Monthly Archives: October 2012

Hack-O-Lantern

Halloween fast approaches, and I still haven’t managed to make that electroluminsencent Riddler costume I’ve been dreaming about for the last two years. But this year I did manage to come up with a nifty Hack-O-Lantern that uses an Arduino and a pair of diffusers that I printed on my MakerBot Replicator. Here’s what the animation looks like, including my new favorite function, derp().

My apologies for the soul-deadening ambient light in the video. The Hack-O-Lantern looks a lot cooler in person, although if I had more time I’d try to boost the voltage to the LED’s and brighten them up a bit. Right now they’re running off straight off the Arduino, and I didn’t want to burn out any pins by driving too much juice. Maybe next year.

You don’t need to use an Arduino to use these diffusers: if you’d rather just stick a couple of LED’s in there with a watch battery taped to the leads, that will work just fine. The LED’s in the top photo are running in series off 4X 1.2V NIMH 2500 mAh rechargable C cells, and they look great.

The diffuser has a slight lip on the back that you can use to score your pumpkin’s flesh before cutting.

Nightmare fuel, anyone? Here’s all 14 LEDs soldered to hookup wire, fed through the pumpkin’s eye holes.

Once I connected the LEDs to pins 0-13 on an old Arduino Duemilanove I had kicking around (SCORE for finding a set of headers I’d forgotten I ordered six months ago), I put the whole contraption in a plastic bag so the pumpkin guts couldn’t short the hardware.

Working inside that cavity gives you a lot more respect for brain surgeons.

If you’ve carved a pumpkin recently, you’ve probably got some seeds kicking around. Here’s what I’ve been doing with them lately:

Zheng3 Szechuan Pumpkin Seeds

approximately 1.5 cups of pumpkin seeds, washed.
1 tablespoon doubianjiang
1 teaspoon light soy sauce
1 teaspoon hot chili oil
2 tablespoons peanut oil
1 tablespoon Szechuan peppercorns

Mix everything except the peppercorns in a bowl and toss to coat. Set aside for an hour to marinate.

Toast the peppercorns in a wok over medium heat until fragrant. Crush with a mortar and pestle.

Spread the pumpkin seeds and marinade evenly on a flat baking tray. Bake at 350° for about 20 minutes. Sprinkle with the crushed peppercorns and serve.

If you can’t find doubianjiang and you’re not willing to wait for a shipment from Amazon you can probably substitute some garlic powder mixed with Sriacha rooster sauce.

Approximating the flavor and mouthfeel of Szechuan peppercorns is more difficult. Try this:

Dip a jalapeño pepper in powdered laundry detergent and suck on it for 30 seconds. Then put your lips across the terminals of a 9V battery.

It tastes better than it sounds, believe me.

You can download the STL’s and Arduino code here.

His nibs.

I started using a Wacom Intuos 2 tablet in 1999 after struggling with a mouse-induced repetitive stress injury. I’ve been holding the same stylus pretty much every day, for hours a day, for the last twelve years.

Over time, the nibs eventually wear out, and I’m left wondering where I left that tiny bag of replacement nibs I bought from Wacom three years ago to replace the tiny bag of replacement nibs I lost six years ago.

Now I have a Replicator, and I can print my own highly precise pieces of plastic. I’m a big believer in Taking It Just A Little Too Far, so I’ve designed a nib based on the slicing end of a Shaolin spade.

The Shaolin spade (月牙铲, or yuèyáchǎn for my fellow xuésheng) was the favored weapon of drunken monk Lu Zhishen, made famous to those without an interest in classical Chinese literature by Max Brooks’ Zombie Survival Guide and the fine Kurt Russell vehicle Big Trouble in Little China.


The nib should work for any Wacom stylus. Here it’s pictured in my Bamboo, which I use for work when I’m traveling.

My original plan was to include the Shaolin spade in the Zheng3 Cocktail Arsenal, but the tip is too wide to be thrusting through maraschino cherries. It should make a dandy calligraphic nib for those so inclined.

If you’re the kind of person who cares enough about the quality of a digital brush stroke to 3D print custom nibs for a Wacom tablet, you deserve a step-by-step tutorial on how to do it.

This is a really precise, but very simple print. The nib’s shaft needs to be sized so that it fits the bore of the Wacom pen and can be removed with the tiniest effort, but not so loose that it falls out when one begins to draw with the stylus.

I did a lot of trial and error to get the nib diameter correct, because my four-dollar hardware store calipers produced a measurement that was way, way too thick to fit into the pen. A radius of .065 cm seems to do it when printing with the following method. I’m assuming there’s some contraction/expansion/plastic real-world-weirdness that doesn’t show up when the design isn’t all vertices and electrons.

Note that I’m printing with PLA.

ReplicatorG Settings:
HBP: 45° C
100% infill
Layer Height: .2
Number of shells: 1
Feedrate: 25 mm/sec
Travel Feedrate: 55

This print is so small and delicate that any extruder-induced jiggling of the Replicator is likely to shift the plastic off your platform. I got good results by slowing the print heads down. Here’s how I did it:

Generate your gCode from within ReplicatorG using the above settings. Then do a couple of find/replaces in your favorite text editor:

Replace F750.0 with F100.0
also replace F1500.0 with F100.0

There’s probably a way to do this from the GUI but for some reason I’m more comfortable mucking around in the ASCII.

Run the print. Your instinct will be to pull that new nib off the build platform and jam it into your stylus ASAP. Don’t. Give it a few minutes to cool so it doesn’t warp upon removal.

It’s easy to remove a fresh nib from a Wacom stylus. Just grab it with some pliers and pull gently. Scissors are useful for removing a worn nib; cut slightly into the plastic of the nib with the blades and then pull it out.

Download it here.

Casting about for new ideas.

I’ve been using my MakerBot to make things to make other things, and here’s my first effort: sidewalk chalk molds in the shape of Seej bloxen. Casting with plaster is a lot of sloppy fun, especially for the under-12 set.

I’m not an expert caster, but here’s what I’ve come up with to get a consistent product out of this mold.

First, liberally smear all interior surfaces of the mold with a lubricant of your choice. I used petroleum jelly, but I imagine anything greasy would work: Murphy Oil Soap, a little EVOO, liposuction byproducts, whatever you have around your workspace. This will help you remove the finished product from the mold at the end of the process.

Mix the plaster and water according to the instructions on the package, generally about 2 parts plaster to one part water. Add a little pigment and mix well. Let the plaster sit for a minute or two once it’s mixed.

Snap the two halves of the mold together and fill it about 2/3 full with plaster. Tap the mold on your work surface a few times to remove air bubbles and make sure it gets into all the corners. Fill the mold up to the bottom of the mortises, and gently insert the tenons.

A little bit of plaster will bloop out. Wipe it off, tap tap tap the mold on the work surface, and then elastic band it together.

If you’re not using any pigment, let the mold sit for about 45 minutes before removing it. If you’ve mixed some powdered paint into the plaster, let things sit for at least 90 minutes. Four hours is too much, it’ll make the bloxen difficult to get out of the mold.

While you’re waiting, call your grandma. She misses you, and you never use all your minutes anyway.

Remove the base of the mold first, and then one side. It might help to gently wedge the mold apart with a screwdriver or chisel.

Getting the bloxen out of the second half of the mold can be a little tough. I recommend tapping the mold smartly on your work surface a few times and then wiggling the block out. Putting the mortises back into the plaster bloxen might give you some leverage, too.

Then let the bloxen rest until you’re ready to use it. A day or so of resting will give you a dandy piece of sidewalk chalk.

Using the finished products for their intended purpose might mean you have to go outside for a few minutes. May cause interaction with small children, who have germs.

Temporarily discontinue use of vitamin D supplements if you frequently leave the house for extended periods of time.

Download these models for free from The Forge.