Polargraph? Polarshield? PolargraphSD? Huh?
A Polargraph is what I decided to call this drawing machine that I made, but it also describes the output. The machine is a simple device, that draws picture using a normal pen, some motors and some string. It is only just good enough to get the job done, and in keeping with this technical brevity, I’m going to spare you more explanations about how it works: The pictures tell the story better.
It’s called a polargraph because when I was making it, I thought of it as using a dual-polar coordinates system internally, rather than the regular cartesian system we (and computer systems) tend to use.
In fact, it doesn’t use a polar system at all, it’s actually a kind of double-triangulation coordinate system. The angle of each cord is controlled by the length of both cords, rather than by specifying angle and distance as in with a true polar coordinate. The name “Polargraph” remains as an evocative term, but it isn’t accurate.
The mechanism is not wholly original: I have mainly taken inspiration from Hektor the spraycan robot, but in researching my machine came across prior art in the form of the AS200 drawbot and Harvey Moon’s drawing machine. And draftsmen will recognise this as a primitive, gravity assisted pen plotter. An awesome one.
The application that drives it from the computer is written in Processing. It decodes a bitmap and creates a map of the file using a polar coordinates system, recording pixel position, size and brightness. The hardware requests each pixel in turn, and renders it on the page using it’s own shading and movement algorithms. You can also use it for plain plotter-type drawings, because it reads drawings in as SVG vector art files. It’s not the most accurate plotter in the world, but it was good enough for Wes Nijssen to draw out a giant papercraft polarbear with.
The whole system is fairly technologically agnostic, I have written an instructable that shows how to put one together based on an Arduino microcontroller and an Adafruit Motorshield, along with a couple of stepper motors.
Well, I’m glad you asked! A PolargraphSD is the drawing machine I use myself, and am selling in batches. It is based on an Arduino MEGA2560 board, with a custom designed and fabricated add-on board (called a Polarshield) that combines a pair of high current, microstepping motor drivers for reduced noise and increased smoothness, and a combination of an SD card reader and touchscreen LCD that means this machine can be used untethered from a computer. The vastly increased memory means that new features, such as the norwegian pixel style, circular pixel and vector sprites are possible, and I’ve still got plans for lots more things to do with it.
The big sell.
You can buy full assembled, tested machines (just add a pen, paper and a surface to draw on), or parts-only “vitamin” kits that contain just the unusual parts. I sell these things at the Polargraph Shop. I’m not making my fortune off you guys, but I do take it seriously. I really enjoy this project, and I think it’s a beautifully simple concept and design, it’s slow, but rewarding.
What’s in a name?
Polargraph is a particular brand of drawing machine. It is often used in a generic way to describe any of these kinds of machine, and I take that as a compliment to the ubiquity of the project, but it shouldn’t really be used except when referring to this Polargraph project.
It is not a generic name for a drawbot, and the term was not in use before this project began. Well, you know, except to refer to polar graphs.