Surplus Stepper Motors

I've been looking for cheap stepper motors for a couple weeks now.

Published on Thursday, 24 March 2011

I've been looking for cheap stepper motors for a couple weeks now, and I've realized something: modern printers do not have stepper motors, and while scanners do seem to have them, modern scanners tend to have very small stepper motors. Digging through the local Deseret Industries for cheap scanners from which to extract stepper motors the other day, I had an epiphany: typewriters. Typewriters are ideal for a couple reasons:

  • They should be available for practically nothing, since, well, they're practically worthless.
  • They should have at least a couple stepper motors in them, one for the paper tractor and one for the print head.
  • They shouldn't be using the newer DC-motor-plus-encoder drive, because there aren't any newer typewriters.
  • They should have beefier stepper motors, because they're all old and beefy. The fundamental operation of the print head dictates heavier-duty components.

It turns out that most of this is true, but I'll get to that later. First, I'll tackle the point about availability.

There is a serious lack of cheap surplus typewriters out there. My theory is that all the people smart enough to know what they're worth just threw them away, and we're left with people who think they're still valuable, and therefore are looking to get $50-$200 out of them. There was one at the DI for $10, though, and I decided to risk it, even though there were scanners available cheaper that I KNEW would have a stepper inside.

What I discovered inside was a treasure-trove of steppers. There were two identical steppers for the paper tractor and the print head, and an additional bonus stepper (albeit smaller) to drive the daisy wheel. The matched set are bigger than the one I pulled out of the old scanner, and the third is physically larger, but I haven't measured torque on it to know if it's more powerful. They are rated for 22V, and are "50 ohm" and "100 ohm", which means that the resistance of the entire coil is 100 and 200 ohms, respectively, when they're being driven as bipolar motors.