What are Stepper Motors?

In chapter one of Scribes’ Descent, you’ll find this line:

“The hum of vent fans and the whir of stepper motors blended into a sound she’d come to think of as her personal theme song.”

The term stepper motor might seem like a term I made up for the Scribeverse, but it’s a common device in our world. Especially in 3D printers. If you were thinking of Steppenwolf, that refers to a novel, a theater, a coyote, a DC comic character, and a rock band. You don’t want to know how long I spent thinking of how to blend all those things into a meme 😁

Anyhow, this is a stepper motor. Or at least a circuit diagram of one:

Not as exciting as a coyote with an electric guitar in one paw and an Electro-Axe in the other, but it’s way more practical.

Here’s how it works: send current through a coil on the stator (the outer ring shown in the image above) to create an electromagnet. This attracts the rotor (the bar magnet in the middle), which makes the rotor turn by a small angle. Then remove current from that coil and send it to the next coil over, making the rotor turn a bit more. Another step, if you will. As this continues around the stator, the rotor will keep spinning.

If you keep current flowing through just one coil, the rotor will hold that position. We think of motors as constantly spinning, but sometimes we need them to turn by tiny, precise amounts and then hold still there for a while. Stepper motors are great for that.

But so are servomotors (aka servos). For those familiar with electrical engineering, you may wonder why Mallory hears stepper motors instead of servos while running her 3D printer. If servos are similar to stepper motors, but can support higher torque, why not? It’s because servos are much more expensive and require an extra control circuit to handle signal feedback.

Mallory would also have stepper motors in many of her mini drones and in her CNC milling machines. CNC milling helps us fabricate parts that are impossible to make by hand–something a roboticist like Mallory would use every day. But we’ll save that topic for another month 😀

I’ve written a huge world building guide for the Scribeverse that’s crammed with cultural details–many of which haven’t made it into the books. Reply and let me know if you’d like me to showcase some of those in future newsletters.

Writing update: I’ve been posting chapters of Scribes Aflame on https://scribophile.com for critique. If you’d like to set up a free account on that site and critique them, go for it!

See you next month,
Dylan West

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