HX711 load cell amplifier
HX711 24-bit load cell amplifier: E+/E−/A+/A− load-cell pins, DT/SCK wiring, wire colours, 10 vs 80 samples per second and how to calibrate.
Community draft — report a mistake
3.3 V or 5 V? DT and SCK follow the module’s VCC. On 3.3 V boards, power the HX711 from 3.3 V; the load-cell excitation is then lower, but the readings are still fine after calibration.
A load cell is a metal bar with strain gauges that change resistance by tiny amounts under weight. The HX711 is a 24-bit amplifier and ADC built for exactly this: it turns millivolt changes into numbers your board can read on two digital pins.
The load-cell wire colours above are the most common, but they are not a standard — check your load cell’s label. Mount the bar so only one end is fixed and the weight presses on the other end, with the arrow pointing down.
Calibration is a two-step job: tare with nothing on the scale, then put a known weight on it and adjust the calibration factor until the reading matches. Store the factor in your sketch or EEPROM.
Pinout
| Pin | What it does |
|---|---|
E+ | Load-cell excitation + (usually red wire) |
E- | Load-cell excitation − (usually black wire) |
A- | Signal − channel A (usually white wire) |
A+ | Signal + channel A (usually green wire) |
B- | Channel B − (rarely used) |
B+ | Channel B + (rarely used) |
GND | Ground |
DT | Data out (to any digital pin) |
SCK | Clock in (to any digital pin) |
VCC | Supply, 2.6–5.5 V |
Library
HX711 Arduino Library by Bogdan Necula
Arduino IDE → Library Manager → search the name above. Each guide lists the exact version we compile against.
Use it with
- HX711 load cell amplifier with Arduino Nano Arduino C++
- HX711 load cell amplifier with Arduino Uno R3 Arduino C++
- HX711 load cell amplifier with ESP32 DevKit V1 Arduino C++
- HX711 load cell amplifier with ESP32-S3-DevKitC-1 Arduino C++
- HX711 load cell amplifier with NodeMCU ESP8266 Arduino C++
- HX711 load cell amplifier with Raspberry Pi Pico W MicroPython
Common errors
Reading drifts slowly
Normal warm-up drift for a minute or two after power-on. Tare after warm-up, and keep the load cell out of drafts and sun.
Weight goes negative when loaded
A+ and A− are swapped, or the load cell is mounted upside down. Swap the white and green wires, or use a negative calibration factor.
Values jump by thousands
Loose load-cell wires or a long, unshielded cable. Solder the joints and keep wires short.
Library waits forever in begin()
DT and SCK are swapped or not connected. The HX711 holds DT high until data is ready.