On January 31, 2007 Boston was shutdown when pieces of LED artwork that looked like characters from the Cartoon Network show Aqua Teen Hunger Force were mistaken for bombs. Ever since this occurred I have wanted to build my own version to hang up in my apartment.
My version is designed to look like the character Ignignokt; in case you don’t watch the show Ignignokt and Err (his sidekick) are Mooninites (residents of the moon, designed to look like characters from an 8 bit video game) who occasionally come down to Earth to annoy the Aqua Teens. I chose Ignignokt because he is green and blue (Err is purple and blue) and green LEDs are cheaper than purple LEDs. My design used 72 green and 40 blue LEDs.
I got my LEDs from Mouser and I chose them based primarily on their diffusion angle (over 40 degrees), which allows for better viewing angles than other LEDs. In order for an LED array like this to function properly the LEDs must be wired in parallel (ie. all of the cathodes are connected together as well as all of the anodes). I also had to subdivide the LEDs into a group of all of the green LEDs (D6 on the schematic) and all of the blue LEDs (D5 on the schematic). This had to be done because the LEDs were different types and there were more greens than blues, causing the current draw of the groups to be unbalanced. This created a problem where only the green group would light, consequently, I adjusted the resistor values such that I balanced the current drawn by both LED groups. There are also four additional groups to create the effect of Ignignokt giving the finger. These groups are controlled by a PIC16F84A microcontroller which orchestrates the animation of the LEDs. As shown in the schematic, group D1 is the hand and groups D2-D4 are the finger. The code (written in PicBasic) is very simple, involving only turning on specific digital outputs of the PIC for set periods of time. I can power the whole thing off a 9 Volt battery using a power circuit similar to that shown in the schematic for my GPS project (I substituted a 78L05 for the 7805 voltage regulator since this circuit draws less current). Check out the video to see Ignignokt in action.