Creating a Normalized Vegetation Index Sensor with two LEDs

For some time now we’ve been refining the classroom version of our logger with the goal of creating a teaching tool that would open up environmental monitoring to the many instructors operating with ‘minimal’ resources. The three-module design has proven capable over many, many real-world deployments, but the builds we use in the field were highly application specific, and in many cases this made the sensor arrangements too complicated for an undergraduate lab exercise. But our simplified approach to creating a Vegetation Index with two LED's is an open-ended starting point with many fine-tuning options for intro science courses in biology, physics, etc:

Although using garden variety LED’s with no spec introduced several non-optimal aspects wrt frequency & bandwidth, the trial successfully distinguished ‘healthy’ vs ‘unhealthy’ plant leaves where a simple visual inspection could not. So there's alot of hand-wavy unknowns in there, and working with transmittance rather than reflectance bends the rules a bit: but keep in mind this was meant from the start to be a conceptual demonstration, rather than a rigorous tool. From a teaching point of view, students would have to create "custom calibrations" for their one-of-a-kind LED combination & for each plant species they work on - but that's actually a useful exercise in and of itself. This fun little hack really has legs in that educational context.


Very nice project, give me some light headache before end of reading, but thx for sharing.


Nice work! Consider posting on Public Lab or one of the other public science sites.

We've had a project thread running on Public Lab for several years. They have an incredible community of tinkerers there!

I realize that the EDU focused stuff coming out of our project may have limited application outside the envro. course labs, but I still post it here because the playground continues to be the most important starting point for people starting new projects. You never know when our weird little experiments will be just the thing someone is looking for.