Do you need a calculator? Do you like soldering? If you answered “yes” to both of these questions, then YouTuber Volos Projects has just the project for you!
His DIY calculator features a 4x4 matrix of buttons, with a 17th button to the upper-right of this array — allowing for the numerical input, as well as the plus, minus, multiply, and divide functions that you’d expect from a simple calculator.
Each button is wired to its own DIO pin, along with three buttons wired to a trio of analog pins acting as digital inputs. All of this soldering and wire work gets a bit messy, but he was able to form a nice enclosure for the calculator using a set of standoffs and a second perfboard on the bottom.
Besides being a fun (?) exercise to develop your soldering skills, it could also be a good intro into how to create an Arduino-style microcontroller setup using an ATmega328P chip and other components. The build also shows off another trick that is certainly obvious to some, but will be new to others, as Volo programs the microcontroller in an actual Arduino Uno, then pops out the chip to fit into his new calculator assembly.
The video below goes through the entire process, which could be really good if you want to follow along at home. Code for the calc is available here.