Qwiic Scale Hookup Guide

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Contributors: Nate
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Introduction

There are a variety of exciting projects around the measurement of the weight of an object. Whether it measuring if a chicken has left the coup, the bees have left at dawn, or automating the filling of liquids; being able to digitally interface to a scale is key. The Qwiic Scale is an incredibly easy way to read scales and their inner bits, load cells.

SparkFun Qwiic Scale - NAU7802

SparkFun Qwiic Scale - NAU7802

SEN-15242
$14.95
5

We’ve designed the Qwiic Scale so that little or no soldering is required. We’ve even written an Arduino library so that to get the weight of an object it’s as easy as:

language:c
float weight = myScale.getWeight(); 

Required Materials

If you’re just getting started we recommend obtaining a digital scale and hacking into it. This is because it can be tricky to correctly mechanically attach a load cell.

Bathroom scale with insides exposed

This low-cost scale already has the load cell properly mounted. Ready to be modified to an I2C addressable one.

Alternatively, if you have a unique application, or if this is not your first rodeo measuring weight, checkout the load cells we carry in a variety of shapes and capacities to create your own solution.

We're going to assume you’re just beginning with scales; we recommend you pick out a scale that has roughly the capacity of weight you want to measure. For example, a bathroom scale is best at measuring ~20lbs up to ~300lbs. If you’re trying to measure a few ounces then don’t use a bathroom scale, get a kitchen food scale instead.

Additionally, you’ll need an item of known weight. This will be used to calibrate your DIY scale. Depending on the accuracy needed for your project, you can use any object (can of soda 394 or 355.1g, dumbell, bag of flour, etc) as long as you know the weight or have an additional scale from which you can get a known weight.

Various items around the house with a known weight

10 pound plate, 4lbs flour, Diet coke, 100g calibration weight

Suggested Reading

If you’re unfamiliar with load cells, jumper pads, or I2C be sure to checkout some of these foundational tutorials.

Analog to Digital Conversion

The world is analog. Use analog to digital conversion to help digital devices interpret the world.

I2C

An introduction to I2C, one of the main embedded communications protocols in use today.

Getting Started with Load Cells

A tutorial defining what a load cell is and how to use one.

How to Work with Jumper Pads and PCB Traces

Handling PCB jumper pads and traces is an essential skill. Learn how to cut a PCB trace, add a solder jumper between pads to reroute connections, and repair a trace with the green wire method if a trace is damaged.

If you aren't familiar with the Qwiic system, we recommend reading here for an overview.

Qwiic Connect System
Qwiic Connect System