HX711 Load Cell Module

What is the HX711 Module?

The HX711 Load Cell Amplifier is a precision analog-to-digital converter (ADC) designed specifically for load cells (weight sensors).

It amplifies extremely small signals from a load cell and converts them into digital values that microcontrollers (like Arduino) can read.

How It Works

A load cell uses the strain gauge principle:

• When weight is applied the metal deforms slightly

• This changes the resistance of strain gauges

• The output is a very small voltage (in millivolts)

The HX711:

• Amplifies this tiny signal (gain = 32, 64, or 128)

• Converts it using a 24-bit ADC

• Sends digital data to a microcontroller

Pin Configuration Pin Function VCC Power supply (2.7V 5V) GND Ground DT (DOUT) Data output SCK (CLK) Clock input

Load Cell Connections:

(Some load cells may vary in color)

Working Flow

Weight Applied'Load Cell (strain changes)Small Analog Voltage (mV)HX711 Amplifies Signal24-bit ADC Conversion'Digital Output to Microcontroller

Key Features

• 24-bit high-resolution ADC

• Built-in pry

• Two selectable channels (A & B)

• Simple 2-wire interface (DT & SCK)

Important Concepts

1. Gain Selection

• Channel A: Gain 128 or 64

• Channel B: Gain 32

Higher gain more sensitivity

2. Calibration

Raw values from HX711 are not in kg/grams.

You must:

• Take a known weight

• Calculate a calibration factor

• Apply it in code

Applications

• Digital weighing scales

• Smart shopping carts

• Industrial weight measurement

• Robotics (force sensing)

• Laboratory measurements

Advantages

• Very high precision (24-bit)

• Cheap and widely available

Limitations

• Requires calibration

• Sensitive to noise and vibration

• Slower sampling rate (~1080 Hz)

• Needs stable power supply

Example Use with Arduino

Basic idea:

• Connect DT digital pin

• Connect SCK digital pin

• Use HX711 library

• Read values and convert to weight

Real-Life Working Example

When you place an object:

• Load cell bends slightly

• Resistance changes

• Voltage changes (~mV)

• HX711 amplifies and converts

• Ar