Tuesday, January 23, 2007
Le signe est fait. Translation... "sure took me long enough."
The "Bar Sign" project is finally complete. I think my sister liked it although I did see some gaps in her enthusiasm during the unveiling. I believe they were failed attempts at comprehending my fascination with LED's. She was right to be confused, a tiny blinking light can only giddify the most stout of geeks. I hope she enjoys looking at it as much as I enjoyed building it.
Speaking of construction, allow me to front you some details. The black wooden shadow box frame measures in at around 20"x8" and holds two pieces of hand etched Plexiglas panes illuminated by six tri-colored (RGB) high intensity LED's. Quite a mouthful huh? That's not the fun part. To drive all the the color combinations possible, I used a Microchip PIC16F676 microcontroller and a Maxim MAX6957 LED driver to do all my dirty work. I'm still trying to decide why I wrote the firmware in assembly. Sometimes those things harder to do aren't always worth doing.
This is what the guts of the project look like. Not the prettiest of designs out there but it could have looked worse if not for using plain ol phone wire to hook up the lights. Its four conductors were perfect for each four-lead LED.
Want some theory? I'll let Wikipedia handle the bulk of the work for me. In a nutshell, I vary the intensity of red, green, and blue light to create any color I want. I direct that light through the side of each pane of Plexiglas and it escapes only where I have etched it. I didn't go too crazy with the lighting programs. I only wrote five and they can be cycled through by pushing a button on the side of the frame. I also included a control knob so you can pick your own color if the appropriate program is selected. But enough of this talk, here are some pictures and a video.