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Summary
"A Little Piece Of Chaos" was a means to an end. I wanted to make a free-running chaotic sculpture using LEDs and Steph was lucky enough to get her name put into lights. (Oh, and putting your girlfriend's name in lights is a way to their heart).
The video to the right will wet your appetite to read more.
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Chaos Rules
The basis for the design were red and green blinky LEDs. These are standard off-the-shelf from Digikey LEDs in a standard T-1 3/4 package with an integral resistor. Because of slight variances in the internal RC circuits, these blinky LEDs differ ever-so-slightly in their interpretation of 2Hz.
A little bit off time at a coffee shop, and the idea was hatched. At any point in a given (western) letter, you could find yourself at the end of a segment, in the middle of a segment, at a three way junction (think "T") or a four way junction (think "X"). To set up our chaotic environment, we need to establish just 2 simple rules.
RULE # 1: The endpoint of every letter segment is a blinky LED.
RULE # 2: A blinky LED can only connect to (and drive) a passive multicolor LED.
These two rules carry some interesting implications and drive the design. For instance, since no two blinky LEDs can connect, the three-way and four-way junctions must be occupied by multicolor LEDs. This also directs the number of leads required for the multicolor LEDs. For instance, along any given line segment (not at a junction), Red/Green bicolor LEDs are used. At three-way junctions, Red/Green/Blue tricolor LEDs are used. At four-way junctions....well...I never needed to figure this one out since "S-T-E-P-H" has no "X" or "K".
The above rules also drive the spacing and the number of LEDs along each segment.
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PCB Layout & Design
Since there exists no affordable and decent PCB layout program that can handle images/fonts/graphics, I have become proficient at using Adobe Illustrator as a PCB layout tool. Additionally, I have become quite proficient at burning my own PCBs in my garage.
The image to the right shows the Illustrator artwork for the final PCB. Below the board is the test board for verifying the circuit and the Chaos Rules. The font used for "Steph" is Sand.
This particular layout took several nights spread out over a month (with an equal amount of double-checking). You can also see some notes regarding voltages and required diode drops.
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PCB Fabrication
As mentioned earlier, the PCB was custom fabricated in my garage. It is a single layer board. The board comes pre-sensitized (MG Chemicals) and all one has to do is expose, develop and etch (ferric chloride). If you have ever worked in a darkroom, then PCB etching is a cakewalk (monochrome vs. grayscale).
To the right is the first attempt. You will note the glaring error due to a failure in (my own) process. The failure was to clean the glass plate prior to each exposure. I had exposed the test PCB just prior....and it shows.
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Construction
Following the PCB fabrication and parts procurment came the construction phase of the project. With a project like this, one must take it a little bit at a time. Needless to say, I got very very very good at soldering 1206-sized LED packages. I also got pretty good at surface mounting T 1-3/4 sized packages.
To the right, lots of ground wires are hanging out ready to be tied together. This was one of the downfalls with burning my own (single-layer) PCB.
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Construction (2)
Ground wires and positve-rail wires, oh my! This rats nest courtesy single-board etching in one's garage. The stainless steel standoffs have been attached.
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Construction (3)
The wires are under (quasi) control here and the back acrylic panel is attached. A fan is included to keep things cool and ensure that the LEDs last hundreds of thousands of hours.
Note the two polarized plugs. These enable the sign to be used on a desktop or mounted to a wall. Additionally, a resettable fuse is included to keep any potential shorts from completely destraoying all the hard work.
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Back Closeup
Signed, dated and clearly labeled. Sure, I could have hidden all that wonderful sky-wiring, but I believe in showing my work--even if that work is kinda messy.
Do you like that clear plastic fan body?
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Front Closeup (1)
Here is a closeup of the "E". You can see the resistor placed with each string of 5 static surface mount LEDs. Check out the surface-mounting of those leaded components!
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Front Closeup (2)....cheating
Rules are meant to be broken, right? Since the "H" was the only section to make use of the tri-color RGB LEDs, there was an imbalance of blue. This was corrected by breaking the rules and placing an RGB LED in the "S". Shown here is that rule-breaking (documented, red-handed). If you look really close you can see the ultra small diodes used to get the appropriate voltage drop.
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Finished
Completed with the front panel in place. An additional "lid" goes over the top section of the board to prevent dust from accumulating (it works well). The board was cleaned and conformal coated to prevent oxidation from eating the traces.
To provide electrons, a standard power supply from a generic PC tower was modified with a switch and appropriate connector.
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Finished (2)
Here's the side view, up close like. Flame polished acrylic (sans-scratches). I made a special front panel out of frosted acrylic (for that diffused look) but opted for the clear panel instead.
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Finished (3)
Full on frontal view.
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Finished and On
The video really does it more justice. This sign is bright enough to light up the room like a half-dozen candles. With the chaotic blinking, the room really does appear lit by warm candlelight.
Note: To the right you can see the "cheater" blue LED in the "S".
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