The Clue Coffee Scale
Achieving the perfect cup of coffee relies on precision, and controlling the brew ratio is a key part of that process. The Clue Coffee Scale, designed for espresso enthusiasts, offers an easy way to precisely measure both coffee grounds and the espresso extraction itself.
This DIY project is mounted directly on the espresso machine’s drip tray and uses a load cell sensor, an analog-to-digital converter (ADC), and Adafruit’s Clue microcontroller running CircuitPython to display real-time weight measurements. With its responsive interface, including a visual scale on an OLED screen and customizable software, it ensures consistency in your espresso shots every time.
The scale uses a load cell attached with aluminum brackets and measures changes in resistance using the NAU7802 24-bit ADC breakout board. It sends this data to the Clue board, where a Python script processes the results and displays weight in both grams and ounces. The Clue board’s flexibility allows for easy customization through CircuitPython, making it possible to fine-tune the display or add new features.
Project Steps Overview:
- Assemble the Scale: Attach the load cell, plates, and screws to the espresso machine’s drip tray. Properly mount it to allow flexing for accurate weight readings.
- Wiring and Electronics: Wire up the load cell to the ADC board and Clue microcontroller using heat-shrink tubing and wire ferrules for clean, solid connections.
- Software Installation: Install CircuitPython on the Clue board and upload the necessary project files, including code for calibration and display graphics.
- Calibration: Before use, calibrate the load cell by measuring a known weight and adjusting the calibration ratio in the software to ensure accurate measurements.
- Customization: You can easily modify the software to update display settings or add additional features such as different measurement units or timing capabilities for shot extraction.
Once built, the Clue Coffee Scale makes pulling a consistent espresso shot straightforward. For example, you can easily aim for a 1:1.5 brew ratio by weighing 20g of coffee grounds and pulling a 30g shot over 30 seconds, then refining based on taste by adjusting grind or extraction time.
The scale also features a tare button for easy weight adjustments, ensuring that containers or cups are excluded from the final measurements. The responsive display will alert you if the weight exceeds the intended range with a color change, offering a dynamic and reliable brewing assistant.
This precision tool elevates the art of making espresso, making it easier to refine recipes and replicate your perfect shot time after time!
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