Inc., www.fri-fl.com, [email protected]
Here is an easier way to obtain the $15 discount on the headband
set
The webshop link for the headband set is at
http://fri-fl-shop.com/
Add it to your shopping cart, and when you check out, enter the
code
bcistart
into the coupon box and click "apply coupon". It's
directly below the cart's item list. The total will refresh with the discounted
price. Then you can finish checking out with paypal.
Karl Zurn, www.fri-fl.com
I'm guessing Joel @biomurph will comment about the touchproof adapter cables. Since these come with all OpenBCI kits, I'm surprised you do not have one. They likely have extra stock of these 8 cable sets.
I also thought of one other way you could make your own header pin adaptors, if you are willing to cut your touchproofs off (say 6 inches from the end). Admittedly a 'kludge', :-) However, these M/F jumpers,
https://www.adafruit.com/products/826
If cut in half, would allow you to splice the female on the electrode cable. And the male onto the touchproof stub. That way you could use your FRI cables either with .1" header connections or with touchproof equipment if that happens sometime down the road in your future.
is as safe when working with human subjects than the 1.5 mm touch proof plug, Even the .1 female connector that OpenBCI
uses could be connected to a pin that has voltage on it.
(4) The BraiNet elastic hole guide (mentioned earlier on this thread), is another elastic 'cap' like solution.
http://openbci.com/forum/index.php?p=/search&Search=saharabox
The g.SAHARAbox converts the active electrodes into conventional 'passive' touchproof electrode signals. I never got the price broken out to see what the g.SAHARAbox itself cost.
I'd suggest (as before) just using the reasonable cost g.GAMMAcap with the FRI dry passive electrodes. With the OpenBCI clipped to the rear of the cap or say back of shirt, leads will be quite short. In general, active electrodes drive the price way up (at least with research type equipment).