I explain how to connect a four-wire load cell to the HX711 amplifier module and how to read the weight value with an Arduino.
Disclosure: Bear in mind that some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. Keep in mind that I link these companies and their products because of their quality and not because of the commission I receive from your purchases. The decision is yours, and whether or not you decide to buy something is completely up to you.
Arduino with Load Cell and HX711 Amplifier (Digital Scale)
In this guide, you'll learn how to create a digital scale with the Arduino using a load cell and the HX711 amplifier. First, you'll learn how to wire the load cell and the HX711 amplifier to the Arduino to build a scale. Then, we'll show you how to calibrate the scale, and a simple example to get the weight of objects. Later, we'll also add a display to show the measurements and a button to measure the scale.
A load cell converts a force into an electrical signal that can be measured. The electrical signal changes proportionally to the force applied. There are different types of load cells: strain gauges, pneumatic, and hydraulic. In this tutorial, we'll cover strain gauge load cells.
Strain gauge load cells are composed of a metal bar with attached strain gauges (under the white glue in the picture above). A strain gauge is an electrical sensor that measures force or strain on an object. The resistance of the strain gauges varies when an external force is applied to an object, which results in a deformation of the object's shape (in this case, the metal bar). The strain gauge resistance is proportional to the load applied, which allows us to calculate the weight of objects.
Usually, load cells have four strain gauges hooked up in a wheatstone bridge (as shown below) that allow us to get accurate resistance measurements. For a more detailed explanation of how strain gauges work, read this article.
HX711 Amplifier
The HX711 amplifier is a breakout board that allows you to easily read load cells to measure weight. You wire the load cell wires on one side, and the microcontroller on the other side. The HX711 communicates with the microcontroller using two-wire interface (Clock and Data).
You need to solder header pins on the GND, DT, SCK, and VCC pins to connect to the Arduino. I soldered the load cell wires directly to the E+, E-, A-, and A+ pins. The load cell wires were very thin and fragile, be careful when soldering not to damage the wires.
Setting Up the Load Cell
Our load cell kit came with two acrylic plates and some screws to set up the load cell as a scale. You can use wood plates or 3D-print your own plates.
You should attach the plates to the load cell in a way that creates a strain between the opposite ends of the metal bar. The bottom plate holds the load cell, and the upper plate is where you place the items.
I explain how to connect a four-wire load cell to the HX711 amplifier module and how to read the weight value with an Arduino.
Disclosure: Bear in mind that some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. Keep in mind that I link these companies and their products because of their quality and not because of the commission I receive from your purchases. The decision is yours, and whether or not you decide to buy something is completely up to you.
Arduino with Load Cell and HX711 Amplifier (Digital Scale)
In this guide, you'll learn how to create a digital scale with the Arduino using a load cell and the HX711 amplifier. First, you'll learn how to wire the load cell and the HX711 amplifier to the Arduino to build a scale. Then, we'll show you how to calibrate the scale, and a simple example to get the weight of objects. Later, we'll also add a display to show the measurements and a button to measure the scale.
A load cell converts a force into an electrical signal that can be measured. The electrical signal changes proportionally to the force applied. There are different types of load cells: strain gauges, pneumatic, and hydraulic. In this tutorial, we'll cover strain gauge load cells.
Strain gauge load cells are composed of a metal bar with attached strain gauges (under the white glue in the picture above). A strain gauge is an electrical sensor that measures force or strain on an object. The resistance of the strain gauges varies when an external force is applied to an object, which results in a deformation of the object's shape (in this case, the metal bar). The strain gauge resistance is proportional to the load applied, which allows us to calculate the weight of objects.
Usually, load cells have four strain gauges hooked up in a wheatstone bridge (as shown below) that allow us to get accurate resistance measurements. For a more detailed explanation of how strain gauges work, read this article.
HX711 Amplifier
The HX711 amplifier is a breakout board that allows you to easily read load cells to measure weight. You wire the load cell wires on one side, and the microcontroller on the other side. The HX711 communicates with the microcontroller using two-wire interface (Clock and Data).
You need to solder header pins on the GND, DT, SCK, and VCC pins to connect to the Arduino. I soldered the load cell wires directly to the E+, E-, A-, and A+ pins. The load cell wires were very thin and fragile, be careful when soldering not to damage the wires.
Setting Up the Load Cell
Our load cell kit came with two acrylic plates and some screws to set up the load cell as a scale. You can use wood plates or 3D-print your own plates.
You should attach the plates to the load cell in a way that creates a strain between the opposite ends of the metal bar. The bottom plate holds the load cell, and the upper plate is where you place the items.
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