Wandering aimlessly through that great and tangled web we call the Web, I discovered the Den of Iniquity , where we are invited to perform the following:

  1. Grab the nearest book.
  2. Open the book to page 123.
  3. Find the fifth sentence.
  4. Post the text of the sentence in your journal along with these instructions.
  5. Don’t search around and look for the "coolest" book you can find. Do what’s actually next to you

"You can readily identify mating phases when there is a small resistance though the wire pair." From Robot Builder’s Bonanza , first edition, by Gordon McComb. It was under some papers, a Linux Journal , and the AS&S catalog.

In this section of the book, the author discusses stepper motors. Unlike a typical DC motor, the coils of a stepper motor must be energized in a specific sequence for the motor to turn. Although this means that the controlling circuity must be more complex, the stepper motor’s motion can be more precisely controlled, and can supply more torque at lower speeds. Thus they are ideal for devices that must move to precise positions, such as in floppy disk drives . Hmm, do people still those? I guess not.

An ideal application of stepper motors is in robotics. For example, in something I’ve wanted to build for quite a while, a CNC machine . This is basically a robot that operates a power tool, typically a drill or router, but sometimes an etching laser, a water jet cutter, a pen, icing dispenser, or whatever the situation calls for. In fact, a fabricator is basically the same sort of machine, but with a tool that deposits material (or hardens plastic ), rather than cutting material away.

The reason the CNC machine had bubbled to the top of the stack is because I was recently seized by a desire to build a telescope. It would certainly be nice to make the robot do all the fiddly cutting and drilling, which, if I were to do by hand, would almost certainly introduce enough slop to render the entire device useleless. Of course, stepper motors would have their uses here as well, in the positioning of the scope and the accounting for the motion of the Earth.

And when all was said and done, I could then torment visitors with photos like the following, and the tales of all the stepper motors that made it possible.


Originally uploaded by astroferg .

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