extrakt_silvia

Extrakt – Open-Source Espresso Machine Controller

Extrakt is an open-source hardware controller designed to modernize classic espresso machines with precise control, monitoring, and extensibility, while keeping the system robust, serviceable, and understandable.

The project targets machines with AC pumps, heaters, and solenoid valves (e.g. Silvia-class designs) and focuses on reliability, electrical safety, and clean power/analog design, rather than “IoT for the sake of IoT”.

Key Features

• STM32G431 main controller for real-time control and safety-critical logic

• ESP32-WROOM-32E companion MCU for connectivity and UI integration

• Triac-based AC control for pump, heater, and 3-way valve using zero-cross optotriacs

• Isolated AC/DC power supply (230 VAC → 5 V) with full EMI and surge protection

• High-efficiency DC/DC (5 V → 3.3 V) for digital and analog domains

• Separated VDDA and VDD rails with ferrite-bead filtering for low-noise ADC operation

• Load-cell support via NAU7802SGI for integrated drip-tray or brew-by-weight scales

• Pressure sensing (analog) for brew pressure monitoring

• K-type thermocouple support for temperature measurement

• CAN bus between STM32 and ESP32, enabling robust communication and firmware updates

• Designed for Katapult-style firmware updates via the ESP32

Electrical Design Highlights

• Complete mains EMI input filter (fuse, MOV, common-mode choke, X2 capacitor)

• RC snubbers and gate conditioning for reliable triac switching of inductive loads

• TVS protection on low-voltage rails

• Careful grounding strategy for mixed-signal design (digital + analog)

• Appliance-grade component selection with attention to creepage and clearance

Design Goals

• Deterministic, real-time control on the STM32

• Noise-resilient analog measurements

• Safe operation in a high-EMI, high-voltage environment

• Modular firmware and hardware architecture

• Repairability and hackability over black-box solutions

Project Status

• Hardware: schematic design in progress

• Firmware: early development / planning stage

• This repository currently focuses on hardware design (schematics, power, and triac stages)

License

This project is open hardware.
Schematics and PCB designs are released under an open-source hardware–compatible license.
Firmware will be released under an open-source software license.