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The Clue Coffee Scale is an Adafruit do-it-yourself project, not a finished scale you can buy and use out of the box. It combines an Adafruit CLUE development board, a strain-gauge load cell and a NAU7802 analog-to-digital converter (ADC) to display coffee weight—especially espresso input or output—on a machine-specific mount.
It can be a rewarding build for someone comfortable with electronics, coding and fabrication. If you want a ready-to-use, protected, predictable coffee scale, a commercial model is the simpler choice. The project is an educational reference, not a certified measuring instrument.
What is the Clue Coffee Scale?
Adafruit’s project, by Jan Goolsbey and John Park, was first published on August 17, 2022; the guide lists an update on February 24, 2025. Its central idea is to integrate a small weight display into an espresso machine’s drip-tray area. The CLUE supplies the display, buttons and microcontroller; it does not contain the weighing sensor.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchThe documented system uses an Adafruit CLUE nRF52840 Express, a four-wire, 1-kilogram strain-gauge load cell and an Adafruit NAU7802 24-bit ADC breakout. CircuitPython code reads the ADC and presents the result. The exact bracket and installation are not universal: the guide’s mechanical arrangement is one implementation, and another machine may require different plates, clearances and mounting points. See Adafruit’s project overview.
#1 Best Overall
- 【Ultra Small, Yet Professional】The Espresso Scale is small enough to fit in your palm. It measures 4.13*4.13*0.78 inches and weighs just 0.75 pounds. The coffee scale can work on most espresso machines and small pour-over coffee stands. It's easy to store and carry around, making it perfect for coffee lovers who like outdoor coffee.
- 【0.1g High Precision】This digital kitchen coffee scale is equipped with high-precision sensors and a reliable microprocessor, guaranteeing precise measurements every time. With an accuracy of 0.1g and a range of 0.5g-2000g, it is particularly well-suited for espresso and pour-over brewing methods, ensuring impeccable results.
- 【Three Units & Dual Timekeeping Modes】The Espresso Digital Timer Scale has three units of measurement (g/oz/ml) that can be converted at any time. The small coffee scale has two built-in timing modes, automatic and manual, allowing you to accurately time the coffee brewing process. This feature ensures that your coffee is always delicious and perfectly brewed to your taste.
- 【Long Standby Rechargeable Battery 】The gram scale has a built-in 500 mAh lithium battery and a USB-C charging cable in the package. There is no need to replace or buy batteries; they can be used for up to 90 days on a single charge. The coffee scale will automatically enter sleep mode after 5 minutes of inactivity to save power.
- 【Elegant Design & Premium Materials】Maestri House Digital Coffee Scale features a sleek, minimalist design with borosilicate glass surface. It adds elegance to your kitchen, seamlessly blending with your decor. With a hidden LED display and touch-sensitive controls, its seamless surface enhances aesthetics and ensures waterproof, easy cleaning. It includes a detachable silicone pad for surface protection, offering waterproof, slip-resistant, scratch-resistant, and heat-insulating properties.
What it measures—and what that helps you do
Used with a stable platform, the scale measures mass. That can help you weigh a coffee dose before brewing or the espresso collected in a cup. Comparing dose and output lets you repeat or adjust a brew ratio. The scale does not make coffee better automatically; it makes quantities measurable so you can make changes deliberately.
The project does not document automatic brew profiling, flow-rate measurement, an app, or Bluetooth logging. The CLUE board has Bluetooth Low Energy, but that capability alone does not mean this project includes a phone workflow.
How the measurement chain works
A load cell bends slightly under force. Strain gauges bonded to its metal body change resistance as it flexes, producing a very small differential electrical signal. The NAU7802 amplifies and digitizes that signal; the CLUE runs the software that applies calibration and displays a weight reading.
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This is why a load cell by itself is not a complete scale. The ADC, wiring, mechanical load path, calibration and software all matter. Nor does a “24-bit” ADC specification guarantee 24-bit real-world accuracy: noise, mounting, temperature, vibration and the sensor’s own behavior affect the result.
Rank #2
- Compact and Mini Design: This coffee scale is mini in size, measuring 4.11x4.11x0.79 inches. It can be placed directly in the palm of your hand and can be easily placed on the coffee machine's water tray, leaving enough space to hold coffee cups. It is suitable for home coffee machines or small travel coffee machines.
- Precise Measurement: This kitchen espresso scale is equipped with a high-precision sensor, with a weighing range of 0.3 to 2000g and an accuracy of 0.1g, This ensures that even the slightest differences in coffee grounds and extracts can be accurately captured, thereby stabilizing the coffee flavor.
- LED Display Screen: The coffee scale with timer is made of a smooth glass platform and a hidden LED screen, which can be clearly read even in backlit or low-light environments, making it suitable for outdoor coffee lovers. The espresso scale also comes with a silicone pad to prevent water or heat, making coffee brewing safer.
- Three Modes: Manual, automatic, and water flow speed modes. You can switch modes by simply touching "TARE" according to your needs.
- Ingenious Design: You can long press the "TARE" and "TIMER" buttons to turn on or off the beeping sound, thereby switching to silent mode and enjoying a wonderful coffee brewing process.
What the documented interface does
The guide describes a display with readings in grams and ounces, a central five-division graduated scale and a bubble marking the current reading. The default full-scale display range is 100 grams. If a reading falls outside the displayed range, the bubble turns red; that is a display-range warning, not permission to exceed the load cell’s rating.
To tare, place the empty cup, portafilter or other vessel on the platform, then press and hold the CLUE A button and release after the first beep. The indicator bubble and CLUE NeoPixel turn red during the operation; a second beep signals completion. Keep the platform and its load still throughout, since motion or vibration can set an incorrect zero. Details are in Adafruit’s features and operation guide.
Parts and machine fit
The official parts list includes:
- Adafruit CLUE nRF52840 Express with Bluetooth LE and its clear acrylic enclosure kit
- A four-wire, 1-kilogram strain-gauge load cell
- Adafruit NAU7802 24-bit ADC breakout
- A STEMMA QT JST-SH four-pin cable
- A three-AAA battery holder with switch and a USB cable
- Adhesive squares, an aluminum extrusion corner brace, a coupling plate, a cross-plate and wire ferrules
These are the guide’s listed components, not a guarantee that every part will remain available or suit every machine. Before sourcing hardware, inspect the drip tray and measure its usable area, the vertical clearance under the cup, and where the display and battery can sit. Decide whether the platform must take a cup, portafilter or both. Account for heat, steam, spills and battery access. A different machine may need another bracket, platform, hole pattern or protective enclosure.
Mechanical mounting: clearance is part of the scale
In the documented assembly, the load cell’s wired end is its fixed end, secured with M5 hardware. The flexible weighing end uses M4 hardware; an M4 screw attaches the large cross-plate beneath it, while an M5 screw attaches the three-hole coupling plate to the fixed end. M3 hardware mounts the assembly to the drip-tray grid, with spacers leaving room for the cell to flex. Follow the load cell’s marked orientation and load direction rather than improvising them.
Rank #3
- Barista-Level Precision: A 0.1g high-precision sensor with a rapid refresh rate responds instantly to changes in weight, helping you achieve consistent results across espresso, pour over, drip coffee, Chemex, V60, and filter coffee brewing.
- Integrated Brew Timer: A built-in count-up and count-down timer tracks bloom, extraction, and espresso shots. Ideal for dialing in espresso, timing Chemex and V60 pour over recipes, or steeping tea. Auto-shutoff helps preserve battery life between brews.
- Durable Waterproof Silicone Cover: The heat-resistant, dishwasher-safe silicone cover helps protect the coffee scale's spacious 5.25" x 5.25" weighing surface from splashes, spills, and hot equipment. The grooved surface provides added stability and makes cleanup quick and easy.
- Versatile Measurement Options: Quick-tare and 6 unit options make it easy to weigh coffee beans, espresso shots, matcha portions, and more. Choose from g, ml, lb, lb:oz, oz, and fl oz for added flexibility in the kitchen and coffee bar.
- Intuitive Design: A bright dual-color LCD display clearly separates weight and timer readings, while simple controls make daily brewing easy. Includes 3 AAA batteries and is backed by 5 years of coverage, with support from our St. Louis-based team whenever you need a hand.
The platform must bear weight through the load cell without rubbing on the frame, drip tray or espresso machine. Such contact can divert force, distort readings or overload the sensor. Keep the load centered as much as practical and make sure the assembly stays stable when brewing. The guide uses an aluminum corner brace to position the CLUE at the tray front and attaches the battery holder so it can be removed for replacement. Its build guide shows the specific arrangement; treat it as a reference, not a universal fit.
Wiring, software and settings
The load cell’s fine wires connect to the NAU7802 screw terminals, and a STEMMA QT cable connects the ADC to the CLUE. Wire colors are not universal. Use the documentation for your specific sensor or identify the wire pairs; do not rely on a generic color chart. The guide suggests short heat-shrink sections and ferrules to organize and secure the delicate wires.
The CLUE runs CircuitPython and the project imports the cedargrove_nau7802 library. Follow the current instructions for CircuitPython on CLUE and the guide’s code setup rather than relying on old firmware or file names. The code guide identifies these settings:
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MAX_GR = 100
DEFAULT_GAIN = 128
SAMPLE_AVG = 5
SCALE_NAME_1 = "COFFEE"
SCALE_NAME_2 = "SCALE"MAX_GRsets the display’s full-scale range in grams. The guide suggests values such as 1000, 500, 250, 100, 50, 25, 10 or 5, since the visual scale is divided into tenths. Choose a display range for the task; it does not change the load cell’s physical rating.DEFAULT_GAINsets the NAU7802 programmable gain; the documented default is 128.SAMPLE_AVGsets how many measurements are averaged. More averaging generally steadies the display but slows its response; less averaging can make it faster and noisier.- The two display-name strings are limited to six characters each; uppercase is recommended for readability.
See Adafruit’s code details for context on these settings.
Rank #4
- PRECISE MEASUREMENT & WIDE RANGE: KitchenTour EK6002 defines the latest in precision weighing technology with a weight capacity from 0.3g - 3000g to help you measure and get an exceptional cup of coffee with refined accuracy
- MULTI-FUNCTIONAL COFFEE & FOOD SCALE: The electronic coffee scale has a built-in timer to cook and time your coffee to ensure the consistency of each cup of coffee. With Tare Function, You can add different ingredients or coffee powder and water in the same container to make your cooking more accurate and simple. It also features 120s Auto-off and Low battery reminder function
- SUPERIOR QUALITY MATERIAL: This Kitchen Drip Coffee Scale is crafted to be sturdy, accurate, safe, and user-friendly. Constructed with a high-quality ABS platform and frame, this digital kitchen scale is durable and easy to clean and maintenance. A waterproof Silicone Non-Slip pad included
- UNIT CONVERSION: KitchenTour High Precision Coffee Drip Scale supports switching of different units of g, oz, ml, which can weigh solids, liquids, powders. The touch activated keys also make for an elegant and clean design. With the back-lit reverse LCD display, weighing is quick and easy
- VERSATILE USE FOR KITCHEN WHILE COOKING & DRINKING: Excellent for cafe and home use, enabling you to weigh your coffee and water down to a tenth of a gram. With a built-in timer, you won't have to break your attention from your coffee brewing area
Calibrate after the mechanics are installed
Calibration is specific to the load cell and its installed geometry. A ratio converts the sensor’s raw reading to grams. The project gives this example using a 100-gram reference mass and a raw reading of 215,300:
CALIB_RATIO = 100 / 215300That number is an example, not a reusable setting for every build. Install the platform first, use a known reference mass, run the project’s calibration procedure, record the raw reading and calculate or enter the ratio as the guide directs. Then check more than one known weight and repeat the test. Adafruit also notes that a U.S. dime weighs 2.268 grams (0.079 ounces), but a small coin is not an ideal reference when dependable calibration matters. Follow the calibration guide.
Recalibrate if you replace the load cell, change the mounting or platform, move the assembly, alter the ADC gain, introduce friction or persistent contact, or get implausible readings. Tare before a brew, but do not mistake repeated taring for calibration: tare resets the current zero; calibration sets the conversion from sensor signal to weight.
Troubleshooting by symptom
- No reading or implausible values: Check the CLUE-to-ADC cable, load-cell terminal connections and the sensor’s documented wire pairs. Verify that the cell is oriented and loaded in its intended direction. Recheck code setup and calibration.
- Unsteady readings: Look for loose fasteners, a platform touching the frame or tray, vibration, poor wire connections or a tare performed while something was moving. Confirm the load cell can flex freely. Raising
SAMPLE_AVGmay steady the display, at the cost of response speed. - Response feels slow: Reduce
SAMPLE_AVGto shorten averaging, then judge whether the added fluctuation is acceptable. - Tare is wrong: Remove movement and contact from the platform, place the empty vessel on it, and tare again. If zero continues to drift, inspect mounting stress and clearance and check whether the mechanical setup has changed.
- Indicator turns red: The reading is outside the displayed
MAX_GRrange. You can change that range in code, but never exceed the load cell’s rating or assume the entire assembly can safely take its nominal sensor load. - Readings vary with cup position: Center the load and check the platform for rubbing or uneven support. Off-center loading can expose limitations in the mechanical arrangement; test repeatability at the positions you actually use.
These are practical engineering checks, not claims of independently tested performance. Persistent zero drift or poor repeatability may require revisiting the mounting and calibration rather than changing a display setting.
Best Value
- Important: Please remove the 4 plugs from under the weighing platform before use
- Accurate and Responsive: With the latest weighing technology and high-precision sensor, this electronic kitchen scale can stabilize faster during brewing and respond sensitively to every 0.1g increase. Provide you with accurate measurement from 0.3g to 3000g
- Premium Materials: Being sturdy, safe and easy to clean and maintain. The platform is made of premium ABS material, which is durable and heat-resistant. Equipped with a removable silicone pad to protect the surface, which is waterproof, non-slip, scratch-resistant and heat-insulating
- Professional-grade Coffee Scale: Features automatic timing to help you follow brew recipes exactly and ensure consistency. Supports precise tare function and 6 measurement units: g, ml, oz, lb, lb:oz, fl'oz, perfect for espresso and pour over coffee as well as kitchen use
- USB Type-C Charging: Built-in 600mAh rechargeable lithium battery. More environmentally friendly and safe, can be fully charged in 3 hours and last for 30 days - use once a day, 10 minutes/time
Accuracy, environment and intended use
Keep separate the display’s smallest step, repeatability, accuracy, response time and maximum load. A fine-looking display or high-resolution ADC does not establish that a finished build measures accurately. The guide does not provide independent accuracy testing for every possible assembly, and the result depends on the particular sensor, installation, wiring, calibration and operating conditions.
Adafruit warns that component variation and software limitations mean the project should not be used for safety, health, scientific or commercial weight measurement. It is a hobby coffee-scale project, not a trade-certified or laboratory instrument. The guide also does not establish a waterproof, splash-proof or heat-resistant rating. Keep the CLUE, ADC, battery, connectors and wiring away from direct liquid, steam and excessive heat; add suitable physical protection without obstructing the load cell’s movement.
Build it or buy a commercial scale?
Build this project if you already use or want a CLUE, enjoy electronics and fabrication, and value a custom integrated display more than convenience. It offers room to learn about load cells, ADCs, CircuitPython and calibration, and to alter the display range, labels and averaging.
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Buy a ready-made scale if you need something that works immediately, a protected body, warranty-backed support or features such as a timer, automatic operation or app logging. Those features are not documented for this project. Compare any commercial option on size, capacity, response, protection from water and heat, battery life, support and availability in your region; no particular current model or price is established here.
The DIY bill of materials also does not settle whether the project is cheaper: parts, shipping, fabrication materials and substitutions vary, and stock changes. The official parts list is a component-shopping reference, not a finished-product listing.
Who should build it?
This is best for makers who want a machine-specific electronics project and are prepared to troubleshoot, calibrate and protect it. It is a poor fit for someone seeking a plug-and-play appliance, certified measurement, an app-connected workflow, or a universal bracket. Its appeal is customization and learning—not a promise of commercial-scale convenience or accuracy.
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