A Clock Built from Scraps


Who doesn’t love a good surplus store? [Tyler Bletsch] just finished up this awesome clock hack by re-purposing a scrapped medical circuit board.

Ax-Man Surplus in Minneapolis has all kinds of goodies and it’s been around a long time (here’s a hack from the ’90s that source from the store). One day while digging through their inventory, [Tyler] found a bunch of scrap circuit boards with 7-segment displays. At $2 a pop, he decided to risk it to tinker with.

He quickly identified the main chip on the board to be a common LED driver (MAX7221) and began reverse engineering the board by tracing the circuit. He actually has a brilliant guide on his website about how to make circuit tracing way easier. From there it was just a matter of loading a MAX7221 library onto a ATtiny44, adding a 16MHz crystal, and since there’s an extra 2 digits available on the display… a temperature sensor too!

It’s a great little hack, and as it turned out, there wasn’t anything wrong with the boards, except for a minor typo in the company’s name. Hooray for reusing scrapped parts!

5 thoughts on “A Clock Built from Scraps

  1. Not to be nit-picky but there are no ax-man stores in Minneapolis. The all time best one is in Saint Paul MN. Ah, yes we so often get lumped in with our neighbor to the west! AXMAN RULES!

  2. nice
    please help me , i want to connect DHT11 sensor for humidity & temperature mesurements to arduino board and i want the cood to run and gets results . thank you

  3. They have stickers and magnets by the checkout, “Built with genuine ax-man parts”. I have a magnet on my toolbox, and always threatened to put one on my airplane.

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