Galvanic Skin Response Sensor:
You can't get more
simple than the Galvanic Skin Response GSR sensor. It is just a cut 9V LEGO
motor wire and some aluminum foil wrapped around your fingers with tape. I was
inspired by talks by Mindfest panelists Karen Wilkinson and Mike Petrich who
talked about using this type of sensor. I've also found out that the Media Lab
at MIT has a program called the Affective Computing Research Project that also
uses this sensor.
It is popularly known as
a lie detector, but is also used in Biofeedback conditioning. The theory is
that; the more relaxed you are the dryer your skin is and so the higher the
skin’s electrical resistance. When you are under stress your hand sweats and
then the resistance goes down. The range is reported to be 5K to 25K Ohms, but
I'm not sure where the measurement was taken. 5K would relate to a RAW reading
of about 340, while 25K should be around 730.
The magazine Electronics
Now had an nice article on building a Biofeedback Monitor in the December 1996
issue. I have modified their plans for finger probes slightly. You use
"Sticky Back Velcro" and Aluminum Foil to make them. An assembly
diagram and photo of the finished product are shown below. I used the
So far I've found the
range RAW RCX values to vary around 800. I'm trying to see how playing
stressful video games effects my skin resistance. More to come...
Warning: You should only
use this sensor with an RCX running on battery power. Operation with the RCX
plugged into a AC source could result in electrocution.
GSR References:
Barbarello,
James J., Build a Biofeedback Monitor, Electronics Now, Dec. 96, p37-43.
Schwartz, Mark S., and
Andrasik, Frank, Biofeedback, A Practitioner’s Guide,
Brown, Barbara B.,
Ph.D., "New Mind, New Body," Harper & Row,
Web References:
MIT Media Affective Computing Project
Buy LEGO Mindstorms
Online:
Some commercially
available Galvanic Skin Response GSR products: