Use Your Own Electrodes with the foc.us tDCS Headset

The foc.us headset comes with built-on sponge electrodes and has the ability to support wire connected electrodes via a small connector on the back.  You can buy the accessory kit from foc.us and in it receive wire connections for snap-type electrodes (usually stick-on).  For anyone with hair (not me sorry to say), you may want to use sponge electrodes (like the popular Amrex 2×2 or 3×3).  The Amrex electrodes use banana style connectors – so you must adapt the foc.us wires or create your own.  I chose the latter route.

Here’s what you need:

  • Radio-Shack PN 273-334 “Adaptaplug type A” – it measures 2.35mm OD x 0.7mm ID.  If someone has a better connector or source suggestion, please let me know.
  • Wire with the desired connector type at one end. I prefer alligator-clips as they provide great flexibility.
  • Head-shrink tubing (available at Radio Shack)
  • Solder and soldering iron

You can see from the pictures that if you are looking at the back of the connector, pins down, the pin to the right is the Anode (+) when plugged into the headset (I checked this with a DVM). I marked that side of the connector with a red sharpie.

So all that has to be done is solder your leads to the pins, use some heat-shrink tubing to cover them and away you go!

100_1602
(Adaptaplug A from Radio Shack)

100_1604
(
The plug is 2.35mm OD, 0.7mm ID)

100_1605
(
I marked the pin that corresponds to the anode with a red Sharpie)

100_1606
(
A little soldering, some heat-shrink tubing and done!)

With the adapter complete, you have much more flexibility using whatever electrodes you like with the foc.us headset.

BTW wire color does not matter. I just happened to have a bunch of green and yellow clip leads. In this case, I soldered the yellow lead to the anode pin.

You may prefer to buy a cable like this and add lead-wire and connectors that you prefer:

2.35 mm DC Plug for headset
(
Pre-assembled cable from EBay – about $3 with shipping! Search for 2.35mm DC cable.)

One more thought: The connector used for external connections is a bit fragile.  You might want to consider using some Velcro or similar material to provide some strain relief if you frequently use external electrodes.

100_1608
(
A Velcro wrap used for strain relief)

Your ideas and suggestions are welcome!

Brent

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4 comments on “Use Your Own Electrodes with the foc.us tDCS Headset

  1. Where can I obtain new electrode pads / I found some online that are for TENS units are these the same (size vary, are they rated for voltages?) Also they have different connectors would adapters be available to make?

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