Circuit Documentation

Summary

The circuit in question is designed to measure physical parameters such as weight and environmental conditions like temperature and humidity. It consists of a load cell interfaced with an HX711 bridge sensor interface for weight measurement, an ESP32 microcontroller for processing and communication, and an ENS160+AHT21 sensor module for measuring temperature and humidity. A Mini-360 DC-DC Step Down Buck Converter is used to regulate the power supply to the 3.3V required by the sensors and the ESP32 from a 12V power source.

Component List

Load Cell - Red/white/black/green

A transducer that converts force into an electrical signal. It has four pins: E+, A-, E-, and A+.

HX711 - Bridge Sensor Interface

A precision 24-bit analog-to-digital converter (ADC) designed for weigh scales and industrial control applications to interface directly with a bridge sensor. It has ten pins: E+, E-, A-, A+, B-, B+, GND, DATA (OUT), SCK (CLOCK IN), and 3.3/3.5V Supply.

ESP32

A powerful microcontroller with Wi-Fi and Bluetooth capabilities. It has a variety of GPIO pins, including EN, VP, VN, D34, D35, D32, D33, D25, D26, D27, D14, D12, D13, GND, VIN, 3V3, D15, D2, D4, RX2, TX2, D5, D18, D19, D21, RX0, TX0, D22, D23, and BOOT.

ENS160+AHT21

A sensor module that combines gas and environmental sensing. It has seven pins: VIN, 3V3, GND, SCL, SDA, ADD, CS, and INT.

Mini-360 DC-DC Step Down Buck Converter

A compact module that converts a higher voltage DC input to a lower voltage DC output. It has four pins: Input -, Input +, Output +, and Output -.

12V Power Supply

A power source that provides a 12V output. It has two pins: + and -.

Wiring Details

Load Cell - Red/white/black/green

• E+ connected to HX711 E+
• A- connected to HX711 A-
• E- connected to HX711 E-
• A+ connected to HX711 A+

HX711 - Bridge Sensor Interface

• E+, E-, A-, A+ connected to Load Cell
• GND connected to Mini-360 DC-DC Step Down Buck Converter Output - and ENS160+AHT21 GND
• DATA (OUT) connected to ESP32 D12
• SCK (CLOCK IN) connected to ESP32 D13
• 3.3/3.5V Supply connected to Mini-360 DC-DC Step Down Buck Converter Output + and ENS160+AHT21 3V3

ESP32

• D12 connected to HX711 DATA (OUT)
• D13 connected to HX711 SCK (CLOCK IN)
• D21 (I2C SDA) connected to ENS160+AHT21 SDA
• D22 (I2C SCL) connected to ENS160+AHT21 SCL

ENS160+AHT21

• GND connected to Mini-360 DC-DC Step Down Buck Converter Output - and HX711 GND
• 3V3 connected to Mini-360 DC-DC Step Down Buck Converter Output + and HX711 3.3/3.5V Supply
• SDA connected to ESP32 D21
• SCL connected to ESP32 D22

Mini-360 DC-DC Step Down Buck Converter

• Input - connected to 12V Power Supply -
• Input + connected to 12V Power Supply +
• Output + connected to HX711 3.3/3.5V Supply and ENS160+AHT21 3V3
• Output - connected to HX711 GND and ENS160+AHT21 GND

12V Power Supply

• • connected to Mini-360 DC-DC Step Down Buck Converter Input +
• • connected to Mini-360 DC-DC Step Down Buck Converter Input -

Documented Code

#include <HX711.h>
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_AHTX0.h>

// HX711 pins
#define HX711_DOUT 12
#define HX711_SCK 13

// I2C pins for ENS160+AHT21
#define I2C_SDA 21
#define I2C_SCL 22

// Create instances
HX711 scale;
Adafruit_AHTX0 aht;

void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);
  
  // Initialize HX711
  scale.begin(HX711_DOUT, HX711_SCK);
  Serial.println("HX711 initialized.");

  // Initialize I2C for ENS160+AHT21
  Wire.begin(I2C_SDA, I2C_SCL);
  if (!aht.begin()) {
    Serial.println("Failed to find AHT sensor!");
    while (1) delay(10);
  }
  Serial.println("AHT sensor initialized.");
}

void loop() {
  // Read weight from HX711
  if (scale.is_ready()) {
    long reading = scale.read();
    Serial.print("HX711 reading: ");
    Serial.println(reading);
  } else {
    Serial.println("HX711 not found.");
  }

  // Read temperature and humidity from AHT21
  sensors_event_t humidity, temp;
  aht.getEvent(&humidity, &temp);
  Serial.print("Temperature: ");
  Serial.print(temp.temperature);
  Serial.println(" degrees C");
  Serial.print("Humidity: ");
  Serial.print(humidity.relative_humidity);
  Serial.println("% rH");

  // Delay between readings
  delay(2000);
}

This code is designed to run on the ESP32 microcontroller. It initializes communication with the HX711 and the ENS160+AHT21 sensor, reads data from both sensors, and outputs the readings to the Serial Monitor. The HX711 is used for weight measurement, while the ENS160+AHT21 sensor provides temperature and humidity readings.