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Retro computing enthusiast creates perforated tape reader designed 'from scratch' — reads data at about 50 bytes per second
A retro computing aficionado, electronics enthusiast, and maker has demonstrated a freshly created perforated tape reader, dubbed the Putapre. Skyriver says they designed this highly compact device from scratch (machine translation) using minimal parts. The maker’s device is said to be much faster than punched tapes or cards of old which used contact-based sensing technology, as this device uses an optical sensor and modern microcontroller to read the data. We roughly estimate the data transfer speed at approximately 50 bytes per second, but expect the device could perform faster over a longer data feed.
Click ‘See more’ to watch the perforated tape demo video
Skyriver explains that they were inspired to create this reader from their retro-tech-stuffed social media feeds. Perforated tapes and punch cards are deeply rooted in the history of computing and were used to store and recall machine data even before the era of computing. So, it is easy to understand the lure of such a project. Moreover, images of these tapes certainly have a visual appeal.
A single, simple USB-enabled 8‑bit microcontroller from Microchip’s PIC18 family was used as the brain behind the project. As for other major components, we’d highlight the phototransistor and infrared LED behind the ‘mechanics’ of the reader, providing light to shine through perforations and a way to check where holes are situated.
Skyriver’s blog delves into the technical details of adjusting LED strength and sensor configuration. They kindly share some of the testing results and sweet spot specifications, which they say “took a lot of time to adjust.” Other adjustments required to make the system work well involved measures against crosstalk, and even the choice of paper tape material. Finally, a 3D printed tape guide and some practice got things working well on the hardware side.
The maker doesn’t talk much about the software, but you can see it does the job in the demo video. Nevertheless, Skyriver indicates this is an area for attention, to add polish to the project.
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The punched card computer era ended in 1984, when IBM discontinued such systems, but was largely superseded by magnetic tape starting from the 1950s.
On the topic of ‘what’s next,’ Skyriver says they hope to make a matching compact device to create punched tapes for this system. Currently, the enthusiast has to create vector files (apparently DXF) and output them using a laser cutter and engraver. That sounds like a laborious way to create the tapes. Though this project is hardly about efficiency… It is for fun, of course.
Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.
Let's see, what would be the 21st-century answer to punching holes in bristol paper?
How about...a holographic lens on a 5-watt laser that burns a perfect circle each time you switch on the beam? Eight of those, side by side. With the laser fume collector adapted to slurp the chads out.
The maker’s device is said to be much faster than punched tapes or cards of old which used contact-based sensing technology, as this device uses an optical sensor and modern microcontroller to read the data.
Optical reading of punched tape is about as old as punched tape. e.g. the Bendix G-15 is a mid-50's computer with a built-in 200 char/s photoelectric reader (lamp source with Germanium diode photosensors) and an optional 400 char/s external photoelectric reader. The G-15 used 5-bit characters, so that's a 1kb/s and 2kb/s reader respectively. If we assume this modern reader's "50 bytes per second" is with 8-bit bytes, that's 400bit/s, so still less than half the speed of the old Bendix's basic optical; punched tape reader.
I'm sure somebody was hooking up old contactor readers to digital computers (possibly as a retrofit to an older system for backward compatibility with an old datastore), but punch card/tape operation not using photoelectric reading was a pre-electronic system.
Reading is dead simple. I've done it myself back in the earliest homebrew days and sent the data in parallel to my 8080 PC using an interrupt handler. Get back to me when there is a tape punch to go along with it.
