In early 2017 I had a conversation with another caver regarding battery life in cave lights. He refered to a web site that has some rather old data on it. I got to thinking about it and realized I could do better.
I have a Raspberry Pi model B. It has a GPIO bus which can be connected to a huge variety of sensors. Amazon has several light intensity sensors. The one I bought was about $6.00. A link to the vendor's web site is below. There is a newer version of the sensor called TLS2591. Both sensors are also available from Amazon.
The hardest part of this project was finding and installing the Python libraries needed to run the TLS2561. I finally found a usable set of libraries on GitHub in a project called tentacle_pi.
The PowerPoint slide deck goes in to details on how I did the testing. The Excel spreadsheet contains all of the data I collected. You can use this data to create your own graphs. Here is one graph showing data from the StenLight running at medium brightness.
