Mad Cow, That's How

The Concept That Ate My Brain

Plot Ness Monster is likely the world's cheapest (and cheapest) 3 axis computer controlled stepper driven gadget ever built.

This is based on a PIC 16F877. If you don't know what that is, then you'll sleep quite well, compared to Those Who Do.

Note: No plans are offered nor considered, because nobody in their right mind would build something this way. See ebay and the web for simpler, more efficient, more costly approaches. The only thing I like is the controller board, and it needs a second iteration itself.

Note: You should have the same joy I had. Visit this page for how: How To Spend A Couple Hours Sloughing Off Picture Paper To Make A PCB What is really the tragedy is that before making this, I'd look at others' circuits on the web, and note how they couldn't solder a TIP120 transistor straight at all. I vowed I would not suffer that fate. And as you can see, I keep my vows, damn straight. Not! ARGH. They work though, and will be in a box anyhow. So I won't be selling them as sculptures after all, I guess. Pooey.

Note: Much aid and technical assistance was gained via Dr. Electron, AKA Ted Spencer, somewhere up in Canada. Muchos Thankies.

Note: too many notes.

Now hit your Back Button and regain your sanity before I turn this on.

Too late, it was turned on.

Shown in re-creation below (sans dot-plopper attachment) is the semi-dismal result of Plot Ness Monster, which is essentially too cruddy to be used for other than testing the software and motion control. Time for Plot Ness Monster II.

The beast is 2 years old at this point and is being rebuilt soon after being abandoned way back then. Second image shows best sharpie marker dot-plopper result with slipping axis, all displayed for amusement, and to invite condolences.

Specs (Note: this was not built for CNC purposes, but for airbrushing and foam sculpting, be kind)

Max Resolution : .5 to 1mm (half step vs full).
Originally the beastie was set up for threaded rods which yielded a single step generating a move of .0000000000000000000000000001 inch per step, once every galactic rotation. Time was warped, and many died at that speed because chopper drives and servos were not in the picture, so cables were used instead.

Once cables were installed, work was actually done. Until we realized it was basically futile. Use a geared belt, or a 5 pitch threaded rod. Don't worry. Be happier.

The Spec-tacle : 16F877 programmed on a PC (argh), beastie run from a Mac G4 running OS X using a Keyspan USA28Xb serial to USB adapter.

More Specs:

Cost : About $300 or less, or $100 more than that. Motors, $100. Electronics and etching, $50. Programmer and software, $50. Wood, $50. Miscellaneous : $50. Drill Press (recommended) : $90.

3 motors. One Solemn Purpose. 4 limit switches. Limiting that purpose.
X Axis : Parallel rule cable drive. Works a spiffy.
Y Axis : Lamp chain drive. Works a spiffy. (2 to 1 difference over X drive, easy to compensate for in software)
Z Axis : 1/4-20 threaded rod. Works like Time Has Stopped. Then, as if it has taken a break for millenia, then stopped for 5 Big Bang cycles totalling 36 billion years each. Slow is what we mean. Useless for height sculpting currently, only for setting a basic height and there you go.

Motor to pulley axle attach : clear plastic tubing, tube clamp (lame, but works, and provides dampening)

The carriage can go out 1/2 each way for a total working area of about 29 x 39 inches. Which would only take 2 weeks to render at one dot per step, best resolution (.5 mm)

Drive program : PIC basic hack attack using the wonderful OSHON Software's PicSimulator IDE and a SparkFun Electronics programmer or two, onboard programming socket there now

Free advice : don't go cheap on the legs like this, you'll regret it the rest of your plot ness monster days.

The output, using a very very fine pointed sharpie marker at max resolution. The sharpie outlasted the attempt, and my patience. (took about 20 minutes or more for this small piece) The image was dithered using a Floyd-Steinberg algorithm.

Main board with additional components, junction blocks, and programmer cable attach. And lights. And transformer and rectifier. 9v battery runs the chip. Transformer powers the steppers. Solenoids use additional 12V power supply from a 12v backup battery. (too much current draw otherwise). Yes, it does indeed all work. Imagine what would have been possible had it been done -right-. But hey, not bad for like $250-300 total.

Showing interface for 2 solenoids on Z axis control, driven from main chip engine above

Updated, Originated, Nay, Begat On May 6, 2005. Nah, updated on April 13, 2007.