I recently bought the 5mm LED display from Sure Electronics (same datasheet as the 3mm LED display), just to see how it would work with the Wise Clock 3 board (so I can answer the questions related to this combination).
As expected, just plug the Wise Clock 3 board into the "INPUT" connector of the display (as shown in the photo below), and everything should work. Since you may not want the board to stick out, a better solution would be to connect the two using the ribbon cable provided with the display (you would need to replace the 2x8-pin female header with a a 2x8-pin male header on the Wise Clock 3 board though).
This is a huge display. I think it may be visible from 30 meters away (can you imagine Wise Clock 3 in a public plaza?!).
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