scientific

2 Articles

An HP15-C emulator PCB

Calculate Like It’s 1989 With This HP15C Emulator

August 31, 2021 by 41 Comments

Back in the day, your choice of calculator said a lot about your chops, and nothing made a stronger statement than the legendary Hewlett-Packard Voyager series of programmable calculators. From the landscape layout to the cryptic keycaps to the Reverse Polish Notation, everything about these calculators spoke to a seriousness of purpose.

Sadly, these calculators are hard to come by at any price these days. So if you covet their unique look and feel, your best bet might be to do like [alxgarza] and build your own Voyager-series emulator. This particular build emulates the HP15C and runs on an ATMega328. Purists may object to the 192×64 LCD matrix display rather than the ten-digit seven-segment display of the original, but we don’t mind the update at all. The PCB that the emulator is built on is just about the right size, and the keyboard is built up from discrete switches that are as satisfyingly clicky as the originals. We also appreciate the use of nothing but through-hole components — it seems suitably retro. The video below shows that the calculator is perfectly usable without a case; a 3D-printed case is available, though, as is an overlay that replicates the keypad of the original.

We’ve seen emulators for other classic calculators of yore, including Sinclair, Texas Instruments, and even other HP lines. But this one has a really nice design that gets us going.

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Reviving A Casio Scientific Calculator, With A CNC Router

April 26, 2019 by 6 Comments

Before Wolfram Alpha, before the Internet, before even PCs, calculations more complex than what could be accomplished with a “four banger” required some kind of programmable calculator. There were many to choose from, if you had the means, and as time passed they became more and more sophisticated. Some even added offline storage so your painstakingly written and tediously entered programs didn’t evaporate when the calculator was turned off.

One such programmable calculator, a Casio PRO fx-1 with magnetic card storage, came across [amen]’s bench recently. Sadly, it didn’t come with any cards, so [amen] reverse engineered the card reader and brought the machine back to its 1970s glory. The oddball mag cards for it are no longer available, so [amen] had to make do with. He found some blank cards of approximately the right size for cheap, but somehow had to replicate the band of vertical stripes adjacent to the magnetic strip on the card. Reasoning that they provide an optical synchronization signal, he decided to use a CNC router to cut a series of fine-pitched slots in the plastic card. It took a little effort to get working, including tapping the optical sensor and reading the signal on an oscilloscope, but as the video below shows, the hacked cards work fine with the vintage calculator.

Kudos to [amen] for reviving this retro-cool calculator. Now that it’s back in action, it might be fun to visualize domains on the magnetic strip. A flatbed scanner can be used for that job.

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