Monthly Archives: October 2016

Plutarch’s Debut is Nigh

workbench

Plutarch 1.0 is scheduled to make his party debut two days hence at J’s Halloween 2016 bash. The active duration of the party is roughly four hours. Here are my goals for Plutarch 1.0 during that time:

  • he must not fall off my shoulder
  • his head must remain attached to his body

Spontaneous decapitation has been a serious issue for this bird. His good-enough-for-prototyping attachment system might not be ready for primetime. We’ll see.

Whether his electronics work for the frightful fiesta’s duration is almost secondary.

While I celebrate the success of Plutarch 1.0’s ahead of schedule completion, I’m excited to get his successor out of the prototyping stage.

Here’s what Plutarch 2.0 looks like as of Halloween 2016. Keep in mind his deadline is 368 days in the future:

p2point0

He’s a discombobulated mess. But he’s much improved over his predecessor:

  • got 3D printed bevel gears working
  • added avoicebox with categorized, individually addressable sound calls
  • wrote a Maya-to-Arduino animation translator for the jaw movement
  • wrote a file processor that handles the WTV020SD-16P’s wonky-ass file format
  • amplified Plutarch’s speaker so he can be heard over party din
  • made a 3D printed chassis that’s modular and easy to assemble/disassemble
  • added multiple microphone inputs so that he can turn toward the loudest sound in the room
  • replaced soldered joints with connectors

Plutarch’s jaw opens and closes in sync with his sound calls. He’s got reliable, if shaky, 3-axis head movement. All of these systems mostly work, at least in isolation.

I just have to put everything together into a single, functional organism, at which point I can start working on the final challenge: his animation decision trees. Plutarch 2.0’s almost there and I’ve learned a tremendous amount about electronics and robotics over the last few months.

Unfortunately, I’ve just run into a couple of walls.

too many wires

Too many wires. Not enough space inside the body cavity for Plutarch’s y-axis servo to rotate freely. Voltage mismatch between the Pro Trinket and the voicebox and no room to cram a regulator in there.

Working in this cramped space is difficult (especially with a splinted pinky), and the microcontroller’s going to have to move to a more accessible spot. The 90┬░ connections between Plutarch’s control wires and the microcontroller are eating up way too much servo rotation room.

Complexity could be conserved by tying a couple of grounds together. Connections could be used with higher-gauge wire. Options exist, but we’re gonna need a hogshead of brain juice over the next few weeks to figure all this out. And cash. Cold, hard cash.

It pains me to buy a $13 part to fix a problem I might have forseen but when one considers that $13 is an average morning at Starbucks for some folks, the bad feels wither away. Also I take comfort in the fact that I really have no idea what I’m doing so expectations really shouldn’t be that high in the first place.

A year remains before Plutarch 2.0’s unveiling. Still much to learn.

Printing with Filabot PETG+

rex

hashtagRAWR! PETG+ Robber Rex in repose among the autumn color.

As always, things are busy here at the lab, especially with Halloween fast approaching and extensive field testing of our Stranger Things wall underway. Most of the hardware issues have been sorted out, although how well the weatherproofing holds up to twelve hours of steady October precipitation remains to be seen. Software’s never done, of course, and there’s always the matter of how we’re going to get a livestream up and running on Halloween night.

A quick review of Filabot‘s PETG+ filament is definitely in order, since the Stranger Things wall couldn’t have gone forward without it. Disclaimer: I’m not receiving any compensation for this blog post except for a free spool of filament.

What’s PETG?

Polyethylene Terephthalateco-1, 4-cylclohexylenedimethylene terephthalate. Chances are you’ve used a water bottle made out of it using traditional manufacturing methods. Filabot doesn’t advertise their filament as food-safe, although I’m pretty confident that drinking out of a PETG+ printed teacup is going to be better for you than one made from ABS.

Heads up, the ridges in FDM-printed objects can harbor nasty bacteria, so eat and drink from 3D printed vessels at your own risk.

PETG is often advertised as an alternative to ABS, and after printing with it for a month I’m convinced. Two reasons:

  1. We’ve all experienced ABS stank. I can’t detect any significant odors with a PETG print.
  2. PETG prints appear to be just as strong as ABS prints, and can be done on an unheated bed with a glue stick wipe. No acetone ABS slurry required.

As always, we recommend that use your printer in a well-ventilated space, and don’t ever drink the acetone, kids.

My daughter had some friends over for a D&D game last weekend– one of the kids’ PLA/PHA printed Dice Citadels took an unfortunate tumble from waist hight and snapped in half when it hit the floor. Of course, this is both a crisis and an opportunity.

citadel

Don’t believe that old saw about the Chinese word for crisis also containing the character for opportunity. Ain’t so, or at least it’s more complicated than that.

Unscientific test: I dropped this Citadel, fully loaded with dice, onto the same spot where the PLA/PHA citadel met its untimely demise. The PETG+ Citadel survived. Physically it just feels more robust than a PLA/PHA print with the same settings. It’s a little springier than a PLA or ABS print, like it wants to bounce.

PETG handles details well, too:

citadel closeup

PLA/PHA can be brittle, especially after a couple of months exposed to the wild. How well this PETG+ print will hold up after six months of roleplaying remains to be seen.

transparency

The filament can be fairly transparent once it’s printed. It’s ideal for LED diffusers like the bulbs in the Stranger Things wall.

You can grab this transparency test model here, btw.

Verdict: Definitely buy this filament as a replacement for old-school ABS. PETG+ is durable, low-odor, and adheres to an unheated bed with a glue-stick wipe.

Internet of Stranger Things

TLDR; I made a Stranger Things Christmas Lights wall that you can control by adding #InternetOfStrangerThings to a tweet. It’s outside my house right now, blinking. Go ahead, tweet to it.

justice

Halloween! That time of year when Makers, who, if we’re being honest, are a little odd to begin with, let their freak flags fly with electronic projects of every kind. If you’ve been keeping up with the Zhengs you’ll already know about Plutarch the pirate parrot and the Lovely and Talented Mrs. Zheng3’s Arduino-enabled Pirate Pendant, but we’ve got one more project in the hopper this season: a Christmas light wall inspired by runaway Netflix hit Stranger Things. Plus, you– yes, YOU can tweet to this wall and your tweet will appear as a eerie sequence of glowing Christmas lights outside my house.

Try it yourself! Be nice, you bastids.

Let There Be Lights

Head out into the wilds of Amazon Prime and you’ll find plenty of LED Christmas lights that might– and we must stress might— fit the requirements of this project. Point against: our crack research team was dismayed to find that most modern Christmas lights seem to be spaced between 4″ and 6″ apart, which simply will not do for an application where the letters are more widely distributed.

Also, it’s highly unlikely that your garden variety Sunday church picnic Christmas lights are individually addressable. So in theeeeeeory we could buy a roll of Christmas lights, hack them apart with a Dremel and wire cutters and hope they’re what we need, or we could just make our own. DIY is ultimately more satisfying, so to the 3D printer it is!

Filabot was kind enough to send me a free roll of PETG+ for review. This filament prints somewhere between clear and frosty white, depending on the thickness of the model’s outer walls. It’s easy enough to whip up a few dozen hollow Christmas lights bulbs in Maya. (Got access to a 3D printer? You can download these models fo’ free at the The Forge.)

bulb

We don’t need the durability or transparency of PETG for the Christmas light bases, so they’re printed in MeltInk PLA/PHA and spray-painted black. These bases screw into the bulbs and have enough empty space in the bottom to accommodate a cut-down female header for plugging and unplugging.

Organization is key to completing a project with so many little parts! There’s not a lot of space on them for labeling with proper digits, so I hashmarked each base with silver Sharpie. This will help keep the colors in the proper sequence when I string up the lights.

sockets

Recovering from Failure

Strap in, muggles. It’s going to get technical for about a few paragraphs here.

Around Christmastime last year I was working on a project where I was trying to read data from 60-odd sensors. This project ultimately cratered, and we shall refer to it in hushed tones as the Multiplexer Incident of Winter 2015. It’s mostly behind us now. Mostly.

On the plus side, I learned an awful lot about multiplexers and cabling and bought a slew of electronics and more hookup wire than I’ll ever use. We can apply those newly-gotten smarts and parts to the Stranger Things wall.

First off, for those uninitiated– WTF is a multiplexer? In this context, a multiplexer (or mux, if ye be in the know) is a doodad that reads many signals into a single channel, or distributes one signal to many destinations. This wonderfully-written post at bildr will tell you how to read from this Sparkfun mux breakout, and writing to the mux requires only a couple of small modifications to the code. We’ll be writing to this mux to light up LED’s in a specific sequence.

Of course you need a bunch of colored LED’s, also.

You don’t want to run an LED without a current limiting resistor– down that path lies a wastebasket of fried electronics. Each mux can handle up to 9 volts, but that’ll cook the LED’s right quick. Happily these colored LEDs can be handily divided up into two groups; those with an operating range of 2.0-2.2V, and those that run at 3.2-3.4V. I put one 186-ohm on the SIG pin feeding the 2.2V LED’s and a 119-ohm on the other mux running the 3.2’s.

I told you it was going to get technical for a few paragraphs.

We want these LED’s to be in a predictable Christmas-light-like order: red, green, blue, orange, pink, purple, yellow, repeat, so there’s some software mapping of mux-pin-to-LED happening in the Arduino code. Higher voltage LEDs are on the mux labelled B.

light map

Building A Wall, Except Mexico Didn’t Pay for It, I Did

The budget for this project works out to less than $100, including plywood but assuming you’ve already got a 3D printer in the basement and your time has no value.

Programming microcontrollers, navigating the Twitter API, and tying it all together with heat shrink and hope is easy. Building stable outdoor displays out of 2×4’s and plywood? That’s hard, man. Definitely out of my element here, especially since I don’t have an easy way to make miter cuts in 2×4’s.

Confession: during construction, a piece of plywood fell down and hit me in the neck.

With enough screws and construction adhesive the whole thing should hold together for a couple of weeks and hopefully not fall over onto any pint-sized stormtroopers. Here’s the finished product– hat tip to our local Sherwin Williams for the Coriander Powder color match of a laser-printed Stranger Things screenshot.

daylight

Plywood ships in a 2:1 aspect ratio, but somebody really should manufacture 16:9 sheets for those of us who occasionally cross discliplines.

The “wires” strung between the Christmas lights are black nylon rope; the actual wiring is done with hookup wire stapled to the back of the wall. I also added “@” and “#” and @Zheng3_jim to the original A-Z. (You should probably follow me on Twitter if you’re not doing so already, cause I tweet about cool Maker shizz ALL THE TIME.)

This dog’s breakfast of electronics parts are jammed into a (hopefully) waterproof Ziploc storage container attached to the back of the wall. It’s a mess back there with the breadboards and jumper wires, but should be good enough for a temporary installation. Note warning label on it to discourage tampering and/or theft.

picovolts

Sun Tzu says: appear weak when you are strong, and strong when you are weak.

Reading From Twitter

Oy. A detailed description of how to do this is beyond the scope of this post. Suffice it to say that I’m using Tweepy, OAuth, and a poorly-written Python script that you can download here. Be sure to swap out my placeholder authorization tokens with your own.

In pseudocode, here’s how this whole thing works:

loop:

read the latest 100 #InternetOfStrangerThings tweets from Twitter
pick a random tweet from the list
filter the results for harsh language
if no appropriate tweet is found, use something benign (HAPPY HALLOWEEN, JUSTICEFORBARB, etc.)
smoosh the tweet into ASCII code

loop:

send the ASCII over serial to the Arduino as bytes
map the incoming byte to a mux pin
light the appropriate LED
wait a little bit between letters

wait a little while between tweets

Presumably one of the chans or reddit will eventually catch wind of this project, so before we send any text to the Arduino it gets filtered against a text file of slurs and epithets I keep around for precisely this purpose. There are kids around, for fuck’s sake.

An old laptop sits inside, shoving sanitized data into the Arduino through a 30-foot USB cable. That’s right, the tweets are coming from INSIDE THE HOUSE.

Download the microcontroller code here for a sterling example of how not to program an Arduino.

Tweet anything you like with the hashtag #InternetOfStrangerThings and it’ll wind up on the wall if your text gets past the filters. I’ll be tweaking the code between now and Halloween to make it more responsive to input from Twitter, and if I can figure out an easy way to set up realtime video stream I’ll do that too.

Happy Halloween if I don’t talk to you sooner. Lao Zheng out.