SparkFun Load Cell Amplifier - HX711

The SparkFun Load Cell Amplifier is a compact breakout board for the HX711 IC, designed to facilitate weight measurement by reading load cells. When connected to a microcontroller, it enables you to monitor the changes in the load cell's resistance, and after calibration, it provides highly accurate weight measurements. This feature makes it an ideal tool for building your own industrial scale, process control, or simple presence detection.

The SparkFun Load Cell Amplifier has been revamped based on customer feedback. The analog and digital supply have been separated, and a 3.3uH inductor and a 0.1uF filter capacitor have been added to the digital supply. If you're looking for more, consider the SparkFun Qwiic Scale. It boasts all the features of the HX711, plus additional library support, a genuine I2C interface, and it requires no soldering.

The HX711 utilizes a two-wire interface (Clock and Data) for communication. It can be used with any microcontroller's GPIO pins, and there are numerous libraries available to simplify reading data from the HX711. For more information, check the hookup guide.

Load cells connect to the HX711 through a four-wire Wheatstone bridge configuration. These wires are usually colored RED, BLK, WHT, GRN, and YLW, each representing a different function. The YLW pin is an optional input that isn't connected to the strain gauge but is used to ground and shield against external EMI (electromagnetic interference). Please note that the color coding might vary slightly among different load cells.

Special thanks to Bodge for providing the Library for the HX711.

The SparkFun Load Cell Amplifier features an operation voltage of 2.7V--5V and an operation current of less than 1.5mA. It offers a selectable 10SPS or 80SPS output data rate and simultaneous 50 and 60Hz supply rejection.

For more information about the SparkFun Load Cell Amplifier, you can refer to the schematic, Eagle Files, Hookup Guide, Getting Started with Load Cells guide, and Datasheet (HX711). You can also find design files and example code on GitHub, as well as the Library.