Bus side flip-dot display

In Lithuanian flip-dot displays are mainly used in public transport. This is due to that flip-disks use no power except in transitions and are visible even on the brightest of days. Usually every bus is usually equipped with front, side (see above) and back display units (for more information about flip-dot displays visit my Lituanian blog at: http://paulius.bautrenas.lt/blog/elektromechanines-svieslentes)

Disassembled 16x28  flip-dot display

For this project I repurposed a small "side" display (see above) and build a custom controller for it. AtMEGA16 is used as a central processor and a battery backed DS1307 real time clock provides timekeeping.

The circuit is assembled on a home etched and hand drilled PCB. Everything is ghetto mounted inside clock case. Display was already equipped with white CCFL backlight, which requires +24V DC power supply. CCFL was a bit to bright for a indoor use, so I added an extra UV LED strip. To power LED strip and a main controller I use 12V DC/DC module from Aliexpress. Both CCFL and LED strip is controlled via 2 N-Fets, mounted on a separate board

CCFL backlight
UV backlight

Initially clock was controlled via 2 push buttons, but later on I added a HC05 module which allowed to set time and control clock back-light via Bluetooth. After discovering how much DS1307 drifts over time, I organized periodic NTP like clock synchronization via Bluetooth with my RPI (https://github.com/pauliusbau/raspberrypi-mayhem/tree/master/RPI-bluetoothTimeSynch)

Flip-Dot clock control via USART
Time synch via Bluetooth with RPI

More info about flip-dot displays and flip-dot clock can be found on my Lithuanian and GitHub:

  1. Detail flip-dot display operation analysis: http://paulius.bautrenas.lt/blog/elektromechanines-svieslentes
  2. Flip-dot clock build: http://paulius.bautrenas.lt/blog/flip-dot-clock
  3. Flip-dot clock controller source code (spaghetti style): https://github.com/pauliusbau/electronics-farm/tree/master/Flip-Dot%20Clock
  4. Bluetooth communication between flip-dot clock and RPI: http://paulius.bautrenas.lt/blog/flip-dot-clock-laiko-sinchronizavimas-su-aviete-per-bluetooth/
  5. Python scrip for automatic Bluetooth time synchronization: https://github.com/pauliusbau/raspberrypi-mayhem/tree/master/RPI-bluetoothTimeSynch