January 2005, Issue 174

Microcontroller-Based Nitrox Analyer

Like many Circuit Cellar readers, I often find myself combining my enthusiasm for embedded systems with my other interests to come up with engaging design projects. The project I’ll describe in this article is no exception. The Nitrox analyzer in Photo 1 is the result of my interest in a specialized form of diving in which you breath a gas called Nitrox instead of regular air.

Typical recreational dives involve breathing air, which is made up of approximately 21% oxygen (O2) and 79% nitrogen (N2). When you breathe enriched air Nitrox, however, you’re breathing a gas containing more oxygen and less nitrogen than regular air. It’s important for reasons of safety that when breathing Nitrox you know exactly what percentage of oxygen you’re breathing.

I originally considered purchasing an analyzer, but after some thought, I figured that designing one would be a far more rewarding experience. Although I’m always excited to develop and use my own embedded devices, I don’t have a death wish. It’s for this reason that I only use my analyzer as a redundant check of a dive technician’s analyzer. This is also the reason that I must recommend that you use my analyzer only as an example of an interesting embedded device.

For the non-divers out there, a little background information is in order. Scuba diving has several inherent risks that can lead to injury or death. Proper training is necessary to mitigate these risks and to allow you to execute safe dives. Although a comprehensive overview of diving procedures and physiology is beyond the scope of this article, there are a few general principles that are relevant to understanding the functions that my Nitrox analyzer performs.