Module specifications
Every number you need to plan a display, get a case built, or hand to whoever signs off on an installation. If something's missing, ask on Discord or by mail and I'll add it.
Mechanical
| Value | |
|---|---|
| Module front face | 116 × 60 mm |
| Weight per module | ~400 g (metal case, NEMA17) |
| Flap size | 44 × 30 mm, plus material for the hinges |
| Flap thickness | 0.3–0.6 mm |
| Mounting | 3 screw holes on the back of the case |
| Motor | 28BYJ-48 (5 V) or NEMA17 17HS08-1004S, 20 mm height, lead-only |
The flap dimensions aren't negotiable. The entire mechanical design is built around them. Everything else scales.
Flaps per module
| Value | |
|---|---|
| Standard alphabet | 43 characters |
| Minimum, for reliable operation | ~30 flaps |
| Maximum tested | 52 flaps |
The lower bound catches people out. The topmost flap needs pre-tension to fall cleanly, and that pre-tension comes partly from the other flaps being there. Below roughly 30 flaps the mechanism gets unreliable, so if you only need six colours or ten characters, repeat the set until you're above 30 rather than leaving the drum half empty.
52 is the highest number I've built and tested. It can probably be pushed a little further.
Electrical
| Value | |
|---|---|
| Supply voltage | 12 V DC |
| Current draw per module | up to 500 mA under load |
| Maximum current per power group | 3 A |
| Modules per power group | 5 (one injector board every 5 modules) |
| Protection | Reverse polarity; TI eFuse per injector board (over-/undervoltage, short circuit, overcurrent) |
| Linking boards | Connection board, power break, injector board (details) |
A single 12 V / 30 A supply, injected at six points, comfortably runs about 30 modules. The calculator does this arithmetic for any display size.
Thermal & environment
| Value | |
|---|---|
| Maximum module temperature | 38 °C under continuous heavy use |
| Ventilation slots | Not required |
| Recommended clearance above modules | 3–5 mm |
I've run modules through long endurance tests and they never got past 38 °C, so no active cooling and no ventilation cutouts are needed. What to avoid is a fully sealed cavity behind the display where warm air has nowhere to go. Leaving 3 to 5 mm above the modules is enough for it to escape.
Control
| Value | |
|---|---|
| Controller | ESP8266, one per module, all modules identical |
| Wireless | WiFi, one entry point per signal chain |
| Wired | Serial daisy chain, TX of module N → RX of module N+1 |
| Addressing | Relative position in the chain: N:COMMAND:ARGUMENT, @ for all |
| Firmware | Pre-flashed, configured in a browser |
There's no separate master or controller unit to buy. Every module has the same board, and the first module in a chain is just the one that talks to WiFi and forwards commands to the rest. Electronics has the protocol, Wiring & Power has how signal and power run through a display.