# Walnut Case Sets This Custom Arduino-Powered RPN Calculator Apart From The Crowd

How many of us have an everyday tool that’s truly unique? Likely not many of us; take a look around your desk and turn out your pockets, but more often than not, what you’ll find is that everything you have is something that pretty much everyone else on the planet could have bought too. But not so if you’ve got this beautiful custom RPN calculator in a wooden case.

This one comes to us from [Shinsaku Hiura], who generally dazzles us with unique mechanical clocks and displays. This calculator solves a more practical problem — the dearth of RPN calculators on the market with the correct keyboard feel, specifically with the large keys and light touch he desired. Appropriately, the build started with a numeric keypad, which once liberated of its USB interface was reverse-engineered to figure out how the matrix was wired. Next up, a custom PCB to connect the keypad to an Arduino and a 20×4 LCD display was milled up, while a test case was designed and printed to check fitment. The final case was milled from a block of solid walnut and fitted with an acrylic window, for a sharp look with clean lines and pleasing colors.

As for the calculator itself, the demo below shows it going through its paces. The code is clever because it leverages the minimal number of keys available by hiding all the scientific and engineering functions behind a “secret silver key” that was once the equals key and obviously not needed in RPN. Hats off to [Shinsaku] for a handsome and unique addition to his desk.

## 12 thoughts on “Walnut Case Sets This Custom Arduino-Powered RPN Calculator Apart From The Crowd”

1. Ale says:

It is a very nice case, and full size keys, remembers me of the Czerweny calculators.

2. Teslaspecter says:

Whats an rpn?

1. Gregory S Key says:

RPN stands for Reverse Polish Notation, a method of data entry more efficient than most algebraic based calculators. Google it.

2. rclark says:

RPN – Reverse Polish Notation. Easy way to calculate. Just to a search for the history. Most all of us older Computer Science majors and Engineers used them from the 70s to present. HP was ‘the’ last word on RPN calculators at the time. I still use my HP 15C and 16C and the house calculator is currently a 12C.

Nice job on the calcular! Unique.

1. rclark says:

That’s calculator .zzz. Wish one could edit posts.

3. Truth says:

you give the device the numbers and then the operation you want executed.
so 4/2 would be entered as:
4
2
/
2

1. The Commenter Formerly Known As Ren says:

Well, actually,
4
[Enter]
2
/
Withe the result (quotient? )
2
Displayed
(Sorry to nitpick, really!)

1. I am left-handed and am really fed up with the right-handed world…

1. The Commenter Formerly Known As Ren says:

Open source allows you to build one with a 3° tilt in the other direction.
Or is it a 177° tilt?

3. RunnerPack says:

The face could use a chamfer all around, and some tung oil or other finish, but otherwise very nice.

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