Beacon3

Beacon3 will be a beacon for the top of our flag(less) pole for Burning Man 2011. It will be simpler than Beacon2 as time is limited to get it done, but we want a brighter beacon.

Ideas

• Beacon Unit
  • Less LEDs, but much much brighter. Thinking either a triangle or square with a 1, 3, or 5W RGB LED (either integrated or discrete) on each side.
  • Using RGBW LEDs would add extra driver circuitry, but would mean we could do white for 1/3 the current draw of using RGB LEDs
  • Planar PCB that fits onto the spindle, then LED PCBs that plug in vertically seems like it would work
    • LED PCBs may need heat sinks, which could fit into the middle space around the spindle
    • LED PCBs would have all required LED driver circuitry on them
      • 4x NXP SSL3520A chips on each board looks good to drive the RGBW LEDs (500mA per component colour)
        • This chip has a fixed I2C address though so an I2C mux would be needed on each LED board, plus one on the planar
          • The PCA9545 looks perfect for this, I2C controlled 4:1 I2C mux
  • Single MCU this time, as there are fewer LEDs
    • An ATmega328p might work if the pin count required is low enough, would make programming for it easy!
  • Same enclosure as Beacon2 can be used to save time, just remove PCBs and replace with these
  • Same light sensor and (lack of) charging circuitry as Beacon2 can also be used
  • Regulator will be on planar, needs to be 3* whatever LED current we go with for triangle, or 4x for square
    • Do we even need a regulator other than for the Xbee? the LED drivers may do their own regulation?
    • This allows for one LED on each side, or all LEDs on one side, or any combination of that to be on at one time
    • LDO may be the most efficient given the small in->out difference, need to calculate the efficiency of each option
• Remote Control Unit
  • Having a remote that would make the beacon extra-noticeable when a button was pressed would be cool
  • To get long enough range to be useful, we'd want ~50mW
  • XBee is probably the best way to go, but need to look at power draw for the RX side and would have to custom-design a remote control unit
  • Remote Control Unit could just be:
    • Arduino Fio
    • XBee Series 1 RP-SMA (plugs directly into Arduino Fio)
    • Rubber-duck antenna
    • LiIon pack (plugs directly into Arduino Fio)

Project Status

2011-07-19: Initial design started.