Using the watch as a skin conductance sensor

Hi!

Well, I guess the easy option is to try and find some existing Bluetooth LE skin conductance sensor, and then interface to that via Bluetooth.

However, if you're willing to do some hacking around then I think it wouldn't be too hard to make something yourself with Bangle.js. Luckily on the heart rate sensor board inside there's already an analog input - some notes about where are here: https://www.espruino.com/Bangle.js+Techn­ical#heart-rate-monitor-pcb

So I'd suggest something like:

• Take the back off the Bangle.js (https://www.espruino.com/Bangle.js+Disas­sembly) and remove the little heart rate window from the back
  
• Unsolder all components from the heart rate monitor PCB
  
• Attach a 200kOhm resistor between the HRM analog input and GND
  
• Attach one wire to the HRM analog input, and one wire to the HRM power pins, and then bring them out through the hole in the back and attach them to two elecrodes.
  
  

You should then be able to get an idea of conductance between the two pads with something like:

Bangle.ioWr(0x80,1); // HRM power on
var value = analogRead(D29); // read HRM value
Bangle.ioWr(0x80,0); // HRM power off