Step 7: Follow Up

After letting the controller circuit sit in the breadboard for months I finally designed and etched a few circuit boards to put this prototype together. Everything worked out great, I don't think there's anything I would have done differently.

Circuit Board Features

  • Shift registers are on separate boards that can be daisy chained together to increase the size of the display.
  • Controller board has it's own power regulator so this can be run by any power source that provides 7v-30v (9v battery or 12v bench supply both work just fine for me).
  • 6 pin ISP header included so the microcontroller can be reprogrammed without removing it from the board.
  • 4-pin header available for future use of the I2C bus. This could be used for an eeprom to store more messages or even to make this a slave device controlled by another microcontroller (RSS ticker anyone?)
  • 3 momentary push buttons are included in the design. I may tweak the firmware in the future to include the use of these buttons.


Give me plexiglass, angle brackets, 6x32 machine screws, nuts, and washers, as well as a tap set to thread holes and I can create anything.
fredkylam1 year ago

The column driver is drive only ONE column at any one time, so the current load should not be more than 8 X 15 mA or 120 mA. It seems that one driver should suffice to drive any number of columns. Is this correct?