Weight sensor HX711 (bar-type)

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Wiring

Single Load Cell Setup

HX711 Load Cell Amplifier:

E = Excitation. E+ (Red) and E- (Black) are the excitation wires for the load cell, providing the voltage that powers the load cell.
A = Amplifier. A+ (White) and A- (Green) are the signal wires from the load cell, carrying the differential signal that the HX711 amplifies.

Four Load Cells Setup (for complete beehive weight measurement)

Yes, you can connect 4 weight sensors to a single ESP32! Each load cell needs its own HX711 amplifier. Here's how the connections work:

Alternative Wiring (Shared SCK): You can share the SCK (clock) line between all HX711 modules to save ESP32 pins. In this case, you'd only need 5 pins total (1 shared SCK + 4 separate DT pins):

ESP32 GPIO17 → All HX711 SCK pins (shared)
ESP32 GPIO16 → HX711 #1 DT
ESP32 GPIO18 → HX711 #2 DT  
ESP32 GPIO21 → HX711 #3 DT
ESP32 GPIO23 → HX711 #4 DT
3.3V → All HX711 VCC pins
GND → All HX711 GND pins

Features

Two selectable differential input channels

On-chip active low noise PGA with selectable gain of 3264 and 128

On-chip power supply regulator for load-cell and ADC analog power supply

On-chip oscillator requiring no external component with optional external crystal

On-chip power-on-reset

Simple digital control and serial interface: pin-driven controlsno programming needed

Selectable 10SPS or 80SPS output data rate

Simultaneous 50 and 60Hz supply rejection

Current consumption including on-chip analog power supply regulator: normal operation < 1.5mApower down < 1uA

Operation supply voltage range: 2.6 ~ 5.5V

Operating Temperature Range:-20 degree ~ +85 degree

Connection Summary

For 4-sensor beehive scale setup:

Load Cell Position	HX711 Module	ESP32 DT Pin	ESP32 SCK Pin	Load Cell Wires
Front Left	HX711 #1	GPIO16	GPIO17	Red→E+, Black→E-, White→A-, Green→A+
Front Right	HX711 #2	GPIO18	GPIO19*	Red→E+, Black→E-, White→A-, Green→A+
Back Left	HX711 #3	GPIO21	GPIO22*	Red→E+, Black→E-, White→A-, Green→A+
Back Right	HX711 #4	GPIO23	GPIO25*	Red→E+, Black→E-, White→A-, Green→A+

*Can be shared (all connected to GPIO17) to save pins.

Power connections:

ESP32 3.3V → All HX711 VCC pins
ESP32 GND → All HX711 GND pins

Arduino Code Example:

#include "HX711.h"

// Define pins for each HX711
#define DT1 16
#define SCK1 17
#define DT2 18  
#define SCK2 19  // or 17 if sharing SCK
#define DT3 21
#define SCK3 22  // or 17 if sharing SCK
#define DT4 23
#define SCK4 25  // or 17 if sharing SCK

// Create HX711 instances
HX711 scale1, scale2, scale3, scale4;

void setup() {
  Serial.begin(115200);
  
  // Initialize each scale
  scale1.begin(DT1, SCK1);
  scale2.begin(DT2, SCK2);
  scale3.begin(DT3, SCK3);
  scale4.begin(DT4, SCK4);
  
  // Calibration factors (determine experimentally)
  scale1.set_scale(2280.f);
  scale2.set_scale(2280.f);
  scale3.set_scale(2280.f);
  scale4.set_scale(2280.f);
  
  // Tare (zero) all scales
  scale1.tare();
  scale2.tare();
  scale3.tare();
  scale4.tare();
}

void loop() {
  float weight1 = scale1.get_units(10);  // Average of 10 readings
  float weight2 = scale2.get_units(10);
  float weight3 = scale3.get_units(10);
  float weight4 = scale4.get_units(10);
  
  float totalWeight = weight1 + weight2 + weight3 + weight4;
  
  Serial.printf("Corner weights: %.2f, %.2f, %.2f, %.2f kg\n", 
                weight1, weight2, weight3, weight4);
  Serial.printf("Total hive weight: %.2f kg\n", totalWeight);
  
  delay(1000);
}

Red to E+

Black to E-

Green to A+

White to A-

Alternative

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Wiring​

Single Load Cell Setup​

Four Load Cells Setup (for complete beehive weight measurement)​