Biosensor Array Galvanic Skin Response - Revision history

Mct: add category

2018-04-11T19:19:57Z

add category

← Older revision		Revision as of 19:19, 11 April 2018
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			[[Category:Biosensor Array]]

	====== This page is part of the [[Biosensor Array]] Project ======		====== This page is part of the [[Biosensor Array]] Project ======

Hef: Robot: Cosmetic changes

2014-03-17T14:17:45Z

Robot: Cosmetic changes

← Older revision		Revision as of 14:17, 17 March 2014
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	== Team Members ==		== Team Members ==

	Primarily researched and prototyped by [[User:pdp7\|Drew Fustini]] after handover from Phil Strong. Please check with Drew for any clarification.		Primarily researched and prototyped by [[User:pdp7\|Drew Fustini]] after handover from Phil Strong. Please check with Drew for any clarification.

	== Current GSR sensor prototype ==		== Current GSR sensor prototype ==
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	http://produceconsumerobot.com/truth/content/GSR_schematic_04.png		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, referred to as the Truth Meter, 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.		This circuit was created by Sean for an earlier version of his Truth Wristband project. This circuit, referred to as the Truth Meter, 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 Truth Meter circuit is featured in Make Magazine Vol 26 (Spring 2011) in the biosensor article written by Sean.		The Truth Meter circuit is featured in Make Magazine Vol 26 (Spring 2011) in the biosensor article written by Sean.
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	== Truth Wristband ==		== Truth Wristband ==

	The GGHC biosensor GSR sensor is based on a earlier version of Sean's work. His latest GSR is the Truth Wristband v5. This circuit has just a low pass filter with the high pass filter done in software on the PIC.		The GGHC biosensor GSR sensor is based on a earlier version of Sean's work. His latest GSR is the Truth Wristband v5. This circuit has just a low pass filter with the high pass filter done in software on the PIC.

	* Truth Wristband kit video		* Truth Wristband kit video
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	== Finger contacts ==		== Finger contacts ==

	One key part of GSR is how the two probes will attach to the body to measure skin resistance. All GSR projects I found use the fingers, either one or two.		One key part of GSR is how the two probes will attach to the body to measure skin resistance. All GSR projects I found use the fingers, either one or two.

	Options:		Options:

	* Thumbtack		* Thumbtack
	** The first circuit I built was the [http://www.arduinoevilgenius.com/projects 'Evil Genius...Arduino'] book Lie Detector circuit which used thumbtacks in a breadboard. I also used this when I built the [http://www.chris3000.com/archive/galvanic-skin-response/ Chris3000 GSR] circuit but didn't get very good results.		** The first circuit I built was the [http://www.arduinoevilgenius.com/projects 'Evil Genius...Arduino'] book Lie Detector circuit which used thumbtacks in a breadboard. I also used this when I built the [http://www.chris3000.com/archive/galvanic-skin-response/ Chris3000 GSR] circuit but didn't get very good results.
	* Nuts		* Nuts
	** [http://courses.cit.cornell.edu/ee476/FinalProjects/s2006/hmm32_pjw32/index.html Cornell EDA] and [http://www.chris3000.com/archive/galvanic-skin-response/ Chris3000 GSR] use nuts soldered onto the ends of wires. I never tried this.		** [http://courses.cit.cornell.edu/ee476/FinalProjects/s2006/hmm32_pjw32/index.html Cornell EDA] and [http://www.chris3000.com/archive/galvanic-skin-response/ Chris3000 GSR] use nuts soldered onto the ends of wires. I never tried this.
	* One Finger Strap		* One Finger Strap
	** I ordered the [http://www.makershed.com/ProductDetails.asp?ProductCode=MKSM1&ampClick=19209 Truth Wristband kit] which came with finger strap which I built. It goes onto one finger and has two silver tabs in it which as the two GSR probes.		** I ordered the [http://www.makershed.com/ProductDetails.asp?ProductCode=MKSM1&ampClick=19209 Truth Wristband kit] which came with finger strap which I built. It goes onto one finger and has two silver tabs in it which as the two GSR probes.
	* Two Finger Straps		* Two Finger Straps
	** I built these according to the [http://makeprojects.com/Project/The-Truth-Meter/703/1 Truth Meter] instructions. Velcro tape has copper foil attached with a wire soldered onto it.		** I built these according to the [http://makeprojects.com/Project/The-Truth-Meter/703/1 Truth Meter] instructions. Velcro tape has copper foil attached with a wire soldered onto it.

	Issues:		Issues:

	* Neither thumbtack or nut is ideal as one needs to press against or hold onto. Ideally for the biosensor array, one needs to be able to move freely within the classroom		* Neither thumbtack or nut is ideal as one needs to press against or hold onto. Ideally for the biosensor array, one needs to be able to move freely within the classroom
	* Both one and two finger straps generate a good signal if hand is held still. However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance. This registers as a false positive GSR event.		* Both one and two finger straps generate a good signal if hand is held still. However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance. This registers as a false positive GSR event.
	* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [[Biosensor Array Galvanic Skin Response Spurious Input \| advice on spurious input]]:		* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [[Biosensor Array Galvanic Skin Response Spurious Input\|advice on spurious input]]:

	<code>		<code>
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	== 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:		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:

	http://courses.cit.cornell.edu/ee476/FinalProjects/s2006/hmm32_pjw32/hardware.png		http://courses.cit.cornell.edu/ee476/FinalProjects/s2006/hmm32_pjw32/hardware.png

	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.		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.		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 by Minn State Univ. This project used a Wheatstone bridge and an instrumentation amp IC. The link on the Cornell EDA page is broken but it is still available via the wayback machine at:		The Cornell EDA project was based on this GSR sensor for MRI machine monitoring by Minn State Univ. This project used a Wheatstone bridge and an instrumentation amp IC. The link on the Cornell EDA page is broken but it is still available via the wayback machine at:

	http://web.archive.org/*/http://physweb.mnstate.edu/shastri/EDABoxPaper.ppt		http://web.archive.org/*/http://physweb.mnstate.edu/shastri/EDABoxPaper.ppt

Pdp7: /* Finger contacts */

2011-05-01T19:51:27Z

Finger contacts

← Older revision	Revision as of 19:51, 1 May 2011
(No difference)

Pdp7: /* Finger contacts */

2011-05-01T19:51:27Z

Finger contacts

@@ Line 60: / Line 60: @@
 * Neither thumbtack or nut is ideal as one needs to press against or hold onto.  Ideally for the biosensor array, one needs to be able to move freely within the classroom
 * Both one and two finger straps generate a good signal if hand is held still.  However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance.  This registers as a false positive GSR event.
-* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [[Biosensor Array Galvanic Skin Response Spurious Input | advice on spurious input]].
+* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [[Biosensor Array Galvanic Skin Response Spurious Input | advice on spurious input]]:
 == Measuring Actual Skin Conductance ==

Pdp7: /* Finger contacts */

2011-05-01T19:50:25Z

Finger contacts

← Older revision	Revision as of 19:50, 1 May 2011
(No difference)

Pdp7: /* Finger contacts */

2011-05-01T19:50:25Z

Finger contacts

← Older revision		Revision as of 19:50, 1 May 2011
Line 60:		Line 60:
	* Neither thumbtack or nut is ideal as one needs to press against or hold onto. Ideally for the biosensor array, one needs to be able to move freely within the classroom		* Neither thumbtack or nut is ideal as one needs to press against or hold onto. Ideally for the biosensor array, one needs to be able to move freely within the classroom
	* Both one and two finger straps generate a good signal if hand is held still. However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance. This registers as a false positive GSR event.		* Both one and two finger straps generate a good signal if hand is held still. However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance. This registers as a false positive GSR event.
	* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [~~Biosensor_Array_Galvanic_Skin_Response_Spurious_Input~~ advice on spurious input].		* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [[Biosensor Array Galvanic Skin Response Spurious Input \| advice on spurious input]].

	== Measuring Actual Skin Conductance ==		== Measuring Actual Skin Conductance ==

Pdp7: /* Finger contacts */

2011-05-01T19:47:35Z

Finger contacts

← Older revision	Revision as of 19:47, 1 May 2011
(No difference)

Pdp7: /* Finger contacts */

2011-05-01T19:47:35Z

Finger contacts

← Older revision		Revision as of 19:47, 1 May 2011
Line 60:		Line 60:
	* Neither thumbtack or nut is ideal as one needs to press against or hold onto. Ideally for the biosensor array, one needs to be able to move freely within the classroom		* Neither thumbtack or nut is ideal as one needs to press against or hold onto. Ideally for the biosensor array, one needs to be able to move freely within the classroom
	* Both one and two finger straps generate a good signal if hand is held still. However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance. This registers as a false positive GSR event.		* Both one and two finger straps generate a good signal if hand is held still. However, movement of the finger like bending causes the contact between the skin and cuff to change which alters the resistance. This registers as a false positive GSR event.
	* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [~~http://http://wiki.pumpingstationone.org/index.php?title=~~Biosensor_Array_Galvanic_Skin_Response_Spurious_Input advice on spurious input].		* I contacted [http://produceconsumerobot.com/truth/ Sean Montgomery] regarding this problem who gave this [Biosensor_Array_Galvanic_Skin_Response_Spurious_Input advice on spurious input].

	== Measuring Actual Skin Conductance ==		== Measuring Actual Skin Conductance ==

Pdp7: /* Finger cuffs & contacts */

2011-05-01T19:46:41Z

Finger cuffs & contacts

← Older revision	Revision as of 19:46, 1 May 2011
(No difference)

Pdp7: /* Finger cuffs & contacts */

2011-05-01T19:46:41Z

Finger cuffs & contacts

← Older revision		Revision as of 19:46, 1 May 2011
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	http://www.produceconsumerobot.com/truth/content/Truth_Circuit.png		http://www.produceconsumerobot.com/truth/content/Truth_Circuit.png

	== Finger ~~cuffs &~~ contacts ==		== Finger contacts ==

	One key part of GSR is how the two probes will attach to the body to measure skin resistance. All GSR projects I found use the fingers, either one or two.		One key part of GSR is how the two probes will attach to the body to measure skin resistance. All GSR projects I found use the fingers, either one or two.