Generators are expensive pieces of equipment. You can get a small low-quality model for a few hundred dollars, but high-quality generators cost thousands or even tens of thousands of dollars. Old cars, on the other hand, can be very cheap — especially if they aren’t roadworthy anymore. Jake von Slatt has a video series explaining how you can convert a junk vehicle with a working engine into a powerful generator.

Most of the cost of a generator is from the engine, and alternator or dynamo with inverter. In this case, the engine is in a Toyota Sienna minivan. The vehicle isn’t worth keeping on the road, but the engine still runs well. And that engine has plenty of power for a generator. The alternator came from a Harbor Freight generator that had a bad engine. To keep the AC voltage output at the steady 60Hz needed for household appliances and tools, von Slatt utilized an Arduino.

The Sienna has a cruise control system that actuates the throttle in an attempt to keep wheel speed consistent. But in this case, von Slatt needed it to keep the engine stable at 3600rpm to maintain 60Hz. So he built a simple circuit around an Arduino Nano Every board and an H-bridge. The Arduino controls the cruise control actuator’s servo motor through the H-bridge while monitoring the alternator output voltage (stepped down to 5V) frequency. If the frequency is too low, the Arduino rotates the cruise control actuator to increase engine speed until the frequency is exactly 60Hz. If the frequency is too low, it does the opposite.

This is a simple and effective way to keep both a discarded car and an old generator out of the scrap yard while providing off-grid power.