Connecting 3-Wire RTD Pt100 to Arduino Uno: A Comprehensive Guide

Connecting a 3-wire RTD Resistance Temperature Detector Pt100 sensor to an Arduino Uno involves detailed circuit design to ensure accurate temperature readings. This guide will walk you through the necessary components, wiring, and code to successfully connect and read temperature data from a Pt100 RTD using an Arduino Uno.

Components Required

Arduino Uno 3-wire RTD Pt100 sensor RTD-to-Digital converter (e.g., MAX31865) Breadboard and jumper wires (Optional) Power supply if needed

Wiring Diagram

For a straightforward setup using the MAX31865 RTD-to-Digital converter, follow the wiring diagram below:

Red (R1) - Connect to A on MAX31865 White (R2) - Connect to B on MAX31865 Black (R3) - Connect to C on MAX31865 VIN - Connect to 5V on Arduino GND - Connect to GND on Arduino SCK - Connect to Pin 13 or any other pin for SPI SCK MISO - Connect to Pin 12 or any other pin for SPI MISO MOSI - Connect to Pin 11 or any other pin for SPI MOSI CS - Connect to Pin 10 Chip Select can be any digital pin

Arduino Code Example

To read the temperature from the MAX31865 using Arduino, you can use the following example code. Make sure to install the Adafruit MAX31865 library via the Library Manager in the Arduino IDE.

include Adafruit_MAX31865.h#define MAX31865_CS     10  // Chip select pin for MAX31865#define MAX31865_MISO   12  // MISO pin#define MAX31865_MOSI   11  // MOSI pin#define MAX31865_SCK    13  // SCK pinAdafruit_MAX31865 rtd  Adafruit_MAX31865(MAX31865_CS, MAX31865_MISO, MAX31865_MOSI, MAX31865_SCK);void setup {  (9600);  (MAX31865_3WIRE);  // Set to 3-wire configuration}void loop {  uint16_t rtdResistance  ();  float temperature  rtd.temperature100.0 * 430.0 / 100.0;  // 100 ohm RTD 430 ohm reference resistor  (rtdResistance);  (temperature);  delay(1000);  // Wait for a second before next reading}

Explanation of the Code

Library Initialization - The Adafruit_MAX31865 library is initialized with the chip select pin. Setup Function - The begin function is called with MAX31865_3WIRE to specify that you are using a 3-wire RTD. Loop Function - The RTD resistance is read and converted to temperature using the specified reference resistance values for the Pt100. The results are printed to the Serial Monitor.

Notes

Be sure to calibrate your setup if needed as the accuracy can depend on several factors including the wiring and the environment. Ensure that the MAX31865 is properly powered and that the connections are secure to avoid erroneous readings.

This setup will allow you to read temperature values accurately from a 3-wire Pt100 RTD using an Arduino Uno. If you have further questions or need assistance with specific parts of the setup, feel free to ask!