Polygraph Machine

I have decided to create a polygraph machine with my Arduino. From the research I have done on Wikipedia and other internet sources, a polygraph typically has 3 to four "sensors", namely:

  1. Heart Rate
  2. Skin resistance (sweat sensor)
  3. Rate of Respiration
  4. Blood Pressure

For the heart rate sensor, I am trying to create something very similar to the one seen at tinkerish. In fact, it's nearly the exact same, but I do not really care about oxygen levels, so I likely won't worry about the infrared LED for now.

Skin resistance will also be easy (I hope). For this I am going to use two pieces of copper, one attached to the +5 volts pin and the other attached to the analog input pin. If I am understanding things correctly, this will allow me to measure the voltage which is running through my skin. When there is more sweat, resistance will go down and the voltage will go up.

Respiration is slightly tougher. I think that what I am going to do is have a force sensor in a think which wraps around your chest. As you breathe in, the force sensor gets bent, therefore increasing the "force" being applied to the sensor.

Blood pressure, I have no ideas about. So I've pretty much called blood pressure out of the question. I'll be sure to post more pictures and/or videos as I move along.