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Wiring for four sensors

After a mammoth soldering session I now have four sensors hooked up to the Bitalino. This will be the final test before attempting to port the whole lot over to the Arduino Feather Wifi. I’m going with Wifi over Bluetooth for reasons of reliability and bandwidth and because the distance between the Arduino and the computer might be quite large.

So now I have to make some decisions as to electrode placement.

EMG - Electromyography

I want to try to determine components of the facial expression which are indicative of emotional response but not observable by the human eye. Three good sites are Orbicularis, Zygomaticus and Corrugator.

EMG Sensor Placement - Orbicularis, Zygomaticus and Corrugator

I have a slight problem in that the electrodes I have available are on the large side. If this causes difficulties I may have to source some smaller ones. I’m a bit nervous about placing electrodes close to the eye so I’ll try the Corrugator first, I think this might yield some nice involuntary activation.

ECG - Electrocardiography

I have tried this before and got good results with this configuration:

ECG Sensor Placement

EDA - Electrodermal Activity

There are three good sites on the hand for this measurement (there are also sites on the feet but that is probably a bit invasive for public exhibition).

EDA Sensor Placement

I choose site #3 on the palm hoping the subject will move this area less than the fingers and avoid false readings.

EEG - Electroencephalography

This subject could take a whole post (probably a whole book) on it’s own. I am at the moment only measuring using one set of electrodes to read from one portion of the brain. For this test I am fortunate to have a subject (me!) who doesn’t mind having his head shaved so there should be fewer problems related to poor conductivity.

The Neurosky Mind-wave which is a single channel EEG has an electrode placed at Fp1, according to the standard 10-20 system, and a ﬁxed sampling frequency of 512Hz so that seems as good a place to start as any.

EEG Sensor Placement

So I’m off to shave my head before setting the sensors up..

4 Sensors Plugged

As we can see each of the sensors is giving a signal (good), but the data looks a bit wonky (bad). In particular waveform for the EEG sensor is not looking like it should, maxing out at the top and bottom and showing a repetitive nature that looks not to be from an organic source. Next time I’ll try to debug the rig and see if I can get some better results.