Introduction: Thermocouple Type K - Arduino ESP32

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Intro - ESP 32 microcontroller circuit was set up with a HS711 amplifier to read a thermocouple type K for a reference input from digital thermometer.

Supplies

  1. 1 - Breadboard
  2. 1 - Thermocouple type K
  3. 1 - HS711 Amplifier
  4. 1 - Arduino ESP 32
  5. 1 - DS18B20 Digital Thermometer
  6. 3 - resistors
  7. 5 - male to female jumper wires
  8. 3 - female to female jumper wires
  9. 1 - USB to ESP 32 connector
  10. 2 - hook up clips (female)
  11. 1 - hook up clip (male)

Step 1: Connect Electronic Technology

From ESP 32

  1. D25 -> SCK on HS711 Amplifier
  2. D26 -> DT on HS711 Amplifier
  3. VIN -> VCC on HS711 Amplifier
  4. GND -> GND on HS711 Amplifier
  5. D27 -> spot A2 on breadboard
  6. GND -> spot A1 on breadboard
  7. 3V3 -> spot A3 on breadboard



From HS711 Amplifier

  1. A+ -> small prong on DS18B20 digital thermometer
  2. A- -> large prong on DS18B20 digital thermometer
  3. E+ -> spot F1 on breadboard
  4. E- -> spot F6 on breadboard



From DS18B20 digital thermometer

  1. Small prong -> F3 on breadboard



On breadboard

  1. GND - spot A1 on breadboard
  2. D27 - spot A2 on breadboard
  3. 3V3 - spot A3 on breadboard
  4. Resistor (23k ohms) B2 to B3
  5. Thermocouple (semi circle outward from rest of connections) in C1, C2, C3
  6. E+ - spot F1 on breadboard
  7. E- - spot F6 on breadboard
  8. Small prong - F3 on breadboard
  9. Resistor (23k ohms) G1 to G3
  10. Resistor (23k ohms) G3 to G6

Step 2: Initialize Arduino ESP 32

Using a USB plugin, plug in the Arduino to your computer.

Initialize the Arduino by downloading Arduino IDE (arduino.cc/en/software)

Under boards manager, search and install Arduino ESP32 Boards by Arduino

Click on ‘select board’, select port, search for and select ‘DOIT ESP32 DEVKIT V1’

Step 3: Run Code

Under Files, Examples, HX711 Arduino Library, HX711_Basic_Example


#include "HX711.h"


// HX711 circuit wiring

const int LOADCELL_DOUT_PIN = 26;

const int LOADCELL_SCK_PIN = 25;


HX711 scale;


const float Vref = 2.0; // Reference voltage in volts

const int gain = 128;  // Gain factor for HX711

const long maxBits = 8388608; // 2^23, the maximum code for 24-bit ADC


void setup() {

 Serial.begin(57600);

 scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);

}

void loop() {


 if (scale.is_ready()) {

  long reading = scale.read();


  // Calculate Vtc from the code

  float Vtc = (float(reading) * Vref) / (gain * maxBits);


  // Print raw reading and calculated voltage

  Serial.print("HX711 reading: ");

  Serial.print(reading);

  Serial.print(" => Vtc: ");

  Serial.print(Vtc, 6); // 6 decimal places for precision

  Serial.println(" V");


 } else {

  Serial.println("HX711 not found.");

 }

 delay(1000);

}


For LOADCELL_DOUT_PIN = 26 and LOADCELL_SCK_PIN = 25

Run code

Attachments

Step 4: Solve for Voltage of Thermocouple

Update code to find V_tc

V_ref = 2V, gain = 128, 24 bits-sign = 2^23

V_tc = (code x V_ref) / (gain x 2^23)

Add code for solving and press upload

Using Thermocouple Type K reference table, use V_tc to find temperature