Why be so public about something so secret? Because this tile uses a layout technique that lets you build charlie-plexed LED arrays quickly and cheaply — and that’s something worth sharing.

Charlie Tile Circuit

You need to flip the tile over in order to see what’s special about it. Here’s a quick list of features that make the assembly what it is:

• The back of the tile has six “column” conductors and six “row” conductors.
• These column and row conductors are connected along the diagonal of the row/column array.  At all other points in the matrix, the row and column conductors are isolated via a layer of masking tape.
• LEDs above the diagonal have their cathode connected to the conductive row immediately above the LED.  LEDs on or below the diagonal have their cathode connected to the conductive row immediately below the LED.
• All LEDs have their anode connected to the column that is to their immediate left.

The resulting circuit allows you to individually address any of the thirty LEDs in this 5×6 matrix using only six lines from a micro-controller.

It turns out that this assembly technique is pretty quick.  It’s also physically robust.  Best of all, it’s cost effective — copper tape is relatively inexpensive and masking tape is downright cheap.  To get some perspective on how this compares to other assembly techniques cost-wise, go price a custom printed  4.5″ x 5.25″ circuit board.

This technique can be used to assemble arbitrarily large tiles.  In fact, the larger the tile, the more effective the technique is with regard to saving time and money.  And, as a fortunate coincidence, most peg-boards happen have 5mm holes — so that means you buy the peg-board at the hardware store and jam LEDs in there perfectly w/o any drilling whatsoever — so just buy the panel, tape it up, jam in the LEDs, solder the leads and enjoy the show …

Tuesday – DIY Music Night

Wednesday – Open House

Thursday – Game Night Featuring Tetris Arm Wrestling Tournament

Friday – PTW Gala demonstration (offsite)

Events at Hive76 Monday through Thursday start at 7pm and 

ARE OPEN TO THE PUBLIC.

Friday Gala Ticketing information available here.

Back-lit view of paper and foil micro-controller board

After visiting The Hacktory’s “Soft Circuit” event, PJ and I were inspired to take a stab at making some micro-controller circuits using alternative, “high/low tech” approaches.  PJ made an MCU circuit using conductive paint (has potential, but needs some tweaks).  I opted to try a circuit board using metal leaf.  That happened to work on the first shot — although careful scrutiny of the picture on the left suggests there was some luck involved (there are holes in the circuit that come dangerously close to wrecking it).

Looks good from this angle and all the connections check -- you'd never guess it was hanging by a thread ...

I had considered using scored foil as a way to make free-hand, one-off circuit boards for quite some time — but until recently, I never had the mix of free time and raw nerve to actually try it.  It turns out that my reservations were probably well-founded, but it also happens that the technique is workable, and the results are actually aesthetically interesting.

We decided to make the board in a hexagonal shape (Hive76 — hexagon — get it?). First, we prepped circuit board material by spraying adhesive on card-stock and then sticking the faux gold-leaf on the prepared surface (this sounds simple, but the foil is maddening stuff, so the process involved profanity and a certain amount of despair).  Then we cut the foiled card-stock into hexagons. After that, we cut out a rectangle where the IC was going to go, so that there were no conductive paths under the chip.  Once the board was roughly prepped, we made a “squashed bug” of the IC , splayed its pins out, and soldered it to the gilded surface.  Using the gaps between the pins as a guide for an exacto knife, we cut free-hand traces that routed the pins of the chip to large zones on the edge of the hexagon (I was a little surprised that the cuts were free of bridges). Finally, we soldered a capacitor between the MCU’s Vcc and ground and soldered a 47k resistor between Vcc and the MCU’s reset line.  At that point, we had a working circuit that was in-system programmable — at least in theory.

Unfortunately, I had no idea how we might program the MCU or hook it up to external circuitry without damaging the fragile structure.  PJ came up with the idea that made it all workable … magnets.  All really good magic is done with magnets.  The idea here was to place the paper computer on a steel surface, which allowed us to stick magnets wherever we wanted to make a connection.  With steel under the circuit, the down-force of the magnets gave us firm-but-gentle electrical contact with the delicate foil. Once the magnets were in place, we only needed to touch alligator clips to them — since the clips were steel, they stuck happily. With the clips secured to selected points on the MCU, we were free to connect the opposite ends of the clips to the various external items needed for the circuit.  Note the ingenious use of paper-clips.  PJ again — see a pattern here?

Our first connection was power (two magnet connections, one for +3.6 volts, the other for ground).  Then we hooked up the Spy-bi-wire programming interface (two wires, two more magnets).  After that, we wrote the obligatory “blink LED” program and loaded it into the paper computer.  Naturally, we wanted to see the results — two more connections for the LED terminals and — Voila!  Here’s the movie …

To begin with, it has node.js baked right into its Ångström Linux OS.  This node.js installation is extended with a “Wiring-like” API.  Then add the fact that BB “sketches” (for lack of a better term) are edited right in your favorite browser, using the Cloud9 IDE.  Cloud9 is clean and simple and it supports the essential IDE features that you might expect — a decent editor with code colorization, management of the files that comprise a project, an interactive debugger etc.  The idea of a web-enabled physical computing platform that is itself programmed using a web interface seems so obvious and so “right” that it feels like it was always meant to be.   Pure elegance meets sheer genius.

At any rate, the fact that this puppy is an outstanding physical computing platform with righteous networking capabilities makes it about the perfect platform for Internet Of Things architectures, so that’s where I’m focusing for now.

Since I have a background in process control systems and a bit of a bias towards Philly-grown tech,  I settled on NimBits for my back-end.  It has all the attributes of a real process control historian with a cloud architecture and some nice bells and whistles to boot.  Since NimBits counts an XMPP based API among its various access methods, I wrote a little study to see if I could send IMs using node.js.  Turns out it’s incredibly simple (check out the picture)  This app doesn’t push stuff to NimBits (yet), but it’s only a half-step away from it — and being able to have a physical computing platform send you IMs is pretty darn useful in its own right.

Keep an eye out here for more Beagle Bone and Internet Of Things stuff.  We live in fascinating times!

We whipped up a Wiring-ish wrapper for the MSP430 a while back in order to simplify the task of porting Arduino libraries for use with MSP430 microcontrollers.  It turns out, we weren’t the only ones that thought of it.  PJ spotted a post on Hack A Day where someone unveiled something remarkably similar, and that post resulted in at least two other folks besides us posting their similar ideas — so there are at least four of these wrapper libraries out there.

Naturally, we’d like to think that ours is the best of the bunch, and the best named too — TIWrap.  Seriously, though, we seem to be genuinely different in that that we have bundled in actual libraries ported from Arduino, such as the HD44780 and MAX7221 libraries.  There are some piezo buzzer libraries and we expect to add some Charlieplexing utilities soon.  You can get a copy of TiWrap here.

The demo above is a “Fancy Flashlight” concept proposed by Matt Torbin.   It’s just one MSP430, two LEDs, a button and a bit of code which you can find in the TiWrap examples.

And in case the title left you puzzled …

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It was weird to hit the Wednesday Hive Open House and see a handful of original MSP430 projects.  The video above is an LED chaser effect that Chris Thompson whipped up based on concepts from the first session of the MSP430 class.  As the old saying goes — teach a geek to fish and you’ll soon have LED encrusted fish.

Speaking of LEDs, here’s a Morse Code blinker project that Chris did.  Mostly a cut & paste job, but if nothing else, it makes the point that there are plenty of  MSP430 code samples out there and that it’s relatively easy to use them once you know the tools.

Audience

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