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Biosensor Array Galvanic Skin Response (view source)
Revision as of 19:00, 1 May 2011
, 19:00, 1 May 2011no edit summary
Primary source of prototype is: [http://produceconsumerobot.com/truth/ Truth Wristband]
Primary source of prototype is: [http://produceconsumerobot.com/truth/ 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:
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
Schematic:
http://produceconsumerobot.com/truth/content/GSR_schematic_04.png
http://produceconsumerobot.com/truth/content/GSR_schematic_04.png
== Measuring Actual Skin Conductance ==
== Measuring Actual Skin Conductance ==
Some projects like the [http://courses.cit.cornell.edu/ee476/FinalProjects/s2006/hmm32_pjw32/index.html 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.
Some projects like the [http://courses.cit.cornell.edu/ee476/FinalProjects/s2006/hmm32_pjw32/index.html 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. Drew tried both with LM324 quad opamp using 2x voltage follower (to buffer) and 1x as the difference amplifier but saw no signal on the scope. Drew also tried using dual Micrcochip Op-Amp MCP6002 as voltage follower to buffer each input going into the TI INA114 instrumentation amp.
However, no appropriate GSR signal was seen on scope unlike the above Truth wristband circuits by Sean Montgomery. Further development may likely would have resulted in working Wheatstone bridge-based circuit however, time did not allow given and working circuit of a different type was already acheived.
The Cornell EDA project was based on this GSR sensor for MRI machine monitoring. The link on the Cornell EDA page is broken but it is still
http://web.archive.org/*/http://physweb.mnstate.edu/shastri/EDABoxPaper.ppt
Note the circuit using a wheatstone bridge and amplifier is also referred to as a bridge transducer amplifier like in the TI INA114 datasheet on page 12: http://focus.ti.com/lit/ds/symlink/ina114.pdf
== Related Links ==
== Related Links ==
