EEG Snap Electrodes Information

carlos_lorenzocarlos_lorenzo Spain
in Electrodes

Hi, I'm designing my own EEG active electrodes and some questions regarding the pasive electrodes sold:

  • I'm guessing they're dry electrodes but as its stated nowhere on the product page would like to confirm it.
  • Is there anywhere I could get the exact dimensions of the electrodes as I need to design the hardware around them?
  • I was thinking about connecting them to the pcb via pogo pins as all of the snap cables ive found have the cable horizontally. Is there any other "recommened" way of connecting them with a PCB that will sit right above them?

Thanks :)

Comments

  • danysabdanysab Germany
    edited April 20

    Hi @carlos_lorenzo,
    I’ve build the active electrodes too. I don’t have the measurements but you could easily build your own electrodes from scratch. I’ve used 999 silver wire for the comb electrodes and plate for the Fp1-2. I then coated them with silver chloride using electrolysis (9% NaCl bath or diluted HCl works perfectly). They’re way cheaper to build and work perfectly. The only downside is the AgCl coating can wear off after prolonged use, but if you’re careful enough it’s not gonna happen so easily. Check this guy out it may help https://users.dcc.uchile.cl/~peortega/ae/
    Hope that helps.

  • carlos_lorenzocarlos_lorenzo Spain

    @danysab thanks man. Will definitely look into it

  • danysabdanysab Germany
    edited April 21

    Sure no problem! Here you can have a look on how I did it. I connected the electrodes with the preamp using via wires (typical solution in diy pcb). The single silver wires are soldered on the tiny round fr-4 plate. Of course you can use pin headers or snap header (difficult to get tho) to connect the two. I’m using this method for the new design I’m currently working on (2nd image)

  • carlos_lorenzocarlos_lorenzo Spain

    @danysab
    Hi. That's genuinely helpful. I'm planning on feeding the AE into the standard ads1299. I also have 3 versions of my schematic, one with a DC servo loop to remove offset and one without. Is it necessary? Also have you found that amplification at the electrode level was helpful or was it enough with a voltage follower?
    Thanks in advance

  • danysabdanysab Germany

    I use avdd and avss directly from the board to power the tlc272. My design is based on the schematics from the link I posted and it works pretty well so far. I guess if you use only 8 electrodes it’s fine (usage ~4mA)
    I don’t think the DC servo loop is necessary, since it is (as far as I know) already in the ads1299. Pls check the data sheet because I’m not 100% sure.

    You then need to build an adapter in order to use the AE (Thinkpulse use it too). Here is the one I’ve built. It has pin headers for avdd, avss and gnd (for the cable shielding). The signal cable is then connected in the board.

    Hope I understood your questions.

  • carlos_lorenzocarlos_lorenzo Spain

    @danysab
    Yup thanks :)

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