Using the Ultracortex Mark IV with a Brainmaster Discovery 24 amp
I am hoping for input. I love the open bci concept!!!
I am using a discovery 24 amp from brainmaster and want to get a headset with 16 channels. As far as I understand, I will be limited to 16 sites and want to do 19 site whole head training in slorretta. Is there a way to get the Mark IV to record/train at 19 sites?
Comments
Garlorco, hi.
The Ultracortex has all the 10-20 sites (sockets) for 19 channel, but normally is only configured for 8 or 16 channels. If you email to contact at openbci.com, I believe you could order 3 additional electrode holder units.
https://shop.openbci.com/collections/frontpage/products/ultracortex-mark-iv
You will need some technician help with the connection to the Discovery. Continue reading. The Ultracortex (UC) is expecting to plug into the header pins on the Cyton mainboard. Cyton has male pins, UC has female connectors (called 'Berg' or 'Dupont') that terminate in the rear of the UC, that mate with these male Cyton pins.
The shop does offer a "touchproof adapter",
https://shop.openbci.com/collections/frontpage/products/touch-proof-electrode-cable-adapter
But this has the wrong sex connectors on BOTH ends of each wire. Sorry to say. (Female Berg and female touchproof.) Your Discovery expects male touchproof.
What I would suggest is to pickup a pack of cheap 'disposable' EEG electrodes. This pack from MVAP has 25 of them, for $18.
https://www.mvapmed.com/electrodes-leads/eeg-cup-electrodes/disposable-cup-electrodes/technomed-disposable-adult-eeg-cup-electrodes.html
Available in 1, 1.5 or 2 meter lengths. Cut off the cable near the electrode end. Then strip the end of each wire (19 for your sites, and a couple more for reference and ground.)
Then from a number of websites, you can purchase a pack of 'jumper cables', such as:
https://www.adafruit.com/product/826
Cut 20 some of these half-way, and strip those wire ends. Now splice each of your male touchproof cables, to a male Berg connector wire. Wrap the splice with good quality electrical tape. Or even better, shrink-wrap and seal with a blow dryer or butane flame.
https://www.amazon.com/560PCS-Heat-Shrink-Tubing-Eventronic/dp/B072PCQ2LW/
Now you can plug the UC into your Discovery. Suggest that you label each touchproof with the 10-20 site name. Also would be wise to 'strain-relief' the incoming cables at the UC, so that they do not drag on, pull on, disconnect from the tension between the headset and the touchproofs.
Regards, William
PS I do realize the Discovery has a DB-25 ribbon connector. But wiring up an adapter for that would be even more technical. Though possible. Electro-cap does publish the pin-out.
I would advise caution with using the Discovery. It's designed for use with Electro-cap and gel. Although this is considered a 'passive' electrode connection, it still gives low impedance and best possible QEEG results.
Using the silver chloride dry electrodes with UC, this is also considered passive electrodes. However your impedance will be higher, and numbers greater than 5K ohms are likely. Also the microvolts amplitude will be somewhat lower, because no electrolyte (gel) is being used.
Brainmaster sells a dry electrode system, but I'm pretty sure it uses 'active' electrodes, which are pre-amplified just behind each comb. Thus there are no impedance issues or drop in amplitude.
William
Thank you so much for your response. Want to make this work. Will consider your words,
https://openbci.com/forum/index.php?p=/discussion/2517/expected-impedance-range-with-ultracortex-cyton-resolved
https://openbci.com/forum/index.php?p=/discussion/comment/13328/#Comment_13328
Thank you so much for this information! You made my week! :-)
I am definitely going to contact OpenBCI to see if they have 3 header pins that can be soldered to the Cyton + Daisy boards! I am doing LORETA scoring at the moment with my OpenBCI with a wet electrode cap (using gel), and those 3 extra channels would be super helpful, as it maximizes the potential of the device :-)
I have a lot of side projects going on with OpenBCI at the moment, and I find it to be a ton of fun. I am a programmer so I am playing around with a lot of MATLAB and Python packages for neurofeedback. I am an expert at controls, and I can definitely create closed-loop entrainment programs for attention, memory, relaxation, etc. I have created closed-loop artificial pancreas systems in MATLAB for fun, so I can definitely do amazing stuff there for the community.
I am also trying to design a case with touchproof electrodes. The best cases are these (ranked)
1. Cyton + Daisy Touchproof Electrode Case: https://www.thingiverse.com/thing:2085981
2. Cyton Touchproof Electrode Case (aesthetically pleasing): https://www.thingiverse.com/thing:3449895
However, I am aiming for something like this (but a less long and a little bit wider): https://raw.githubusercontent.com/OpenElectronicsLab/eeg-mouse-notes/master/images/OpenHardwareExG-rev1-in-case.800.jpg
Ultimately, I want all of the jumper wires on each of the header pins, whether they are used or not. I will have a touchproof adapter for each of the header pins, whether they are ever used or not. So, I will need 39 touchproof adapters, technically, but for aesthetic reasons, I will use 40. Obviously I will only use around 20 of them, especially since I consistently use it for monitoring sleep, which requires some surface EMG recordings for the face. (I have severe restless legs syndrome and I am using this as a defacto sleep lab, along with other devices such as an EMG recorder for the legs, respiration monitor, ECG, and SPO2 monitor).
Hi Squirrel, unfortunately the ADS1299 analog to digital converter chips used by Cyton, only have 8 channels each. The Discovery amp has 24 total channels.
William
William, I sent you an email. I would like to revisit using the Mark IV with my brainmaster amp. Let me know if you got it. Below is the message I put in the email.
Gary, hi.
I see from previous comments on this thread that I gave a detailed, possibly over enthusiastic reply comment in May 2021. That has most of the details on adapting the connectors and adding three additional electrode holders. However, the bad news is that I do not believe the Ultracortex skin impedance, using the passive dry silver chloride combs and cups, is going to work sufficiently with your Discovery. View this thread comment which gives typical impedance ranges we see:
https://openbci.com/forum/index.php?p=/discussion/comment/13328/#Comment_13328
I did post that in the above comments circa May 2021. Perhaps you missed reading that. To summarize, the first paragraph there states:
Now if you read through the rest of that comment text, you can see that the ADS1299 amplifier chip used in the Cyton and Daisy, has an amplifier INPUT impedance of 1 GIGAOHM. Because the input impedance is so high, the passive dry electrodes used in the Ultracortex can work acceptably in most cases. That same comment also links to the EGI Impedance paper, which gives the rational for how the input impedance can allow higher skin impedances.
I checked the spec for Discovery, see page 12 of this doc:
https://brainmaster.com/wp-content/uploads/2020/08/531-362_DiscoveryHardwareUserManual_v1.1_8-24_12.pdf
That states input impedance of greater than 1000 Gigaohms, or 1 TeraOhms. Hmm, I don't know, but I wonder if that figure is accurate? Texas Instruments ADS1299 chip used in Cyton, has one of the highest specs of all the available amplifiers. But Brainmaster is 1000 times better?? Possible.
In any event, your recent comment is stating that less than 15,000 ohms would be required. That is just not what we are seeing with the Ultracortex dry passive system. So I would greatly caution you as far as what you might expect if you assemble this. As you might know, all the other tens of thousands of dollars headsets that Brainmaster offers, are DRY ACTIVE electrode systems, which have a tiny pre-amp behind each electrode. So they are much more forgiving in terms of local skin impedance at each electrode. The passive dry system in Cyton cannot match the performance of such high end headsets.
I'll reply to your email also, if you have followup comments.
William