This was a simple project to create a cheap circular LED display.
It uses 16 LED matrix displays with driver chips, these are available as a kit from places such as eBay for about £1 each. Just search for the driver chip MAX7219.
Step 1: Solder and Connect the Displays
The displays normally come as a kit and will need to be soldered together, when you have 16 built they need to be connected together in a chain.
The output of one display goes into the input of the next. Its a good idea to connect one display at a time and test it, this ensures you catch any problems early on. The displays can be driven using an Arduino and the library Max72xxPanel
Step 2: 3D Print the Display Brackets
The display brackets need to be printed, these hold the displays and allow them to be attached in a ring.
Depending on the accuracy of your printer you might find the displays are loose or have a snug fit, either way I would recommend gluing them into place. I used hot glue for mine.
The plans for the 3d printed parts can be found on Thingiverse.
Step 3: Attaching Everything Together
Once the displays are soldered up and fitted in the plastic mounts its time to start attaching everything together.
The small clips (also on Thingiverse) can be used to join the mounting holes on the adjacent displays, these won't stay in on their own so more hot glue will be needed.
This mounting option may be sufficient but for extra security I also used the flat plates to bolt between each display. The spacing between the holes on these clips is very specific, if you want to use more or less than 16 displays you can't use these brackets.
I would recommend attaching the displays together in groups of 3 or 4, this will make it easier as you come to the end.
Step 4: Mounting the Controller
This step is optional but if you want to keep the Arduino out the way you can attach the top plate and bolt it to the top or bottom of the circle.