Electrodermal Activity with the Grove GSR

Electrodermal activity (EDA) is basically about the resistive properties of skin. Emotions are often attributed to changes in the resistance of skin, as well as sweat, and are often found in lie detectors. More recently, interesting work has been done on producing products that reliable detect seizures with EDA.

Upon reading up on interesting applications of EDA, I wanted to make my own, but that would require time, which I had little of during the weeks leading to exam block. Obviously I wanted to make a nice pretty little board with two electrodes across the bottom, but each PCB revision would take ages to receive here in Australia. Sure I could probably just prototype it on protoboard, but still I’d need components which I simply don’t have. Then I found the inexpensive Grove GSR … It came in the mail around a week later and I’ve finally got to use it today.

It “kind of” worked, but:

  1. I couldn’t see changes due to breathing
  2. There seemed to be some ridiculous rise time for the sensor and an even more ridiculous fall time, probably attributed to some cap on the board. As a result, I had to turn the sensor on/off every time I polled it (I haven’t tuned it but currently I’ve got a 20 ms off time and 5ms on time; 40Hz sample)

figure Sensor output of Grove GSR. The graph above is generated using pyqtgraph.

In the fact the only thing I could detect was me clenching my wrist. When I clenched my wrist there would be a rise in the EDA reading (i.e. lowering of resistance) which I would assume to be due to the stretching of skin.

Oh, and here’s an interesting EDA project featured on Hackaday