HP-15C Calculator Emulator Designed Around an ATmega Microcontroller

Hewlett Packard’s HP-15C was a high-end scientific calculator released in 1982 to handle complex numbers and matrix operations. The coveted calculator was the cream of the crop until 1989 when it was discontinued, and although they can be found today, they can cost up to $600+ for those in excellent condition. Engineer alxgarza always wanted to own the HP-15C but never had the chance to buy one, so he designed his own using readily available through-hole components.

Alxgarza built an HP-15C calculator emulator around an ATmega328 microcontroller, which provides more than enough power to handle any calculations; in fact, it’s nearly five times faster than the original while running at 8MHz. The keyboard was assembled using discrete switches arranged in the same familiar layout as its 1982 counterpart. He also included an onboard speaker for audible keypress feedback, a 192x64 LCD display (with backlight), a 32.768KHz crystal for a real-time clock, and an onboard CR2032 (3V) battery to power the unit.

While the HP-15C Calculator Emulator isn’t a precise replica of the original, it does come incredibly close. Alxgarza designed a 3D-printed case for the emulator, giving it a streamlined look and compliments the overall aesthetic. Alxgarza has uploaded a complete walkthrough of the build on his project page for those who would like to recreate his replica and start crunching numbers like it's the '80s!