EDA or ElectroDermal Activity measures skin conductivity with 2 electrodes placed on each finger (of the same hand). Actually we do not quite need electrodes, simple jumper cables (holding wires made of copper and aluminum) suffice to be in contact with our skin. One finger receives tiny current which flows to the other finger as well, and their conductivity rises with perspiration because more electrolytes or salt is secreted.
This technique is based on the paper from MIT: Poh et al. A wearable sensor for unobtrusive, long-term assessment of electrodermal activity. IEEE Transactions on Biomedical Engineering
Their Empatica smartwatch uses Op-Amp for amplifying the signal and can measure EDA directly from the wrist with high precision.
Also, I would like to thank Ullo company and Jeremy Frey for sharing the EDA circuit schematics (made in KiCAD) and Arduino code (original GitHub repo) with us.
List of things you need:
- Arduino UNO (ATMega328P)
- Operational Amplifier (LM358) or any other equivalent e.g. TLC2272
- Four resistors (three of 100K and one of 1M)
- Four capacitors 0.1uF
- A lot of jumper cables
One breadboard (if you do not want to solder anything yet)
Watch video where I link the cables and test the EDA precision