Archive for the ‘Galvanic Skin Response’ Category

Galvanic Skin Response Sensor with Arduino on your iPhone

Friday, September 30th, 2011

Anna Dumitriu, Tom Keene and Alex May have led a 2-day workshop at the 17th International Symposium on Electronic Art (ISEA 2011) about Biosensing and Networked Performance and instructed participants how to build and calibrate their own iPhone compatible/connectable Galvanic Skin Response Sensors (GSR) to record subtle changes in their emotional arousal.


A GSR sensor connects to an Arduino board. The Arduino generates an audio tone mapped to value of electrical resistance in the skin. A filter removes a 32KHz sampling frequency contained within the output signal, which is recieved by an iPhone/Android mobile phone via their microphone input.

According to the makers, when a 9v battery is attached, the device takes 1 second to startup, then plays a 3 second startup sequence (composed by Caryl Mann). Two sensors placed on the skin will then measure subtle changes in skin resistance. The sweat glands are controlled by the sympathetic nervous system, so skin conductance can be used as an indication of psychological or physiological arousal.

Parts list and build instructions available here. Arduino code here.

Very interesting work demonstrating the direct communication with the iPhone. We also like the signal filtering (or smoothing) implementation on the Arduino code!

Bio Sensors Board by Arduino

Wednesday, July 27th, 2011

Recently I was looking over the net for projects like ECG and GSR boards for the Aduino and came accross this link:

http://www.arduino.cc/en/Main/BioSensorsBoard

It is listed under the main Hardware that usually presents all the oficial Arduino boards.

According to the link, the is able to read the heart rate and galvanic skin response of two people at the same time just by placing their hands on the sensor pads.

 

Having a look at the board, one can tell, (apart from the fact that it is a complete PCB board) that it contains all the essential Arduino I/O pins, but has no place for the ATmega chip or other stuff like usb-to-serial driver chip. Most likely it will be a BioSensor shield than a complete Arduino board.

The only visible connector socket is the one on the left corner and most likely it will be the connector for the sensor pads.

I don’t really know for how long this page has been existing or when the board will be officially anounced, but it is definitely great news!! It is more than obvious that Arduino can be used as a great platform to experimen with biosignals and it was just a matter of time for people from the Arduino team to develop a board like this!

Measure your Galvanic skin response

Tuesday, July 26th, 2011

The galvanic skin response (GSR) can be used for capturing the autonomic nerve response as a parameter of the sweat gland function. Due to relatively simplicity of measurement, and a quite good repeatability GSR can be considered to be useful and simple method for examining autonomic nervous system function, specifically the peripheral sympathetic system.

A sample GSR signal of 60 seconds (Source: wikipedia).

The simple psycho-galvanometer was one of the earliest tools of psychological research. A psycho-galvanometer measures the resistance of the skin to the passage of a very small electric current. It has been known for decades that the magnitude of this electrical resistance is affected, not only by the subject’s general mood, but also by immediate emotional reactions. Although these facts have been known for over a hundred years and the first paper to be presented on the subject of the psycho-galvanometer was written by Tarchinoff in 1890, it has only been within the last 25 years that the underlying causes of this change in skin resistance have been discovered.

I have found two guys that have developed their own GSR circuits that utilize Arduino for measuring their skin conductance.

Chris from Chris300 has designed a very simple schematic and also provises both Arduino and Processing codes here.

It uses 3 Op Amps.  One electrode gets 1.5v (from an external battery) and the other electrode has a 1M resistor and a 1M pot going into ground.

Mustafa Bagdatli and Che-Wei Wang share the same circuit and code principles and also provide nice pictures and screenshots about their work.