Wednesday, October 30, 2013

Daft Punk Helmets: Lots of Lights

Previously, I covered the construction of both of the Daft Punk helmets in a series of posts. Starting with cardstock, they were assembled with superglue, reinforced with fiberglass, molded with Bondo, painted with metallic paint, and visors were made from heated plastic. They were nice and shiny and ready to be worn.

While the black-on-metal look matches the current era of Daft Punk helmets, they haven't always been so simple. Over the years they have gone through a series of visual changes, mostly involving the embedded electronics. You can find examples of when both helmets had an unreasonable number of LEDs hidden behind the visors doing all kinds of flashy things. The silver helmet can have a red LED panel stretching across the inside of the visor with other colored lights at the ends, while the gold helmet can have rainbow blocks of color running down the sides of the visor with a large yellow LED display panel covering the center. Mimicking these elaborate setups would take far too much of my own time and money, so I decided to boil down the lights to what I thought would represent the 'core' of the display.

For the silver helmet I decided to make a 40x8 red LED panel that would hide behind the visor and display words and patterns. For the gold helmet I went with RGB strips lined up down the sides of the visor. Instead of trying to diffuse the colored lights to make a solid block of color, I went with gluing the lights right to the back of the visor to create a slightly harsher and more modern look.

I'll start with the work that went into the 40x8 red LED display, since that one was much more difficult to assemble. The first step was to decide on how to control all of the LEDs. I went with a few MAX7219 controllers, each capable of controlling a single 8x8 LED panel. To prototype the controller, I set up a spare Arduino and pre-made LED panel:

Thanks to numerous examples found online of how to interface with the controller, I set off assembling the red LED panels. Since the display would sit right in front of my eyes inside the helmet, I needed the panel to have enough empty space between LEDs in order to allow me to still see out. To do this I set up a grid of holes in some cardboard and used it as a frame to solder the LEDs together. I made 5 8x8 panels where each column had common cathodes and every row had common anodes.

After quite a few hours of soldering, I had all of the LEDs soldered into panels. I wanted the LED drivers to sit on their own small protoboards near the panels.

With every 8x8 panel connected to a driver, I was able to hot glue all of the panels together side-by-side to make the single large display. I put little wooden sticks at the joints of each panel to allow the panel to be glued into the helmet without having to secure the LEDs themselves to the helmet.

Since the drivers could all be daisy-chained together, there were only 5 wires needed to fully control the panel. Two for power, one as a clock, one as a latch, and one as a data line. These would be hooked up to an Arduino controller, but more on that in a later post.

The lights for the gold helmet were someone easier once I decided to buy an addressable RGB LED strip from ebay. The one I picked was 144 LEDs crammed into a single meter with a built-in driver on each LED. As long as every LED was daisy-chained, only one data line was needed to set every LED to a unique color. I cut the strip into segments that were 6 LEDs long and re-soldered them back into a chain with wires to space them out.

This way, I could orient the strips to run parallel by bending each wire segment by 180 degrees, yet still only use a single data wire to control them all.
Since the LED drivers were all on-board, I was able to test the LEDs at many stages of the assembly.

The first thing I really realized was how bright the strip could get. With every RGB LED running at full brightness, the helmet would pull over 5A of current just to light it up. I was looking for a colorfully lit helmet, not a head-mounted search beacon. I decided the best way to solve this was in software, so I just kept the brightness in mind while testing the hardware. I marked off on the visor where the lights needed to be glued and went to work.

With all of the strips attached, I hooked up the power and data lines to a testing Arduino and lit it up.

At this point, both helmets had lights installed and ready to be driven. The end of the project was in sight, with only the control electronics, power source, and coding to sort out. Once again, more on that later.


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