Paper Tape Reader Self-calibrates, Speaks USB

Input devices consisting of optical readers for punched paper tape have been around since the earliest days of computing, so why stop now? [Jürgen]’s Paper Tape Reader project connects to any modern computer over USB, acting like a serial communications device. Thanks to the device’s automatic calibration, it works with a variety of paper materials. As for reading speed, it’s pretty much only limited to how fast one can pull tape through without damaging it.

Stacked 1.6 mm PCBs act as an enclosure, of sorts.

While [Jürgen]’s device uses LEDs and phototransistors to detect the presence or absence of punched holes, it doesn’t rely on hardware calibration. Instead, the device takes analog readings of each phototransistor, and uses software-adjusted thresholds to differentiate ones from zeros. This allows it to easily deal with a wide variety of tape types and colors, even working with translucent materials. Reading 500 characters per second isn’t a problem if the device has had a chance to calibrate.

Interested in making your own? The build section of the project has all the design files; it uses only through-hole components, and since the device is constructed from a stack of 1.6 mm thick PCBs, there’s no separate enclosure needed.

Paper tape and readers have a certain charm to them. Cyphercon 4.0 badges featured tape readers, and we’ve even seen the unusual approach of encoding an I2C byte stream directly onto tape.

16 thoughts on “Paper Tape Reader Self-calibrates, Speaks USB

    1. Before colossus, I think it was heath Robinson that read punch tape, from memory I think it was around 2000 or 5000 chars per second, breaking tape was the main problem.

  1. *5000cps* (53mph) was used in the early *1940s*, in Colossus. The tape tended to stretch a little. https://en.wikipedia.org/wiki/Colossus_computer

    1000cps used to be standard in the 70s, stopping and starting instantly. The paper tape on a 6inch reel was pulled through the reader by a grip wheel. It flew 6ft across the room, and landed in a 6ft by 3ft by 3ft bucket. It was then respooled by hand.

    Yes, you kept you hand out of the way, lest you sustain an enormous paper cut!

    Punching tape was much slower, unsurprisingly.

  2. In grad school we had a teletype; as most of you know it was slow as blazes. The spool of paper tape used to load BASIC (I think) took over an hour to load to the computer—I think it was an Altair 8800. The prof built a device just like the one shown here but bigger (of course! After all, it was 1979). He would pull the tape through the reader while two students kept it feeding smoothly on the other side. Took about a minute. Then…Lunar Lander! :-)

    1. There was at least one commercial tape reader back then that was standalone and cheap. 8 sensors, I think some schmidt triggers, and of course the mechanics to keep the tape straight as you pulled it through.

      There was a brief time when paper tape was used for distribution. A cheap small reader was fine, since you yourself weren’t punching tapes.

  3. Since we are on the subject, where does one get blank paper tape? (I mean aside from the eBay russian stuff) or has anyone come up with a good way to make it or derive it?

    I have a punch, I was going to do a little side gig punching paper tape for people but I’m limited to cash register tape which works but doesn’t have the desired authenticity.

  4. I was going to mention Western Numerical Control out of Phoenix AZ, but I haven’t used them for a few years (since maybe 2016?) and their website seems to be defunct.

    Ebay shows a fair number of listings in paper and mylar, and I would be unsurprised if 1″ polyester NC tape is available via one or another of the indusrial suppliers- they can be VERY creative in sourcing non-catalog items.

    (Still have a roll or two on the shelf, but I’m not letting it go. I think I still have a manual correction punch in storage, too)

      1. I was thinking about tyvek. On the one hand it would really cool and probably bulletproof; on the other I’d hate to destroy my punch, the are hard to find :-)

        Thanks for the feedback. I too have 3 rolls of the original stuff on the shelf, thought it’s discolored over time so the edges might be browner than the center.

        I will probably see how much a custom run will cost.

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