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Mk3 Steampunk Goggles
Project Details ]
Posted by Krux on Monday October 7, 2013 @ 01:53pm
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The Mk3 Steampunk Goggles are the next evolution of the goggle design.
Improvements are:

  • AVR based microcontroller
  • All surface mount components
  • RGB LEDs
  • PWM LED driver chips
  • Modular design


  • Initially my design was going to use the Texas Instruments TLC5941, 16-channel LED driver. It's was nice chip, small, and does PWM using SPI. The design lets you change multiple driver boards together, so only a few pins on the microcontroller are required to drive the LEDs. However after prototyping the design, it turned out to required seven wires between boards, and had a hard time fitting into the space I was allowing. I managed to get a prototype working, but running three boards per eye piece wasn't going to work.

    http://youtu.be/ezeFfVcE8FA
    http://www.youtube.com/watch?v=zsrGT5LSr1o


    Doing some more research, I found the NXP PCA9685 chip, which is a 16-channel, 12-bit PWM Fm+ I2C-bus LED controller. With this chip I did have to add a resistor for each LED channel, since it didn't have the constant-current sinking capability of the TLC5941. But reducing the number of wires required to drive the board, made it much simpler of a board layout, so the added resistors for each LED channel ended up not being an issue. After a couple respins of the board design, I had a working design.



    Once nice thing about the board, is it was designed to be modular. My Mk2 goggles had one eye piece that had LEDs in 1/3rd of the ring, and one eye piece that had LEDs in 2/3rds of the ring. So this updated design allows for that. And as a bonus, the boards when assembled in a full ring are a perfect press fit in the goggles. This means no additional mounting hardware or adhesives are required to keep them in place.

    Here is video showing the finished build, with the added metal embellishments:


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