Wednesday, July 24, 2013

If I Only Had a Brain

Among the things that got cut from "The Wiz" before they were installed -- but not before I had spent money and time on them -- was lights in the TINMAN.

Artistically, this is a good choice.  It would have been fun to have lights in him, but the costume works fine without.  And it is less for the actor and the stage crew to deal with.  I'm all about what makes dramatic sense, and what makes sense from a "whole theater" perspective (weigh the cost of doing the effect against how much the audience will appreciate it).

Oh, look -- more context-free pictures of circuit boards!

This was the TINMAN's brain.  Re-using once again the minimal Arduino I'd built on Adafruit perma-proto board, with ISP header for programming, 7805-based power regulator, and a ULN2803 Darlington array for switching banks of LEDs.

The program was another iteration of the pseudo-RTOS I've been doing of late within the Arduino environment; a master system counter, and timed events triggered at mathematical fractions of the counter value rather than via delay() commands.

The button was a black-out button that toggled all the costume lights off.   The ribbon cable was to drive LEDs in several different states; constant on, slow blink, fast blink (in a pattern-of-four), and pulse (power button style).  Only the PWM of the latter leveraged the internal timers and interrupts of the ATmega328p chip.

The most complex part of the code was the boot sequence.  Since this was never in an Arduino, there is no bootloader on the chip.  Instead it enters with no perceptible delay into a program cycle that only runs once (and can still be interrupted at any moment by hitting the "blackout" toggle.)

That program turns on the various LEDs in sequence, flickering several of them as it does so, to mimic a power-up sequence.  The intent was to trigger this as the TINMAN is "oiled" and would reflect him coming back to full activity.

The EASY part would have been to run that ribbon cable up the costume and to the various LEDs that were already embedded in the various found electronics and e-waste adorning it (including dead proto-boards built long ago by both me and my dad!)

But that's the point at which it was decided (and properly so) not to light the TINMAN.

And, really, the only legacy of the TINMAN lights is the two rolls of light pipe I had already bought by the time it was cut, which found their way into the WIZ's costume instead:

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