2011 Halloween - Making Mr. Bubbles
Not really appropriate for here except for the electronics I used to add sound and light control for the costume.
I used a "Leg Controller" board from my polyPod project to produce the audio and to control the high intensity LEDs for the costume. The dsPIC33 on the board has audio DACs. I'd never heard of these before so was quite pleased to learn how they work. Unlike a regular DAC which takes the given value and outputs an appropriate voltage the audio DAC applies automatic 256x oversampling. In this case I supply the audio DAC with a 3KHz signal that I've stored in program flash ram. The audio DAC outputs 256 x 3 = 768KHz waveform. Of course the DAC can't add information that's not there but at least it can smooth out the coarse 3KHz steps.
In the code I've written, the data is being retrieved via an interrupt. Each interrupt reads the next audio value. If the interrupt can't be serviced in time the DAC has a 'default' value that it will use in its place. The DAC can also work via DMA although I haven't explored that. This would presumably lower the load on the processor allowing much higher sample rates to be supported.
Altogether I have about 10 seconds of 3KHz 8bit audio. Not much but enough for a passive moan and an angry roar. The processor has more Flash ram available but by keeping it to 32K in size I can embed the audio into my program as a CONST array.
The weak DAC signal is fed to a disemboweled amplified PC speaker. The LED control is nothing special, just two signal lines to two NPN transistors to turn the green and red LEDs on or off.
Most of the time went into 'sculpting' the intricate cardboard body. The main cost was two rolls of red 'Tuck' tape at $10 a piece and several cans of spray paint. The cardboard was all from the recycle bin and the PC speakers from the local e-waste recycle dock. The "leg controller" cost was about $8 being mainly the cost of the dsPIC. I still have about 50 blank PCBs that I will probably never use up.