Please see my blog post for full details and other files.

• A single microcontroller board is connected to 3 smaller driver PCBs, each of which controls 4 characters.
• Cost for the bare PCBs is $10 (from PCBWay), plus shipping. In fact, you get more than enough PCBs to be able build 3 of these 12-character displays.
• Off-the-shelf ribbon cables are used between PCBs to reduce custom wiring.
• All components are through-hole mounted (i.e. no SMD).

The files attached here are for the mounting brackets for the PCBs, as they no longer are attached to the back of the unit frames.

Additionally, I remixed the unit frame to:

1. strengthen the motor mountings,
2. attach each unit to the next (not relying on an outer cover to do so), and
3. better accommodate my replacement 3.3V hall-effect sensors.

However, note that this remixed unit frame is optional as this alternate electronics should be compatible with the original frame design.

This remix will not suit everyone:

• This is aimed at those planning to make their own enclosure. PCBs are not mounted to the back of the display units but have their own brackets to attach directly to the case. 
• A display having greater than 12 characters would require an additional controller board and decisions on how to manage that. The original design can accommodate up to 16 characters without any changes.