Gravimetric Espresso Mod
A personal project modifying my Rocket Espresso machine into a gravimetric (brew-by-weight) machine — enabling precise measurement and control of espresso extraction for more consistency in every shot.
Features
- Brew-by-weight control: monitors the shot's weight in real time and automatically stops extraction once the target ratio is reached.
- UI: a responsive TFT touchscreen interface showing shot weight, extraction time, and shot settings.
The reference cup was also used for loadcell calibration. The extraction here is 36.64 g — close to the 36 g target (18 g dose at a 1:2 ratio).
Hardware used
- MCU: Nordic nRF52840
- TFT touch: Adafruit 2.8" Capacitive
- SparkFun 500 g loadcell
- NAU7802SGI 24-bit ADC
- TCK108AF load switch IC
Software and tools
- Zephyr RTOS for firmware
- KiCad for PCB design
Current limitations
The E61 group head lever not only activates the pump via a switch, but also mechanically opens the pre-infusion valves. Because of this, the lever must still be operated manually for the controller to work. To make the process fully automatic, the lever would need to be actuated too — by a DC motor, servo, or similar mechanism.
