I destroyed 3 Arduino Nanos during this project. My downfall was using an obscure voltage level shifting chip without testing it's operation first. This chip was the CD40109B that I got from Digikey. My plan was to send out 7 data bytes to 2 sets of these chips, and shift the voltage out to one seven-seg at a time with the enable pins, because at the time of ordering, we were considering having numbers on each side of the scoreboard.

After many hours of testing and verifying that I didn't make any soldering errors (and killing two Nanos), I finally decided to test one of these chips on its own (which should have been step one) . I checked over and over again to make sure my connections matched the pinout in the datasheet, and applied power to it. Once again the thing instantly burned up.

Either the pinout was incorrectly labeled, the datasheet said "top view" when it should have said "bottom view", or I am totally hopeless. All seemed possible at that point.

Luckily I had also ordered some 74LS47 BCD to seven-seg driver chips, so I threw out the other cursed ones and gave those a try. There was still hope to have this completed before the Beersbee tournament.

Oh, and how did I killed the 3rd Nano? By programming it out of the circuit with a short usb cable as it was hanging beside a metal computer case. That one was definitely my fault.