Wireless GSR Progress
by Carson Reynolds
In order to develop a wireless galvanic skin response (GSR) sensor several design issues need to be overcome. Firstly, is the design of a GSR amplifier that doesn’t require tuning and is precise. Secondly, this amplifier needs to be interfaced with a wireless transmitter. Lastly, the entire device needs to be packaged in a manner that makes it comfortable to use. Recent work with the Mindgames Group at Media Lab Europe, has produced several designs that satisfy these requirements.
Galvanic skin response is a term that covers a variety of electrical phenomena on the surface of the skin. The psychophysiology community recommends measuring skin conductivity response (SCR), because it is a variety of electrodermal activity that maps accurately to the activity of sweat glands [1,2]. This means that a sensor should treat the skin as a conductor and keep voltage constant across the surface of the skin.
In recent months we have developed 15 designs for GSR amplifiers. After informal testing, we’ve settled on a single design, which measures SCR. From the schematic for this design, we see that it consists of signal conditioning circuitry and a PIC microcontroller. The microcontroller interfaces with wireless transmitters via a UART port. A printed circuit board prototype for this sensor has been constructed and inital tests performed.
The skin conductivity response consists of two components: the tonic and phasic [3]. The tonic is slow moving, oscillating over the course of days. The phasic is fast moving, and spikes sharply when a person is startled, and generally increases when a person is psychologically aroused. Many GSR and SCR amplifiers include some adjustment so that the tonic portion can be removed and the phasic measured more accurately. The design presented above, includes a potentiometer to trim the tonic portion off and adjust the amplifer’s output.
A new design removes the need for this adjustment by incorporating a 16-bit analog to digital converter (ADC) with enough resolution to ignore the tonic offset. The electrical schematic for this approach is considerably less complex, due mainly to the removal of the PIC microcontroller. The ADC chosen provides a I2C interface which can be interfaced with wireless transmitters like the BlueCore 2. The resulting board is considerably smaller. So much smaller that it could conceivably be packaged into a design the size of a ring.
What remains is to fabricate an interface board which physically connects to the BlueCore 2 Bluetooth chipset. A physical housing for this also needs to be constructed. One design being considered is an ambient display [4] in the shape of an orb that would house the electronics. A second, more ambitious design, would be a ring sensor that would consist of 3 layers: amplifier board, bluetooth board, and watch-style battery.
One interesting application for this sensor could be a tug-of-war version of Relax To Win, in which a crowd of participants play the game and simultaneously form a Bluetooth network that forwards sensed information.
[1] Lykken, D. T., & Venables, P. (1971). Direct measurement of skin conductance: A proposal for standardization. Psychophysiology, 8. 656-672.
[2] Fowles, D. C., Christie, M.J., Edelberg, R., Grings, W.W., Lykken, D.T., Venables, P.H. (1981): Committee report: Publication recommendations for electrodermal measurements. Psychophysiology Research. 18. 232-9.
[3] Boucsein, W. (1992). Electrodermal Activity, Plenum Series in Behavioral Psychophysiology and Medicine, Plenum Press.
[4] Wisneski, C., Ishii, H., Bahley, A., Gorbet, M., Braver, S., Ullmer, B., Yarin, P. (1998). Ambient Displays: Turning Architectural Space into an Interface between People and Digital Information: Cooperative Buildings. Springer Verlag, February 25-26, 1998. http://citeseer.nj.nec.com/wisneski98ambient.html
Dear Sir, I highly appreciate your work on this as I am also interested to do experiments on pets, Since I am not a electronics students I am at loss with the circuit schematic, Will you kindly send me a complete circuit schematic showing details ofcomponents used, computer connection and the software/program used to evaluate the results received, Please,
Thanks and appreciations,
king
Hello,
I am greatrly appreciate your works posted on the web. I am currently seeking for the project like this (WIRELESS GSR). I would appreciate if you could give me permission to design your unique product. Please send hardware and firmware of the Wireless GSR that interfaces to PIC.
Thank you for your consideration.
Mike
trvaph2@aol.com
Hi
I really like the research you have posted here. It is very interesting. You probably must have receive thousands of requests to build your wireless gsr. I hope you can make another exception for an enthusiast like me. I would really like to build the wireless gsr device with your permission. I really appreciate it if you could send me the necessary info(schematic, components, instructions, firmware, etc.) to build the device.
Thank you
Sorry, my e-mail is
yeonghong@hotmail.com
Hi.
I would really like to build the wireless gsr device with others owners modifications. I really appreciate it if you could send me the necessary info(schematic, components, instructions, firmware, etc.) to build my device.
..the electric schematic!..i forget tell it!. thanx.
I am a second year student of Naturopathy and I am just researching EFT, GSR meters etc. I would like to build one but need all the details, my son will help me. Is it possible to get your instruction sheets please? I would be grateful
Barb
Neat stuff! I was wondering if the pcb layout, parts listing would be available? Thanks!!
tom
Great,
Now we can generate “The Mama’s mood detection” device in our garage. Is it possible to get some instructions (components, instructions, firmware) to build one?
Thanks a lot,
David Barnes
Hello im a student and I would like to build it, please send me the necessary info(schematic, components, instructions, firmware, software).
msn: yo_tu50@hotmail.com
If you do send out information needed to build this project (parts list, at least…) then do send them to me as well. Thanks.
I would like to build this for our students to do some experiments in affective computing. Can I request for infos on how to build this one? Thanks.
If you do send information related to the wireless gsr project please add me to the list.Thank you!
I am also interested in more information on this project, if you have a chance. Thank you so much!
hello sirs,
can u please provide the circuit diagram for your proposed wireless gsr amplifier
Looks great man. I was wondering what the ZRC component in the schematic is? Never seen one of those.
The ZRC is a Zetex voltage reference p/n ZRC250F03TC. Additionally, there are some new design revisions posted here:
http://bentham.k2.t.u-tokyo.ac.jp/notebook/index.php?s=handwave
https://sonetspace.com/colarruncle mardolui elaine a30b5ac58e