HX711 is a precision 24-bit analog-to-digital converter (ADC) designed for weight measurement applications. It is commonly used in electronic weighing scales and is capable of measuring small changes in weight with high accuracy. The HX711 chip is designed to work with strain gauge-based load cells, which convert the weight or force applied to them into an electrical signal that can be processed by the HX711. The HX711 provides amplification and analog-to-digital conversion of the load cell signal, and communicates the digital weight value to a microcontroller using a standard serial interface such as SPI or I2C. The HX711 is a popular choice for DIY electronic weighing scale projects due to its low cost, small size, and ease of use.
HX711 Pinouts
The HX711 chip has a total of 8 pins, which are:
- VCC: Power supply input (2.6V to 5.5V)
- GND: Ground
- DT: Data output pin for serial communication
- SCK: Clock input for serial communication
- A-: Negative input of the differential analog input
- A+: Positive input of the differential analog input
- E+ (or F+): Excitation positive input for the load cell
- E- (or F-): Excitation negative input for the load cell
Note that the labels E+ and E- are used when the HX711 is used in the common “bridge” configuration, while the labels F+ and F- are used when the HX711 is used in the “differential” configuration. The DT and SCK pins are used for serial communication with a microcontroller, while the A+ and A- pins are used for connecting the load cell.
How to make an Arduino weight measurement system using an HX711 and a load cell?
Materials needed:
- Arduino board (e.g. Uno or Nano)
- HX711 module
- Load cell (appropriate for your application)
- Breadboard or perfboard
- Jumper wires
- USB cable for Arduino programming and power
Steps:
- Connect the HX711 module to the Arduino board. Connect the VCC pin of the HX711 to the 5V pin of the Arduino, the GND pin to the GND pin of the Arduino, the DT pin to a digital pin (e.g. pin 2) of the Arduino, and the SCK pin to another digital pin (e.g. pin 3) of the Arduino.
- Connect the load cell to the HX711 module. Connect the load cell’s red wire to the E+ or F+ pin of the HX711 module, the black wire to the E- or F- pin of the HX711 module, and the white or green wire to the A- or A+ pin of the HX711 module (note: the polarity of the load cell wires may vary depending on the manufacturer).
- Download and install the HX711 library for Arduino. You can find this library in the Arduino Library Manager or download it from the GitHub repository.
- Write a simple Arduino sketch to read the weight from the load cell using the HX711 library. Here’s an example code:
#include <HX711.h>
HX711 scale;
void setup() {
Serial.begin(9600);
scale.begin(2, 3); // DT pin, SCK pin
}
void loop() {
float weight = scale.get_units();
Serial.print("Weight: ");
Serial.print(weight);
Serial.println(" kg");
delay(1000);
}
- Upload the code to the Arduino board and open the Serial Monitor in the Arduino IDE. You should see the weight readings in kilograms displayed in the Serial Monitor.
That’s it! You can now use this setup to create your own weight measurement projects, such as a digital kitchen scale or a DIY weigh-in station. Note that the calibration of the load cell may need to be adjusted for your specific application, and you can use the set_scale() and set_offset() functions of the HX711 library to calibrate the readings.
What is a Load Cell or Weight Sensor?
A load cell or weight sensor is a transducer that is used to convert a force or weight into an electrical signal that can be measured and analyzed. It typically consists of a metal structure or a strain gauge that is deformed under a load, causing a change in resistance that can be measured by an electrical circuit.
Load cells can be used in a variety of applications, such as weighing systems, force measurement, torque measurement, and pressure measurement. They come in various shapes and sizes, including beam, shear, compression, and tension types, and can be made of different materials depending on the application.
In weighing systems, load cells are used to measure the weight of an object by detecting the force exerted by the object on the load cell. They are commonly used in industrial scales, platform scales, and laboratory balances. The load cell output signal is typically amplified and processed by an analog-to-digital converter (ADC) to obtain a digital weight value that can be displayed or further processed by a microcontroller or computer.
Overall, load cells provide a reliable and accurate method for measuring weights and forces, making them an essential component in many industrial and scientific applications.
10 HX711 module projects Ideas:
- Digital kitchen scale: Build a digital scale that can accurately measure the weight of ingredients for cooking and baking.
- Smart pet feeder: Use an HX711 module to measure the weight of pet food in a container, and automatically dispense the right amount of food for your pet based on its weight and feeding schedule.
- DIY weigh-in station: Create a weight measurement system that can track your weight over time and display the data on a graph or chart.
- Load cell force sensor: Use an HX711 module to create a force sensor that can measure the force exerted on an object or surface.
- Smart plant pot: Measure the weight of a plant pot using an HX711 module and use the data to determine when the plant needs watering or fertilizing.
- Bike power meter: Use an HX711 module to measure the force applied to the pedals of a bicycle and calculate the power output of the cyclist.
- Smart trash bin: Measure the weight of a trash bin using an HX711 module and use the data to alert the user when the bin needs to be emptied.
- Automatic fish feeder: Use an HX711 module to measure the weight of fish food in a container, and automatically dispense the right amount of food for your fish based on its weight and feeding schedule.
- Homebrew beer scale: Build a digital scale that can accurately measure the weight of brewing ingredients for making beer at home.
- Smart luggage: Create a luggage scale that can accurately measure the weight of a suitcase or backpack, and alert the user when the weight exceeds the airline’s baggage allowance limit.
