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The SparkFun Qwiic Scale is a small breakout board for the NAU7802 that allows you to easily read load cells to accurately measure the weight of an object. B...

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The SparkFun Qwiic Scale is a small breakout board for the NAU7802 that allows you to easily read load cells to accurately measure the weight of an object. By connecting the board to your microcontroller you will be able to read the changes in the resistance of a load cell and, with some calibration, you'll be able to get very accurate weight measurements. This can be handy for creating your own industrial scale, process control or simple presence detection. Utilizing our handy Qwiic system, no soldering is required to connect it to the rest of your system. However, we still have broken out 0.1"-spaced pins in case you prefer to use a breadboard.

By connecting a load cell to the Qwiic Scale you will be able to translate sensor data into something your microcontroller can read. The NAU7802 is an ADC with built in gain and I2C output to amplify and convert the readings from a standard load cell. A load cell is basically a device that translates pressure or force into electrical signals. In most cases this signal is very small and needs to be amplified. There are many popular chips that read the change and amplify it, but the NAU7802 goes one step further and converts everything to a true I2C output (attached to a Qwiic connector).

The board provides a four spring terminal to connect your load cell with no soldering required. In addition to the I2C pins, the board also breaks out an interrupt pin and AVDD to the edge of the board. The differential input signals (plus a second set of input signals) are broken out to the middle of the board, as well.

The SparkFun Qwiic connect system is an ecosystem of I2C sensors, actuators, shields and cables that make prototyping faster and less prone to error. All Qwiic-enabled boards use a common 1mm pitch, 4-pin JST connector. This reduces the amount of required PCB space, and polarized connections mean you can’t hook it up wrong.

GET STARTED WITH THE QWIIC SCALE HOOKUP GUIDE

Jargon buster

Plain-language definitions for the technical terms used above.

ADC
An analogue-to-digital converter reads a changing voltage and turns it into a number the microcontroller can use. It matters when connecting analogue sensors such as light, sound, or variable-resistor sensors.
breakout
A breakout board carries a small or fine-pitched component and brings its connections out to standard, breadboard- and header-friendly pins. Describing a part as a breakout means it can be wired into a project without soldering directly to the component's tiny contacts.
Differential input
A measurement method where the board reads the voltage difference between two input wires instead of measuring one wire compared with ground. This is useful for small sensor signals and noise reduction, but both input voltages still need to stay within the board’s allowed range.
I2C
I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
microcontroller
A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
PCB
A printed circuit board (PCB) is a board, usually rigid, with etched copper tracks that connect electronic components together without loose wiring. Components are mounted on the board and signals route between them through the copper layout.
Qwiic
Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.

Qwiic Scale Schematic

Schematic · 91.6 KB · Click any page to view full size

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NAU7802 Datasheet

Datasheet · 1.4 MB · Click any page to view full size

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Supplier page — sparkfun.com

Supplier Description · 966.8 KB · Click any page to view full size

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