Paper Tape Reader Self-calibrates, speaks USB





Input devices consisting of optical readers for punched paper tape have been around since the early days of the computer, so why stop now? [Jürgen]The Paper Tape Reader project connects to any modern computer via USB and works as a serial communication device. Thanks to the machine’s automatic calibration, it works with a variety of paper materials. As for the read speed, it’s pretty much limited only to how fast you can pull the tape through without damaging it.

Stacked 1.6mm PCBs act as a kind of enclosure.

While [Jürgen]The device uses LEDs and phototransistors to detect the presence or absence of perforated holes, it does not rely on hardware calibration. Instead, the device takes analog measurements from each phototransistor and uses software-adjusted thresholds to distinguish ones from zeros. This allows it to easily handle a wide variety of tape types and colors, even working with translucent materials. Reading 500 characters per second is not a problem if the device has had a chance to calibrate.

Interested in making one yourself? The build part of the project contains all the design files; it uses only continuous components and as the unit is constructed from a stack of 1.6mm thick PCBs, no separate housing is required.

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




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