Circuit Documentation

Summary

This circuit is designed to measure temperature using an RTD PT100 sensor interfaced with an Adafruit MAX31865 RTD Sensor Breakout. The data is processed and displayed using a NodeMCU V3 ESP8266 microcontroller. The NodeMCU reads the temperature data from the MAX31865 and outputs it via the serial monitor.

Component List

1. Adafruit MAX31865 RTD Sensor Breakout

   • Description: A breakout board for the MAX31865 RTD-to-Digital converter, used to interface with RTD sensors like the PT100.
   • Pins: VIN, GND, 3.3V, SCLK, SDO, SDI, CS, DRDY, FORCE+, RTDIN+, RTDIN-, FORCE-

2. NodeMCU V3 ESP8266

   • Description: A low-cost Wi-Fi microcontroller with GPIO, ADC, and serial communication capabilities.
   • Pins: A0, GND, VU, S3, S2, S1, SC, S0, SK, 3V3, EN, RST, Vin, D0, D1, D2, D3, D4, D5, D6, D7, D8, RX, TX

3. RTD PT100

   • Description: A platinum resistance temperature detector (RTD) with a resistance of 100 ohms at 0°C.
   • Pins: 1, 2

Wiring Details

Adafruit MAX31865 RTD Sensor Breakout

• VIN: Connected to 3V3 of NodeMCU V3 ESP8266
• GND: Connected to GND of NodeMCU V3 ESP8266
• SCLK: Connected to D5 of NodeMCU V3 ESP8266
• SDO: Connected to D6 of NodeMCU V3 ESP8266
• SDI: Connected to D7 of NodeMCU V3 ESP8266
• CS: Connected to D8 of NodeMCU V3 ESP8266
• FORCE+: Connected to pin 2 of RTD PT100
• RTDIN+: Connected to pin 2 of RTD PT100
• RTDIN-: Connected to pin 1 of RTD PT100
• FORCE-: Connected to pin 1 of RTD PT100

NodeMCU V3 ESP8266

• 3V3: Connected to VIN of Adafruit MAX31865 RTD Sensor Breakout
• GND: Connected to GND of Adafruit MAX31865 RTD Sensor Breakout
• D5: Connected to SCLK of Adafruit MAX31865 RTD Sensor Breakout
• D6: Connected to SDO of Adafruit MAX31865 RTD Sensor Breakout
• D7: Connected to SDI of Adafruit MAX31865 RTD Sensor Breakout
• D8: Connected to CS of Adafruit MAX31865 RTD Sensor Breakout

RTD PT100

• Pin 1: Connected to RTDIN- and FORCE- of Adafruit MAX31865 RTD Sensor Breakout
• Pin 2: Connected to RTDIN+ and FORCE+ of Adafruit MAX31865 RTD Sensor Breakout

Code Documentation

sketch.ino

#include <Adafruit_MAX31865.h>

// MAX31865 pins
#define MAX_CS   8 // Chip Select
#define MAX_MOSI 7 // Master Out Slave In
#define MAX_MISO 6 // Master In Slave Out
#define MAX_CLK  5 // Clock

// Create an instance of the sensor (RTD type, wires)
Adafruit_MAX31865 max31865 = Adafruit_MAX31865(MAX_CS, MAX_MOSI, MAX_MISO, MAX_CLK);

void setup() {
  Serial.begin(9600); // 115200
  // Initialize the MAX31865 (2-wire PT100)
  max31865.begin(MAX31865_2WIRE);
}

void loop() {
  // Read temperature
  float temperature = max31865.temperature(100.0, 430.0); // 100.0: PT100; 430: Reference resistance
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");

  delay(5000); // 1 second delay
}

This code initializes the MAX31865 sensor and reads the temperature from the RTD PT100 sensor. The temperature is then printed to the serial monitor every 5 seconds.