An assembly diagram and photo of the finished product are shown below. You use “Sticky Back Velcro” and Aluminum Foil to make them. I have modified their plans for finger probes slightly. The magazine Electronics Now had an nice article on building a Biofeedback Monitor in the December 1996 issue. Two of the wires aren’t used, while the others are soldered to the electrode wires as shown in the photo below. Remember these wires are insulated with paint! To make a connection, you need to vaporize the paint off by adding a little solder to the last few millimeters of the wire. The colors might not be standard, so you will need to figure out which wire is which. All you need to do is attach a heaver stranded wire to the little wire that was headed to the left earphone and another to the one that was headed to the microphone. If you cut and strip the wire of a hands-free handset, you will find the 4 wires from the plug as shown below. However, the wires in cables like this have a special enamel paint insulation that you have to vaporize by at least tinning them with hot solder. It isn’t a bad way to go if you aren’t too skilled at soldering. You could probably also do this with a hands-free microphone/headphone for example. The little wires from the 4 elements of the plug are soldered to the terminal strip in order from tip to base. The plug came from an adapter cable I happened to already have and all I did was cut the rest of the cable off and strip the wires.
#GALVANIC SKIN RESPONSE GRAPH HOW TO#
It isn’t very pretty, but it allowed me to easily switch parts and do some initial testing before I figured out how to do everything without the parts you see. I thought I’d show you my first prototype of the interface. The simple connection diagram below seems to work for most smartphones, but Samsung phones need an additional resistor discussed further down. Initially, I thought I’d have to add some electronics to the path, but it turns out that the work can be done in software. Oddly the ground connection is NOT the base but rather the second ring up. They use a single 3.5mm connector that has 4 connections rather than the typical three you see used for stereo headphones for example. The obvious way to generate an AC signal for the microphone circuit to pick up would be the headphone output.Ĭonveniently, both the microphone and headphone connections are in the same place. However, if the frequency is kept low enough, the skin’s resistance to low frequencies should be about the same as DC. This is a problem because the microphone circuitry only inputs alternating current or AC since sound is essentially alternating vibrations.
#GALVANIC SKIN RESPONSE GRAPH SKIN#
Normally skin resistance is measured with direct current or DC. The one available electrical input on a phone is for an external “hands-free” microphone. However, these would require considerable effort and would not likely be something easy to reproduce by amateur scientists. The traditional solution would be to build an external device and communicate with the phone using WIFI, Bluetooth, or maybe even sneak in through the USB port. Some interesting information about GSR can also be found on the iMotions website. Used in lie detectors (polygraph) and biofeedback devices, the measurement is actually quite simple but frequently associated with expensive equipment. Galvanic Skin Response GSR or Electrodermal Activity is the study of the change in human skin conductivity (resistance) under different psychological conditions.