calculator

132 Articles

Solve: An ESP32-Based Equation Solving Calculator

October 15, 2024 by 10 Comments

We’re suckers for good-looking old-school calculators, so this interesting numerical equation-solving calculator by [Peter Balch] caught our attention. Based around the ESP32-WROOM-32 module and an LCD, the build is quite straightforward from an electronics point of view, with the main work being on the software side of things.

A custom keyboard was constructed on Veroboard using a handful of tactile switches arranged in a charlieplexing array to minimize the number of IO pins consumed. For the display, an off-the-shelf 240×320 ILI9341-based module hooked up by SPI was used. A single lithium cell was used for the power supply, connected to a USB

You don’t need much to make a usable keyboard.

charger module, but you could just as easily substitute a 3 x AA battery box. The case was designed in DesignSpark mechanical and 3D printed. It’s unclear what keyboard version they settled on; there are options for one with keycaps and one without. Regardless, a 3D-printed frame sits atop the keyboard circuit, with the graphics printed on photo paper and a protective coversheet on top. Continue reading “Solve: An ESP32-Based Equation Solving Calculator” →

A black OLED screen with a happy face displayed upon it is situated at the top of a squarish calculator with a 5x6 grid of white calculator keys. It floats above a graphing calculator, Nintendo Switch, aigo numpad, and an Arduino Mega on a white table. A handful of differently-colored kalih choc switches are in various places around the table.

Mechanical Switch Sci-Calc Is Also A Macropad

October 4, 2024 by 6 Comments

Smartphones have replaced a desktop calculator for most folks these days, but sometimes that tactility is just what you need to get the mathematical juices flowing. Why not spruce up the scientific calculator of yore with the wonders of modern microcontrollers?

While you won’t be able to use Sci-Calc on a standardized test, this classy calculator will let you do some pretty cool things while clacking on its mechanical choc switches. Is it a calculator? Obviously. Is it an Arduboy-compatible device that can play simple games like your TI-84? Yes. Is it also a macropad and ESP32 dev board? Why not? If that isn’t enough, it’s also takes both standard and RPN inputs.

[Shao Duan] has really made this device clean and the menu system that rewrites main.bin based on the program selection is very clever. Escape writes main.bin back into the ROM from the SD card so you can select another application. A few classic games have already been ported, and the process looks fairly straightforward for any of your own favorites.

If you’re hankering for more mathy inputs, checkout the Mathboard or the MCM/70 from 1974.

Continue reading “Mechanical Switch Sci-Calc Is Also A Macropad” →

Internet Connected TI-84 To Cut Your Academic Career Short

September 29, 2024 by 22 Comments

In an educational project with ethically questionable applications, [ChromaLock] has converted the ubiquitous TI-84 calculator into the ultimate cheating device.

The foundation of this hack lies in the TI-84’s link protocol, which has been a mainstay in calculator mods for years. [ChromaLock] uses this interface to connect to a tiny WiFi-enabled XIAO ESP32-C3 module hidden in the calculator. It’s mounted on a custom PCB with a simple MOSFET-based level shifting circuit, and slots neatly into a space on the calculator rear cover. The connecting wires are soldered directly to the pads of the 2.5 mm jack, and to the battery connections for power.

But what does this mod do? It connects your calculator to the internet and gives you a launcher with several applets. These allow you to view images badly pixelated images on the TI-84’s screen, text-chat with an accomplice, install more apps or notes, or hit up ChatGPT for some potentially hallucinated answers. Inputting long sections of text on the calculator’s keypad is a time-consuming process, so [ChromaLock] teased a camera integration, which will probably make use of newer LLMs image input capabilities. The ESP32 doesn’t handle all the heavy lifting, and needs to connect to an external server for more complex interfaces.

To prevent pre-installed programs from being used for cheating on TI-84s, examiners will often wipe the memory or put it into test mode. This mod can circumvent both. Pre-installed programs are not required on the calculator to interface with the hardware module, and installing the launcher is done by sending two variables containing a password and download command to the ESP32 module. The response from the module will also automatically break the calculator out of test mode.

We cannot help but admire [ChromaLock]’s ingenuity and polished implementation, and hopefully our readers are more interested in technical details than academic self-sabotage. For those who need even more capability in their calculator, we’d suggest checking out the NumWorks. Continue reading “Internet Connected TI-84 To Cut Your Academic Career Short” →

Reverse Time Back To The Days Of RPN

September 26, 2024 by 68 Comments

While Texas Instruments maintains dominance in the calculator market (especially graphing calculators), there was a time when this wasn’t the case. HP famously built the first portable scientific calculator, the HP-35, although its reverse-Polish notation (RPN) might be a bit of a head-scratcher to those of us who came up in the TI world of the last three or four decades. Part of the reason TI is so dominant now is because they were the first to popularize infix notation, making the math on the calculator look much more like the math written on the page, especially when compared to the RPN used by HP calculators. But if you want to step into a time machine and see what that world was like without having to find a working HP-35, take a look at [Jeroen]’s DIY RPN calculator.

Since the calculator is going to be RPN-based, it needs to have a classic feel. For that, mechanical keyboard keys are used for the calculator buttons with a custom case to hold it all together. It uses two rows of seven-segment displays to show the current operation and the results. Programming the Arduino Nano to work as an RPN calculator involved a few tricks, though. [Jeroen] wanted a backspace button, but this disrupts the way that the Arduino handles the input and shows it on the display but it turns out there’s an Arudino library which solves some of these common problems with RPN builds like this.

One of the main reasons that RPN exists at all is that it is much easier for the processor in the calculator to understand the operations, even if it makes it a little bit harder for the human. This is because early calculators made much more overt use of a stack for performing operations in a similar way to Assembly language. Rather than learning Assembly, an RPN build like this can be a great introduction to this concept. If you want to get into the weeds of Assembly programming this is a great place to go to get started.

Slim Tactile Switches Save Classic TI Calculator With A Bad Keypad

September 10, 2024 by 16 Comments

For vintage calculator fans, nothing strikes more fear than knowing that someday their precious and irreplaceable daily driver will become a museum piece to be looked at and admired — but never touched again. More often than not, the failure mode will be the keypad.

In an effort to recover from the inevitable, at least for 70s vintage TI calculators, [George] has come up with these nice replacement keypad PCBs. The original membrane switches on these calculators have a limited life, but luckily there are ultra-slim SMD tactile switches these days make a dandy substitute. [George] specifies a 0.8 mm thick switch that when mounted on a 1.6 mm thick PCB comes in just a hair over the original keypad’s 2.2 mm thickness. He has layouts for a TI-45, which should also fit a TI-30, and one for the larger keypads on TI-58s and TI-59s.

While these particular calculators might not in your collection, [George]’s goal is to create an open source collection of replacement keypads for all the vintage calculators sitting in desk drawers out there. And not just keypads, but battery packs, too.

Retro Calculator Panders To Trekkies… Or Trekkers

July 19, 2024 by 9 Comments

Back in 1976, when calculators were not common or cheap, a company named MEGO made the Star Trekulator: a calculator sporting a Star Trek theme. However, it was a bit odd since the calculator didn’t correspond to anything you ever saw on the TV show. It was essentially a very simple calculator with a Star Trek picture and some blinking LEDs. [Computer History Archives Project] has two examples of the rare calculator and shows them off, including the insides, in the video below. We’ve also included a vintage commercial for the device a little farther down.

Inside the 5-inch by 9.5-inch cabinet was an unremarkable printed circuit board. The main component was a TI calculator chip, but there were a surprising amount of other components, including three that [Computer History Archives Project] could not identify.

MEGO was known for making Star Trek toys, including a cassette player that (sorta) looked like a tricorder and communicator walkie-talkies. We wish they’d made the calculator look like some sort of prop from the show, although the beeping noises, we suppose, were supposed to sound like the Star Trek computers.

Honestly, we want to 3D print a case to replicate this with modern insides that can drive a display to put different Trek clips and sound effects out. Now, that would be something. Maybe [Michael Gardi] can take a look at it when he’s got a spare minute. If anything, the calculator looks too advanced to be on the original series. They should have gone VFD. Although Mr. Spock has been seen with a flight slide rule (an E6-B, if we recall). We prefer our props to look like the real ones, thank you.

Continue reading “Retro Calculator Panders To Trekkies… Or Trekkers” →

Early “Computer Kit” Really Just A Fancy Calculator

June 16, 2024 by 22 Comments

We’re big fans of calculators, computers and vintage magazines, so when we see something at the intersection of all three we always take a look. Back in 1966, Electronics Illustrated included instructions in their November issue on building, in their words, a “Space-Age Decimal Computer!” using neon lamps, a couple of tubes, and lots of soldering. The article starts on page 39 and it’s made fairly clear that it will be an expensive and complicated project, but you will be paid back many times over by the use and experience you will get!

Our modern idea of a computer differs greatly from the definitions used in the past. As many readers likely know, “Computer” was actually a job title for a long time. The job of a computer was to sit with pen, paper, and later on electromechanical devices, and compute and tabulate long lists of numbers. Imagine doing payroll for large companies completely by hand, every month. The opportunity for errors was large and was just part of doing business. As analog and later transistor-based computers started to be developed, they replaced the jobs of human computers in calculating and tabulating numbers. This is why IBM was originally called the Computing, Recording and Tabulating Company!

Continue reading “Early “Computer Kit” Really Just A Fancy Calculator” →