Electrodes for GSR BioFeedback Device

Electrodes

Silver is considered one the best electrode materials around. We can capitalize on this by using two U.S. dimes for our electrodes. The cable we’ll use is a shielded 2-conductor. The shielding is a copper braided wire that surrounds two insulated wires in the center of the cable. Remove about 2 inches of the outer cable jacket, and separate the shielding from the insulated wires. Strip ½ inch of insulation off the center wires.

Soldering the wires to the dimes is a little tricky if you haven’t done much soldering, see Figure 3. Place the tip of your soldering iron on the coin, and keep it there till the coin becomes hot enough to melt solder on it. This takes about 1-2 minutes of continuous heating. At this point melt a small puddle of solder on the coin, and place the bare end of one of the insulated wires into the puddle. Remove the soldering iron from the coin. Keep the wire in place until the solder solidifies. Repeat the procedure for the other coin, but solder the shielding along with the wire to this coin. This will be the ground electrode


Figure 3

Figure 3 - The electrode holder

The palm of the hand is very sensitive to galvanic changes, so it is therefore the area of choice. To secure the dime electrodes to the palm of the hand I made a small palm-fitting electrode holder out of ¾ inch pinewood. You only need a couple of square inches practically any piece of scrap can be used, see drawing. After cutting the wood to the proper shape, drill a ¼ inch hole through the center as shown to feed the cable through. Then glue, epoxy or hot glue the electrodes to the wood block as shown. To finish off the hand electrode, attach a rubber band or elastic material to the base so that it covers the electrodes. This material is what will secure the holder to your hand.


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