Hi all - I wanted to experiment with building an EDA sensor following recent (2022) recommendations to use an AC signal rather than DC voltage to run through the fingertips.
There are lots of examples online of EDA sensors (also known as GSR, skin conductance) using DC voltage, but moving to an AC signal requires totally different circuitry.
I have collected various scientific articles telling me how to accomplish this, and I believe I have all the correct tech components at home (MCP6004 op amps), but I'm not getting the right values on my scope.
In the service of open-source creation I'm happy to make a tutorial and publish a clean circuit about this later so that something exists for the makers (I am a uni prof in a music department and my mission is to develop open source cheap methods for real-time biofeedback for artists) but this circuitry problem has me kind of going in circles.
https://www.circuitlab.com/editor/#?id=y2edts43bkbb
This is what I am trying to make work, the AC signal is a 100hz sine at 1.0 gain coming from the line out of a Teensy Audio shield.
The "varR" are the two EDA probes on either side, simulating 1M skin resistance..but really I'm just picking up two wires and pressing them to my fingertips...the signal reacts to my connection but the signal doesn't seem to change with EDA, so it's not a great sensor.
The biasing part works, it's the TIA and possibly the way this whole thing is connected together that isn't working.
Thanks for your patience, I appreciate that this is more of a circuitry problem than a Teensy problem!
There are lots of examples online of EDA sensors (also known as GSR, skin conductance) using DC voltage, but moving to an AC signal requires totally different circuitry.
I have collected various scientific articles telling me how to accomplish this, and I believe I have all the correct tech components at home (MCP6004 op amps), but I'm not getting the right values on my scope.
In the service of open-source creation I'm happy to make a tutorial and publish a clean circuit about this later so that something exists for the makers (I am a uni prof in a music department and my mission is to develop open source cheap methods for real-time biofeedback for artists) but this circuitry problem has me kind of going in circles.
https://www.circuitlab.com/editor/#?id=y2edts43bkbb
This is what I am trying to make work, the AC signal is a 100hz sine at 1.0 gain coming from the line out of a Teensy Audio shield.
The "varR" are the two EDA probes on either side, simulating 1M skin resistance..but really I'm just picking up two wires and pressing them to my fingertips...the signal reacts to my connection but the signal doesn't seem to change with EDA, so it's not a great sensor.
The biasing part works, it's the TIA and possibly the way this whole thing is connected together that isn't working.
Thanks for your patience, I appreciate that this is more of a circuitry problem than a Teensy problem!