Proper way of connecting audio stereo cable to electrode

Other Hardware General Electronics
1

Hello,

I am trying to recreate this project. However I would like to test it using simple coin based electrodes. So my Arduino is connected to board with MAX3003 chip. This board has 3.5mm mini jack to plug in electrodes. I dont want to buy special clips like these right now. I'd like to use my headphones cable.

So my question is how to properly connect 3.5mm audio cable to coins so it would work. I saw people connecting single wire to coin to use it as electrode, but they didn't have mini jack on their boards. Audio stereo cable has 4 wires: left audio, right audio and 2 gound.
I don't know what to do with these ground wires. Should i leave them and connect only audio wires to coin? Or should I also connect these ground wires. Or maybe 1 coin with gound and second without, as one electrode is supposed to be grounded.

From my understanding I should connect ground wires to close the curcuit. However doesn't connecting both audio and ground wire to single coin result in no signal form electrode at all?

I would appreciate any help with understanding this topic.

2

Audio stereo cable has 4 wires: left audio, right audio and 2 gound.

There should be 3 connections* called "tip", "ring" and "sleeve". It's called a 3.5mm TRS connector.

The left & right can have separate shields but they are connected together at the connector as one ground. You can trim-off one of those "ground" connections or you can connect them together. (That may not be ground in your set-up, just at the other connections are not left & right.)

The Sparkfun cable uses different terminology, "REF", END", "MID".

Your color codes are probably different so you should "ohm out" the connections to check them.

  • Smart phones and newer laptops use a 4-conductor TRRS connector with an additional connection for a microphone.