# Clue Coffee Scale
## Overview
Consistently brewing that crowning cup of coffee involves attention to the precise addition of ingredients and control of the brew ratio, tempered with practiced technique. Perhaps it's time to apply a little more science to the art.
The Clue Coffee Scale can accurately measure the weight of the ground beans or the extraction output, getting closer to an exact and repeatable approach for creating your preferred brew. To measure the contents of a container, the scale can be zeroed with a push of a button to subtract the container's tare weight.
The scale uses a load cell sensor device that consists of a very sensitive resistance array (a strain gauge) attached to a metal bending beam. When connected to an exciter voltage, the resistance array provides a differential voltage output signal proportional to the torque of the mass placed on the load cell. The signal voltage is very low so a sensitive amplifier and high-resolution analog to digital converter (ADC) are used to provide a microcontroller-compatible measurement.
The [Adafruit NAU7802 24-Bit ADC - STEMMA QT](https://www.adafruit.com/product/4538) board has everything needed to connect a load cell and provide measurements for the Clue. Add a CircuitPython program, and the Clue Coffee Scale is born.
**John Park** built a version of the coffee scale for use with his primo espresso station. Check out the **Build the Coffee Scale** section of this guide for the step-by-step approach he used for his custom scale. A _trenta-sized thank you_ goes to John for creating a practical and beautiful working scale.
This guide will show how to build, calibrate, and code the scale. Your perfect cup of Java awaits.
Warning:
## Parts
Featured
### Adafruit CLUE - nRF52840 Express with Bluetooth® LE
[Adafruit CLUE - nRF52840 Express with Bluetooth® LE](https://www.adafruit.com/product/4500)
Do you feel like you just don't have a CLUE? Well, we can help with that - get a CLUE here at Adafruit by picking up this sensor-packed development board. We wanted to build some projects that have a small screen and a lot of sensors. To make it compatible with existing projects, we made...
In Stock
[Buy Now](https://www.adafruit.com/product/4500)
[Related Guides to the Product](https://learn.adafruit.com/products/4500/guides)
Featured
### Clear Acrylic Enclosure + Hardware Kit for Adafruit CLUE
[Clear Acrylic Enclosure + Hardware Kit for Adafruit CLUE](https://www.adafruit.com/product/4675)
Here is a chic minimalist enclosure for your **CLUE** board! This case has been laser-cut specifically to accommodate the TFT display, tactile buttons, and capacitive pads.
And of course, we include mounting hardware so you can assemble it right onto your CLUE...
In Stock
[Buy Now](https://www.adafruit.com/product/4675)
[Related Guides to the Product](https://learn.adafruit.com/products/4675/guides)
Featured
### Strain Gauge Load Cell - 4 Wires - 1Kg
[Strain Gauge Load Cell - 4 Wires - 1Kg](https://www.adafruit.com/product/4540)
A strain gauge is a type of electronic sensor used to measure force or strain (big surprise there). They are made of an insulating flexible backing with a metallic foil pattern. The resistance of a strain gauge changes when force is applied and the...
Out of Stock
[Buy Now](https://www.adafruit.com/product/4540)
[Related Guides to the Product](https://learn.adafruit.com/products/4540/guides)
Featured
### Adafruit NAU7802 24-Bit ADC - STEMMA QT / Qwiic
[Adafruit NAU7802 24-Bit ADC - STEMMA QT / Qwiic](https://www.adafruit.com/product/4538)
If you are feeling the stress and strain of ~~modern life~~ a Wheatstone bridge and you want to quantify it, this handy breakout will do the job, no sweat! The **Adafruit NAU7802** contains a super-high-resolution 24-Bit differential ADC with extra gain and calibration...
In Stock
[Buy Now](https://www.adafruit.com/product/4538)
[Related Guides to the Product](https://learn.adafruit.com/products/4538/guides)
Featured
### STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long
[STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210)
This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
In Stock
[Buy Now](https://www.adafruit.com/product/4210)
[Related Guides to the Product](https://learn.adafruit.com/products/4210/guides)
Featured
### 3 x AAA Battery Holder with On/Off Switch and 2-Pin JST
[3 x AAA Battery Holder with On/Off Switch and 2-Pin JST](https://www.adafruit.com/product/727)
This battery holder connects 3 AAA batteries together in series for powering all kinds of projects. We spec'd these out because the box is slim, and 3 AAA's add up to about 3.3-4.5V, a very similar range to Lithium Ion/polymer (Li-Ion) batteries and have an on-off switch. That makes...
In Stock
[Buy Now](https://www.adafruit.com/product/727)
[Related Guides to the Product](https://learn.adafruit.com/products/727/guides)
### USB cable - USB A to Micro-B
[USB cable - USB A to Micro-B](https://www.adafruit.com/product/592)
This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller
Approximately 3 feet / 1 meter long
In Stock
[Buy Now](https://www.adafruit.com/product/592)
[Related Guides to the Product](https://learn.adafruit.com/products/592/guides)
### Clear Adhesive Squares - 6 pack
[Clear Adhesive Squares - 6 pack](https://www.adafruit.com/product/4813)
**UGlu Dashes** are perfect for a variety of small projects. These adhesive squares provide a stronger bond to most surfaces and are cleaner and easier to remove without the wait, mess, or hassle.
Adheres to a wide variety of surfaces, including, but not limited...
In Stock
[Buy Now](https://www.adafruit.com/product/4813)
[Related Guides to the Product](https://learn.adafruit.com/products/4813/guides)
### Aluminum Extrusion Corner Brace Support (for 20x20)
[Aluminum Extrusion Corner Brace Support (for 20x20)](https://www.adafruit.com/product/1155)
Brace yourself! You'll definitely want to pick up a couple of these corner brace supports when working on a project with 20x20 extrusion. They're nice and solid, made of cast aluminum so they are stronger than extruded corner supports. Two holes, one in each corner allow you to easily...
In Stock
[Buy Now](https://www.adafruit.com/product/1155)
[Related Guides to the Product](https://learn.adafruit.com/products/1155/guides)
### Cross-Plate for 2020 Aluminum Extrusion
[Cross-Plate for 2020 Aluminum Extrusion](https://www.adafruit.com/product/1220)
Attach various pieces of 20mm slotted aluminum extrusion together with this 7-hole cross joining plate.
Measures 100mm long x 60mm wide, 4mm thick. 5.3m drill holes 20mm apart so you can use M4 or M5 screws. You'll want to use 10mm long screws to attach this to 20mm...
In Stock
[Buy Now](https://www.adafruit.com/product/1220)
[Related Guides to the Product](https://learn.adafruit.com/products/1220/guides)
### Wire Ferrule Kit - 800 pieces
[Wire Ferrule Kit - 800 pieces](https://www.adafruit.com/product/5131)
Crimping's not just for 80s hair metal bands! When your project requires repeated insertion and removal with minimal strain, why not check out the reliable wire ferrule? A wire ferrule is a tinned sleeve that once crimped, neatly holds all the pesky, individual strands of a...
In Stock
[Buy Now](https://www.adafruit.com/product/5131)
[Related Guides to the Product](https://learn.adafruit.com/products/5131/guides)
- [Next Page](https://learn.adafruit.com/clue-coffee-scale/features-and-operation.md)
## Guide Products
### Adafruit CLUE - nRF52840 Express with Bluetooth® LE
[Adafruit CLUE - nRF52840 Express with Bluetooth® LE](https://www.adafruit.com/product/4500)
Do you feel like you just don't have a CLUE? Well, we can help with that - get a CLUE here at Adafruit by picking up this sensor-packed development board. We wanted to build some projects that have a small screen and a lot of sensors. To make it compatible with existing projects, we made...
In Stock
[Buy Now](https://www.adafruit.com/product/4500)
[Related Guides to the Product](https://learn.adafruit.com/products/4500/guides)
### Clear Acrylic Enclosure + Hardware Kit for Adafruit CLUE
[Clear Acrylic Enclosure + Hardware Kit for Adafruit CLUE](https://www.adafruit.com/product/4675)
Here is a chic minimalist enclosure for your **CLUE** board! This case has been laser-cut specifically to accommodate the TFT display, tactile buttons, and capacitive pads.
And of course, we include mounting hardware so you can assemble it right onto your CLUE...
In Stock
[Buy Now](https://www.adafruit.com/product/4675)
[Related Guides to the Product](https://learn.adafruit.com/products/4675/guides)
### Strain Gauge Load Cell - 4 Wires - 1Kg
[Strain Gauge Load Cell - 4 Wires - 1Kg](https://www.adafruit.com/product/4540)
A strain gauge is a type of electronic sensor used to measure force or strain (big surprise there). They are made of an insulating flexible backing with a metallic foil pattern. The resistance of a strain gauge changes when force is applied and the...
Out of Stock
[Buy Now](https://www.adafruit.com/product/4540)
[Related Guides to the Product](https://learn.adafruit.com/products/4540/guides)
### Adafruit NAU7802 24-Bit ADC - STEMMA QT / Qwiic
[Adafruit NAU7802 24-Bit ADC - STEMMA QT / Qwiic](https://www.adafruit.com/product/4538)
If you are feeling the stress and strain of ~~modern life~~ a Wheatstone bridge and you want to quantify it, this handy breakout will do the job, no sweat! The **Adafruit NAU7802** contains a super-high-resolution 24-Bit differential ADC with extra gain and calibration...
In Stock
[Buy Now](https://www.adafruit.com/product/4538)
[Related Guides to the Product](https://learn.adafruit.com/products/4538/guides)
### STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long
[STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210)
This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
In Stock
[Buy Now](https://www.adafruit.com/product/4210)
[Related Guides to the Product](https://learn.adafruit.com/products/4210/guides)
### 3 x AAA Battery Holder with On/Off Switch and 2-Pin JST
[3 x AAA Battery Holder with On/Off Switch and 2-Pin JST](https://www.adafruit.com/product/727)
This battery holder connects 3 AAA batteries together in series for powering all kinds of projects. We spec'd these out because the box is slim, and 3 AAA's add up to about 3.3-4.5V, a very similar range to Lithium Ion/polymer (Li-Ion) batteries and have an on-off switch. That makes...
In Stock
[Buy Now](https://www.adafruit.com/product/727)
[Related Guides to the Product](https://learn.adafruit.com/products/727/guides)
### USB cable - USB A to Micro-B
[USB cable - USB A to Micro-B](https://www.adafruit.com/product/592)
This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller
Approximately 3 feet / 1 meter long
In Stock
[Buy Now](https://www.adafruit.com/product/592)
[Related Guides to the Product](https://learn.adafruit.com/products/592/guides)
### Clear Adhesive Squares - 6 pack
[Clear Adhesive Squares - 6 pack](https://www.adafruit.com/product/4813)
**UGlu Dashes** are perfect for a variety of small projects. These adhesive squares provide a stronger bond to most surfaces and are cleaner and easier to remove without the wait, mess, or hassle.
Adheres to a wide variety of surfaces, including, but not limited...
In Stock
[Buy Now](https://www.adafruit.com/product/4813)
[Related Guides to the Product](https://learn.adafruit.com/products/4813/guides)
## Related Guides
- [Introducing Adafruit CLUE](https://learn.adafruit.com/adafruit-clue.md)
- [Adafruit NAU7802 24-Bit ADC - STEMMA QT / Qwiic](https://learn.adafruit.com/adafruit-nau7802-24-bit-adc-stemma-qt-qwiic.md)
- [Remote Control Tree Ornament with Circuit Playground Express](https://learn.adafruit.com/remote-control-tree-ornament-with-circuit-playground-express.md)
- [NES Emulator for RP2040 & RP2350 DVI Boards](https://learn.adafruit.com/nes-emulator-for-rp2040-dvi-boards.md)
- [Adafruit Feather RP2040 with USB Type A Host](https://learn.adafruit.com/adafruit-feather-rp2040-with-usb-type-a-host.md)
- [Raspberry Pi SelfieBlock](https://learn.adafruit.com/selfieblock.md)
- [Motion Sensor Bat](https://learn.adafruit.com/motion-sensor-bat.md)
- [Adafruit ESP32-C6 Feather](https://learn.adafruit.com/adafruit-esp32-c6-feather.md)
- [No-Solder LED Disco Tie with Bluetooth](https://learn.adafruit.com/no-solder-circuit-playground-bluetooth-disco-tie.md)
- [Halloween Countdown Display Matrix](https://learn.adafruit.com/halloween-countdown-display-matrix.md)
- [AtariFruit 2600 Joystick](https://learn.adafruit.com/atarifruit-2600-joystick.md)
- [Pico W HTTP Server with CircuitPython](https://learn.adafruit.com/pico-w-http-server-with-circuitpython.md)
- [Goose Game M4SK Controller](https://learn.adafruit.com/goose-game-m4sk-controller.md)
- [Micro:bit Radio Control of Crickit Robotics](https://learn.adafruit.com/micro-bit-radio-control-of-crickit-robotics.md)
- [FunHouse Mail Slot Detector](https://learn.adafruit.com/funhouse-mail-slot-detector.md)
- [eInk / ePaper Weather Station](https://learn.adafruit.com/epaper-weather-station.md)
- [Bluetooth-Controlled Matrix LED Sign using Bluefruit Connect](https://learn.adafruit.com/bluetooth-controlled-matrix-led-sign-using-bluefruit-connect.md)