Gaggia Classic Scale Mod
I took inspiration from the amazing Gaggiuino project, but the only part I really wanted was the scale built into the base of the machine. Ever since I got this machine, the distance between the portafilter and the drip tray annoyed me: there is no room for both a scale and a cup in between. Load cells to the rescue.
I used Gaggiuino's 3D-printable files to build the load cell mount below the drip tray, and connected the load cells to an Arduino Nano via two HX711 amplifier boards.
A rotary encoder changes the target weight of the shot and saves it to EEPROM. Pressing the encoder tares the scale to zero.