Weight sensor HX711 (bar-type)
https://www.aliexpress.com/item/1005006827930173.html
https://www.amazon.de/-/en/gp/product/B079FQNJJH/
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.
flowchart LR
subgraph ESP32
VCC[3.3V]
GND
GPIO16
GPIO17
end
subgraph HX711
E+
E-
A+
A-
GND2[GND]
DT
SCK
VCC2[VCC]
end
VCC <--> VCC2
GND <--> GND2
GPIO16 <--> DT
GPIO17 <--> SCK
E+ <--> Red
E- <--> Black
A+ <--> Green
A- <--> White
subgraph LoadCell
Red
Green
Black
White
end
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:
flowchart TD
subgraph ESP32
VCC[3.3V]
GND[GND]
GPIO16[GPIO16 - DT1]
GPIO17[GPIO17 - SCK1]
GPIO18[GPIO18 - DT2]
GPIO19[GPIO19 - SCK2]
GPIO21[GPIO21 - DT3]
GPIO22[GPIO22 - SCK3]
GPIO23[GPIO23 - DT4]
GPIO25[GPIO25 - SCK4]
end
subgraph HX711_1[HX711 #1 - Front Left]
DT1[DT]
SCK1[SCK]
VCC1[VCC]
GND1[GND]
E1+[E+]
E1-[E-]
A1+[A+]
A1-[A-]
end
subgraph HX711_2[HX711 #2 - Front Right]
DT2[DT]
SCK2[SCK]
VCC2[VCC]
GND2[GND]
E2+[E+]
E2-[E-]
A2+[A+]
A2-[A-]
end
subgraph HX711_3[HX711 #3 - Back Left]
DT3[DT]
SCK3[SCK]
VCC3[VCC]
GND3[GND]
E3+[E+]
E3-[E-]
A3+[A+]
A3-[A-]
end
subgraph HX711_4[HX711 #4 - Back Right]
DT4[DT]
SCK4[SCK]
VCC4[VCC]
GND4[GND]
E4+[E+]
E4-[E-]
A4+[A+]
A4-[A-]
end
subgraph LoadCell1[Load Cell 1 - Front Left]
Red1[Red - E+]
Black1[Black - E-]
White1[White - A-]
Green1[Green - A+]
end
subgraph LoadCell2[Load Cell 2 - Front Right]
Red2[Red - E+]
Black2[Black - E-]
White2[White - A-]
Green2[Green - A+]
end
subgraph LoadCell3[Load Cell 3 - Back Left]
Red3[Red - E+]
Black3[Black - E-]
White3[White - A-]
Green3[Green - A+]
end
subgraph LoadCell4[Load Cell 4 - Back Right]
Red4[Red - E+]
Black4[Black - E-]
White4[White - A-]
Green4[Green - A+]
end
%% Power connections
VCC -.-> VCC1
VCC -.-> VCC2
VCC -.-> VCC3
VCC -.-> VCC4
GND -.-> GND1
GND -.-> GND2
GND -.-> GND3
GND -.-> GND4
%% Digital connections
GPIO16 --- DT1
GPIO17 --- SCK1
GPIO18 --- DT2
GPIO19 --- SCK2
GPIO21 --- DT3
GPIO22 --- SCK3
GPIO23 --- DT4
GPIO25 --- SCK4
%% Load cell connections
E1+ --- Red1
E1- --- Black1
A1+ --- Green1
A1- --- White1
E2+ --- Red2
E2- --- Black2
A2+ --- Green2
A2- --- White2
E3+ --- Red3
E3- --- Black3
A3+ --- Green3
A3- --- White3
E4+ --- Red4
E4- --- Black4
A4+ --- Green4
A4- --- White4
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-