Joe Street's images of his active electrodes.
Click on the images to get a larger view.
I decided to try to make a battery powered version of Jarek's active electrode. I thought about the problem and decided a pin grid on a small board which could mount to the second board which had the amp and power supply was the best solution to my needs. I want these electrodes to be a plug in replacement for passive electrodes and give greater ease of use without making any modifications to modeeg. The idea here is to poke the four gold plated pins on the electrode board through an elastic headband to mate with four female receptacles on the amp board. This allows the electrode to be securely mounted to the headband and yet the elecrtrode could easily be removed if I need to clean it or make a modification to the design. Here I used header strips for the pin grid but they don't need to be so long unless you have very thick hair! I am looking for header strips with shorter pins.
The completed electrodes are 16 mm wide and 32 mm long. The one on the left has a trial version of a cover I dreamed up and I left the other open for the picture. There is a little surface mount switch to save the batteries when not in use. I etched these boards myself for prototyping.
In this shot the pins are not through the eleastic so the electrodes can slide along the elastic headband. One can simply place this headband on the head, wiggle the electrodes to get firm contact and be ready for neurofeedback. It looks like the paste is history! The DRL cable still has a passive silver electrode but paste is not needed on this one when using active electrodes. I put the DRL to my wrist. Currently there are problems in running these electrodes in referential mode. I am still working on this but as they are here they work really well in bipolar pairs.