Joop Brokking has been experimenting with a miniature candle-powered steam engine. It’s an amazing little device, able to push a piston over and over to turn a flywheel, releasing the steam via a mechanically-controlled valve. But just how fast does it go?

Of course, there are a plethora of ways to determine its speed, but Brokking chose to do so using an Arduino Uno, a potentiometer and an LED that’s arranged over the piston assembly. 

The light source is programmed to pulse on and off, with a frequency that can be adjusted using the potentiometer. He then aligned this pulsing with the piston’s cyclic rate, visually “freezing” the device in time. This frequency and RPM numbers are output over the serial monitor, giving him a speed of around 1850 RPM.