I decided to find out how large a 4-digit LED display I could fit into a budget 100x100 mm PCB, and how much it would cost, so that I can make future projects with large digits.

LED displays, with or without driver chips onboard, are cheap these days. But the usual offerings are in small sizes, e.g. 0.36 in, 0.56 in. Even back in the days of abysmal LED efficiency, I had 20 mm tall digits. You can of course buy large digits. They are more likely to be single digit displays as the size increases. Perhaps the yield goes down when combining digits. But using multiple packages in multiplexing is not a problem if you have a PCB to take care of wiring all the segments together.

The quest

It was about the time that I was checking out LCSC. To make the shipping an acceptable fraction of the total cost I had to make a large order.

The ARKLED SM411006N/15 1 in red display is cheap at $0.25 (all prices in USD).

The TM1637 driver chip is only $0.15. It comes in a SOP20 package that will give you practice with soldering SMT.

...

Further details at Hackaday.

https://hackaday.io/project/169179-inch-digitsHackaday