Bouncing a laser off of a spinning mirror creates an amazing effect with smoke and fog, but YouTuber “Normal Universe” made it even better with an Arduino.
This video starts out by introducing the concept of “laser sky,” which seems like a fun idea. There is, however, a chance that the mirrors wouldn’t spin, potentially pointing a laser continuously at a bystander, possibly damaging his or her eyes. To prevent this, the YouTuber added a photoresistor and LED to sense the spinning mirrors, then programmed an Arduino Uno to cut off the laser if it’s stopped for whatever reason.
Normal Universe goes on to explain the electronic concept behind it as well as the Arduino code involved, so even if this effect isn’t your cup of tea, the photoresistor/voltage divider setup could still be quite useful.
You can find a detailed breakdown of the project in the video below!