Panel meter calculator with floating point | Hacker News Reader

Panel meter calculator with floating point

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36 pointssurprisetalk9 comments

I didn’t actually know about the Casio 14-A until now. I almost thought the picture was AI-generated. Four functions squeezed into that compact desktop unit in 1957? Impossible with the technology of the time…

The Casio 14-A was indeed the world’s first all-electric desk calculator. But by “desk calculator,” they literally mean “a desk that is a calculator.” The display/keyboard pictured was literally attached to a desk filled with hundreds of relays and weighed 140 kg. [0]

The “all-electric” claim is interesting. There had been scores of electric calculators for decades (Friden, Marchant, etc.) but were merely driven by an electric motor. The calculations were still performed by gears and cams and linkages.

https://www.casioeducation.com/primary-calculators/14-a

I always heard those old mechanical calculators called "adding machines" presumably because addition is all they could do?

For the old mechanical machines (whether powered by a crank or powered by an electric motor) yes, the term "adding machine" was because, for most, all they could do is add:

https://en.wikipedia.org/wiki/Adding_machine

"Subtraction was impossible, except by adding the complement of a number (for instance, subtract 2.50 by adding 9,997.50)."

A few fancier ones could multiply, but they would do so by repeating an addition some number of repetitions. Nearly all output their results on a paper tape much like "store receipts" today, only printed in ink instead of via thermal transfer paper.

You’re not wrong. They work very similar to binary arithmetic: basically the only operations they can do is increment, decrement, and shift left/right (but by 10)

But multiplication is just repeated addition, and division is just repeated subtraction. Some of the highest-end units could do square roots! Check out CuriousMarc’s videos.

Today I learned you can use generic GPIO PWM to fake an analog voltage.

https://ww1.microchip.com/downloads/en/Appnotes/90003250A.pd...

This is also how Arduino emulates analog output, since most micros don’t have a hardware DAC

https://docs.arduino.cc/language-reference/en/functions/anal...

Working in process control, this is an everyday thing for me. But I prefer to use pulse frequency modulation, which is what a lot of dedicated DACs use.

Congrats, you're one of today's lucky 10000! It's extremely common actually. I don't know if they're still doing it but Raspberry Pi 1,2,3 had only PWM audio output, not true analog.

A PWM output followed by an adequate filter can be considered a cheap, low quality type of DAC. You never get the quality as good as you want but you get it good enough.

Awesome project. The video moves a little fast to fully appreciate it, but I did like how it was short & to the point.

It could be fun to implement a scientific notation result display for answers that would otherwise overflow, although off the top of my head I'm not sure what the cleanest way to do that is.

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