SparkFun Load Cell Amplifier - HX711

The SparkFun Load Cell Amplifier is a small breakout board for the HX711 IC that allows you to easily read load cells to measure weight. By connecting the amplifier to your microcontroller you will be able to read the changes in the resistance of the 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.

This version of the SparkFun Load Cell Amplifier features a few changes that you specifically asked for! We have separated the analog and digital supply, as well as added a 3.3uH inductor and a 0.1uF filter capacitor for the digital supply. Need even more? Check out the SparkFun Qwiic Scale. It has all the features of the HX711 but with additional library support, a true I2C interface, and no soldering required!

The HX711 uses a two-wire interface (Clock and Data) for communication. Any microcontroller’s GPIO pins should work, and numerous libraries have been written, making it easy to read data from the HX711. Check the hookup guide below for more information.

Load cells use a four-wire Wheatstone bridge configuration to connect to the HX711. These are commonly coloured RED, BLK, WHT, GRN and YLW. Each colour corresponds to the conventional colour coding of load cells:

• Red (Excitation+ or VCC)
• Black (Excitation- or GND)
• White (Amplifier-, Signal- or Output-)
• Green (A+, S+ or O+)
• Yellow (Shield)

The YLW pin acts as an optional input that is not hooked up to the strain gauge but is utilized to ground and shield against outside EMI (electromagnetic interference). Please keep in mind that some load cells might have slight variations in colour coding.

Get Started with the HX711 Load Cell Amplifier Guide

Features

• Operation Voltage: 2.7V--5V
• Operation Current: < 1.5mA
• Selectable 10SPS or 80SPS output data rate
• Simultaneous 50 and 60Hz supply rejection

Resources

• Schematic
• Eagle Files
• Hookup Guide
• Getting Started with Load Cells
• Datasheet (HX711)
• GitHub (Design Files & Example Code)
• GitHub (Library)