“This easy project was developed to test the top speed of a stepper motor controlled by an Adafruit Motorshield as part of a class assignment (University of North Carolina at Charlotte’s Junior Design). After throwing it together, we quickly realized that this became an important diagnostic tool for a larger project. The larger project requires the use of stepper motors, controlled by an Adafruit Motorshield v2. Initially, we used this tachometer to test the top speed of the motors (with no load) to compare against manufacturer specifications. However, we found that this served nicely a code-verification tool as well. When a desired motor speed was programmed using a variety of available libraries, we found that the actual motor speeds differed significantly. Since the larger project is a time-based competition, this had significant implications for our end performance. We decided that we could use this to reconcile our programmed speeds with actual speeds rather than spend countless hours trying figure out why we weren’t reaching the speeds we expected. And, in the spirit of good sportsmanship, we wanted to share this with others that might find this as useful as we have. With some slight adjustments to the code, this project can be adapted to many platforms. Generally, the only difference between most platforms and the Teensy is the way the interrupts are attached. I just happened to have a Teensy 3.2 sitting around, collecting dust.”