DIY Punch Card System Despite Hanging Chads

Sometimes you just have parts lying around and want to make something out of them. [Tymkrs] had a robot paper cutter, so naturally they made punch cards. But then, of course, they needed a punch card reader, so they made one of those too. All with stuff lying around the shop.

The Silhouette Portrait paper cutter is meant for scrapbooking, but what evokes memories of the past more than punchcards? To cut out their data, rather than cute kittens or flowers, they wrote some custom code to turn ASCII characters into rows of dots. And the cards are done — you just have to clean up the holes that didn’t completely cut. These are infamously known as hanging chads.

The reader is made up of a block of wood, with a gap for the cards and perpendicular holes drilled for LEDs and photoresistors. This is cabled to a Propeller dev board with some simple firmware. We would have used photodiodes or phototransistors, because that’s what’s in our junk box (and because they have faster reaction time), but when you’ve got lemons, make lemonade.

OK, now that you’ve got a punch card reader and writer, what do you do with it? Password storage comes to mind.

7 thoughts on “DIY Punch Card System Despite Hanging Chads

  1. I had an old Intel PROM programmer from the 70s that I picked up (long story) that programmed the PROM chips from a punched paper tape. The sensor was a row of small (3mm x 3mm) solar cells with a long halogen tube opposite them. The tape fed between them. It really amazed me how fast the tape was able to run, even with such a slow sensor as a solar cell…

    The other related story that I have is that when I worked at Atomic Energy of Canada up in northern Ontario during the summers as an undergrad, the campus library used old Fortran punch cards as library slips. We always would decode our slips do see what programming statement (or operand) we had been given :)

  2. A good application for this would be cost-effective security cards. A card with holes in it will always be cheaper than a magnetic swipe card or a near field card, plus, this can’t be sniffed.

    1. But much easier to copy. For low level security or novelty use it would be fine.

      Could be a great exhibit at a science museum where kids can get their name “printed” on a punch card and have it read by a device on display.

      1. That is a really cute idea! I was toying with the idea of having it for each of our hackerspace members. 5 points for coming, 100 points for cleaning something :p. Then they could redeem it at the end of the year for oriental trading erasers haha.

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