**Thank you to PCBWay for covering the cost of boards for this project**

The Engineering department where I work teaches a Microprocessors course every year, where students build a working Z80 computer. In order to visualize the addresses and data used by the Z80, we use these hex displays to turn four bits of data or address bus into a single visible hex digit. The basic idea was to replace the venerable TIL311, which has gotten quite expensive recently ($20 per digit or so.)

The board was originally designed so it could be produced on our in-house LPKF board mill, so the pads are comically large and the traces are much larger than they need to be. This is also why much of the text is dark; the LPKF process doesn't have silkscreen or solder mask, so these features were designed onto the top copper layer (which is soldermasked in PCBWay's modern process.) The next design iteration should have this fixed.

FAQ: Why common anode? ... It was what we had in stock at the time.