SparkFun
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 am...
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 digital supply.
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 colored RED, BLK, WHT, GRN and YLW. Each color corresponds to the conventional color 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 color coding.
Note: Special thanks to Bodge for supplying the Library for the HX711!
Jargon buster
Plain-language definitions for the technical terms used above.
- breakout
- A breakout is a small circuit board that makes a tiny or hard-to-solder component easier to connect to with standard pins. It matters because this OLED module can be wired into a microcontroller project without needing to solder directly to the display’s fine contacts.
- electromagnetic interference
- Electromagnetic interference is unwanted electrical noise from nearby devices, cables, or radio signals that can disturb a signal in a wire. Shielding helps reduce this noise, which matters for network adapters because cleaner signals are less likely to cause unreliable connections or data errors.
- GPIO
- General-purpose input/output pins are microcontroller pins you can set in software to read signals, switch devices on and off, or connect to peripherals. The number of GPIO pins matters because it limits how many buttons, LEDs, sensors, and other parts you can wire directly to the board.
- microcontroller
- A microcontroller is a small computer on a chip that runs your program and controls connected inputs and outputs. For this product, it is the part that reads buttons and sensors, drives the display and speaker, and communicates over Bluetooth.
- Shield
- An add-on board that plugs into a main controller board to give it extra features such as sensing, motor control or communication. Knowing a product supports shields helps you judge whether it can connect neatly into an existing maker-board setup.
- Strain gauge
- A sensor element that changes resistance when it is stretched or compressed. It is commonly used for measuring force, weight, or bending, and often needs precise differential measurement electronics like this ADC.
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SparkFun HX711 Load Cell Amplifier Schematic
Schematic · 58.6 KB · Click any page to view full size
HX711 Datasheet
Datasheet · 263.2 KB · Click any page to view full size
Supplier page — sparkfun.com
Supplier Description · 1.2 MB · Click any page to view full size
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