Measure Steam Engine RPM with Arduino-Powered Stroboscope

Steam engines were integral to the industrial revolution, and steam power— in a different form—provide electrical power to a vast number of people. You may have some vague idea that a steam engine pistons push a wheel in a reciprocating motion, but how does this power source actually work?

As it just so happens, Joop Brokking has obtained one so small that it’s powered by a small beeswax candle, and shows us how it works in the video below. The boiler is first filled with water, then the candle is lit. After a few minutes, the water gets hot enough to bubble up and push the piston over and over after starting the flywheel. The trick here is that as the piston moves, it intermittently aligns with a port that pushes steam in, then a second port that allows it to exhaust at the top. When combined with a flywheel, the system clicks along nicely at around 1850 RPM… But how does Brokking know its speed?

The answer comes at around 5:15 in the video, where he measures it with an Arduino, LED, and potentiometer. He simply adjusts the light to flash at the correct speed with the input potentiometer, eventually making it appear nearly still via a stroboscopic effect. This is then read out of the serial port, giving a convenient way to measure any sort of reciprocating motion.

For another pointless-but-awesome device, check out the solenoid boxer engine model that we covered earlier!