Specific info about "Non 3D-Printed Parts" for Ultra Cortex Mark 4
Hi,
we’re currently in the process of building a device (Cython + Ultra Cortex Mark 4) for some experiments with a few friends. And we decided to build it all ourselves as a learning experience. We figured that should be doable also based on this forum discussion - http://openbci.com/forum/index.php?p=/discussion/921/ultracortex-mark-iv-electrodes-units
There are a few things that we weren't able to really figure out from the documentation (or perhaps I am just bad at searching).
Here's the table with all the parts needed taken from the shop page
Question 1)
We can obtain the screws and ribbon cables, however, I can see some springs in this picture as well?
The springs are not mentioned in the “What parts come in the box” table, so my question is whether the springs used are following the same rationale and specifications as those in M3, mentioned here? https://docs.openbci.com/docs/04AddOns/01-Headwear/MarkIII
Question 2)
Ear clips are sourced directly from the Fri-Fl shop, right? Or is it necessary to get some special connector or wiring with them?
https://www.fri-fl-shop.com/product/td-430-silver-disc-electrode-ear-clip/
Question 3)
I'm fairly certain that the spikey units are these ones. https://www.fri-fl-shop.com/product/new-longer-5mm-spike-disposable-reusable-dry-eeg-electrode-tde-210/
The question is what kind of wiring? Is it the one suggested on the website? https://www.fri-fl-shop.com/product/tde-207xx-1-5-mm-safety-jack-for-eeg-electrodes-specify-color-and-length/
Question 4)
Do you have any special dry electrodes or are those still from Fri-Fl as well? The link to the dry electrodes being used with M3 is now being redirected to TDE-201. https://www.fri-fl-shop.com/product/tde-201/
Question 5)
Comfort units were 3D printed or injection molded I presume. Is this STL from Ultra Cortex M3 still relevant or were there any changes for M4? If so, where could I get the STL for that? Or is a comfort unit only the electrode holder without anything in it?
https://github.com/OpenBCI/Ultracortex/blob/master/Mark_III_Nova/STLs/MECH_PARTS/Comfy_Insert.stl
Thanks for your great work and for your help!
Comments
Bolek, hi.
I'm not sure I understand your question. You are not interested in purchasing the Mark IV "Print It Yourself" kit? My understanding is that the dimensions are too small to 3D print these parts. They were injection molded to make them fit smoothly in this size that is much much smaller than the Mark III electrode holders. Mark III did allow 3D printing of the holders.
The FRI dry electrodes are used in both Mark III and Mark IV.
Regards, William
To clarify, the electrode holder proper (screw, electrode, and plunger), must slide VERY smoothly inside the octobolt that encloses it. 3D printing leaves pronounced ridges that will obstruct this smooth sliding. Additionally the cable is attached to the holder, via what could be called a "crimp wire nut". These are unique hard to find items, I've looked online; could not find them. They are custom made in China. One end has a nut like thread. The other is crimped (with a crimping tool) onto the end of the wire.
In Mark III, the dimensions were large enough that an actual nut could be used, and the wire was hand wrapped onto the bolt. Then nut threaded on and tightened.
Hi William, thanks for the replies.
We were thinking of printing them as well since we wanted to do the whole thing by ourselves as a sort of DIY project. Based on the conversation here - http://openbci.com/forum/index.php?p=/discussion/921/ultracortex-mark-iv-electrodes-units
But if it must be really that precise and the cable is basically proprietary, then we might go with the "Print it yourself" kit in the end.
The springs are likely different also between Mark III and IV, and I don't think those part numbers are documented. The comfort units have stronger springs than the others. I do not believe you would be happy with the jerky and sticky performance of printed electrode units.
I built the Mark IV with Cyton (no dongle) and WiFi Shield from scratch (PCBs and headset).
PCBs manufactured by JLCPCB.
Two types of springs off eBay:
https://www.ebay.ca/itm/0-8mm-Wire-Diameter-304-Stainless-Steel-Compression-Spring-Pressure-Small-Spring/292808345803?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
https://www.ebay.ca/itm/0-5mm-Wire-Diameter-304-Stainless-Steel-Compression-Spring-Pressure-Small-Spring/292819551923?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
I 3D printed the comfort units and had to play around with the scaling to get them to fit. A bit of work, but definitely do-able.
Spikey, flat, and ear electrodes were purchased from FRI.
If I remember correctly, I believe I got the coloured ribbon cables from SparkFun or one of their distributors.
Hope this helps.
@alwayswearshats, thanks. So you had no problems with the 3D printed grooves on the electrode holders, interfering with smooth sliding? I have the Mark III headset, printed at OpenBCI, whose electrode holders are 3D printed. And they are definitely NOT as smooth as the Mark IV injection molded holders from the shop store.
What did you use instead of the wire crimp nuts?
They were definitely not a smooth fit at the start. Playing around with the scaling and working-in the rough edges of the grooves a few times worked fine for my purposes.
By wire crimp nuts, are you asking about the contacts for the spikey/flat electrodes? Mine don't look like the picture above. I just had a screw and two nuts making contact with the stripped wire tightly in-between. Seemed to work fine.
When I have a chance I can post pictures of my hardware.
Hi @alwayswearshats can u please make one video/tutorial/post or document with all necessary details and post it over here so that everyone can make use of it on how to make MARK IV diy ? It will be very very helpfull for all the learners present here as well as upcomming new learners.We all are facing problems.Please guide us.
awaiting for your response.Let's Do It.
Thanks,
Arpit
Part of the benefit of DIY is learning how to DIY. There is enough information on this forum and online to make your way through. It will take time but you can do it.
Unfortunately, putting a tutorial together would take too much bandwidth that I do not currently have. If this is something that you are passionate it about and have the time, why don't you post a blog of your progress for others to follow?
first of all sorry my intention was not that.
since i am also facing problems to make mark IV diy ..but u had gone through this stage and you are successful so as a student i had just asked you to make the things available so that no one again could suffer problems to make that thing .yes to make things available it will take time.But when u have some time please do it...hope u understand what i want to convey .
Please don't take it personally...
Thasnks,
arpit
The files present in the Follwoing link : https://github.com/OpenBCI/Docs/tree/master/assets/MarkIV/STL_Directory/Injection_Molded_Parts
can be proceed for 3d printing ?
please give some insight regarding that
awaitng for response.
Thanks,
arpit
@arpit, hi. I merged your new thread into this existing one, covering electrode holder parts.
William
Is there any information for the size of the screws used by the electrode holders for Mark IV?