Biosensor Array Galvanic Skin Response

Team Members

Primarily researched and prototyped by Drew Fustini after handover from Phil Strong. Please check with Drew for any clarification.

Prototype

Primary source of prototype is: Truth Wristband

Sean Montgomery, owner of the above site, has a GSR circuit that uses no micrcontroller and a low & high pass filter in the circuit to create a 0.48Hz to 4.8Hz band pass:

Schematic http://produceconsumerobot.com/truth/content/GSR_schematic_04.png

This circuit was created by Sean for an earlier version of his Truth Wristband project. This circuit is used at as the biosensor array GSR prototype as it produces a simple analog output that is already filtered. This reduces the complexity of the Arduino code and the graphing display application on the computer.

The circuit is featured in Make Magazine Vol 26 (Spring 2011) in the biosensor article written by Sean.

Make Magazine is now selling a kit on Maker Shed for this circuit:

http://blog.makezine.com/archive/2011/04/new-in-the-maker-shed-galvanic-skin-response-kit.html

A video of the assembly and operation is on that page as well.

Truth Wristband

The prototype is based on a earlier version of Sean's work. His latest is the Truth wristband. This circuit has just a low pass filter with the high pass filter done in software on the PIC.

• Truth Wristband kit video
  • http://www.youtube.com/watch?v=_br59dghZgI

• Truth Wristband kit Maker Shed:
  • http://www.makershed.com/ProductDetails.asp?ProductCode=MKSM1&ampClick=19209

Measuring Actual Skin Conductance

Some projects like the Cornell EDA project used a Wheatstone bridge and op-amp (configured as difference amp). With this circuit and microcontroller software, they were able to calculate the exact resistance of the skin and thus the skin conductance. This would have been a good measurement for the biosensor array but Drew was not able to get their circuit to work correctly.

Related Links

• Arduino GSR project with Processing (with Op Amps): http://www.chris3000.com/archive/galvanic-skin-response/
• Arduino GSR project with Processing UI (no ICs): http://cwwang.com/2008/04/13/gsr-reader/
• Cornell project, EDA Sensor: http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2006/hmm32_pjw32/index.html
• Massimo of Arduino: Heart Rate & GSR shield built on protoshield: http://www.flickr.com/photos/mbanzi/172472639/
• LED output: http://www.youtube.com/watch?v=lPWaGYKQ5ew
• Attached via fingers and wristband: http://www.mustafab.com/blog/?p=437