MaraX Evolution - Scale

This repository contains the hardware design, 3D printed parts, and mounting instructions for the MaraX Evolution Scale. This is an optional but highly recommended add-on for the MaraX Evolution Main Controller.

By integrating a load cell directly into the drip tray, the machine gains real-time gravimetric data, enabling Flow Profiling (controlling pump pressure based on flow rate and/or weight).

Features

• Invisible Integration: Designed to fit seamlessly under the drip tray of the Lelit Mara X.

• High Precision: Uses a load cell coupled with an ADS1232 24-bit ADC for ultra-precise readings with an LT6658 for excellent voltage stability.

• Advanced Filtering: The system implements Dual Kalman Filters (running on the main controller):

  • Weight Filter: Smooths raw load cell data for stable readings.

  • Flow Filter: Derives a stable flow rate (g/s) from weight changes, essential for flow profiling.

• Smart Taring: Auto-tare functionality integrated into the machine's state machine (tares on startup/idle).

• Calibration Wizard: Built-in firmware wizard to calibrate using known test weights via Telnet, MQTT or the optional HMI device.

Integration with Main Controller

Important: This repository contains hardware only. This scale does not have its own microcontroller. It is a sensor array (Load Cell + ADC) that connects directly to the MaraX Evolution Main Controller.

The logic is handled entirely by the firmware provided in the Controller Repository.

Enabling the Scale

To use this scale, you must uncomment #define HAS_SCALE in the main controller's main.cpp or platformio.ini before flashing the ESP32.

Hardware Overview

The system consists of three main components:

1. Custom drip tray: A custom stainless steel drip tray with mounting holes for an integrated scale and two 750g load cells.

2. PCB: A PCB containing ADS1232 and LT6658 Voltage Reference/Regulator as well as PCF8575 for I2C communication.

3. Cabling: 7 pin wire that connects the controller port with the custom scale PCB.

4. Load cells: 2x 750g load cells that give a current relative to the weight placed on them

User Guide

Parts List

Assembly Instructions

Licensing

This project is dual-licensed to protect the work while allowing for personal study and modification.

• Hardware: The hardware designs, schematics, and 3D models located in this repository are licensed under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.

• Firmware Logic: The code driving this scale is part of the Main Controller project and is subject to its PolyForm Noncommercial License.

Please see the LICENSE file for the full legal text.

Part of the MaraX Evolution Ecosystem.