CD datalogger

thingiverse

Three 3D printed components bridge a servo to a stepper motor, powering a data plotter that's perfect for continuous, around-the-clock tracking of temperature, humidity or any other variable you want to monitor. The adapter on the stepper motor shaft allows you to clamp an old CD or DVD, which will rotate at a steady pace, determined by how long it takes to complete one full rotation. Meanwhile, the servo motor tracks the value of whatever parameter you're measuring and drives the pen holder accordingly. Not into physics? You can still use this setup as a spirograph.