We see a lot of data logging projects but jp3141 created one that caught our eye, with a device that captures the slight variations that occur in AC powerline frequency.

In the US, AC power is generally accepted as being 60Hz, but in actuality, it drifts, as can be observed via the University of Tennessee’s FNET service. jp3141’s Teensy 3.2-based device uses two of the board’s FlexTimer Module interrupts (FTMs) to measure the frequency of the power line, plus calibrate the onboard 48MHz clock using an external GPS’s 1pps calibration pulse.

Data is transmitted both via the Teensy’s own USB serial, and to a Raspberry Pi Zero W where it is logged and graphed via a Python script. A 9V AC adapter powers both boards at 5V DC, as well as providing the 60Hz AC sample to be filtered and measured.

An example of drift over time can be seen in the plot below. More information, as well as the Teensy code and Python scripts can be found on GitHub.