Resistance Temperature Detector (RTD) circuit

The RTD module is currently is out of stock🙁.

Buy module and 3-wire Pt100 for $40

Buy module only for $25

Example uses: laboratory, hydroponics, aquarium, brewing

Easily meaure temperature with lab-quality accuracy.

Supports 2, 3, and 4 wire Pt100 and Pt1000 RTD temperature sensors. Use on-board jumpers to select sensor type and wiring - no soldering required. The SPI interface can communicate with almost any microcontroller.

Available with or without included Pt100 3-wire RTD. Connects directly to your device (eg Arduino, Raspberry Pi, or embedded) - no other parts required. Libraries and code samples are available for Python, Arduino/C++, and Rust. They provide easy setup, readings, and calibration.

We provide high-level drivers to make it easy to get started

Fully tested on Arduino, Raspberry Pi, and STM32

Why this instead of other RTD modules?

• No soldering required
• Supports both Pt1000 and Pt100
• Uses full-size terminals

Output pins are labeled on the board, as follows:

• +3V3: Power input
• MISO: SPI MISO
• CLK: SPI CLK
• CS: SPI chip select (any free GPIO pin)
• MOSI: SPI MOSI
• GND: Ground
• RDY: Optional: Connect to a free GPIO pin

Installing drivers

Arduino: From the Arduino IDE: Sketch → Include Library → Manage Libraries → select Anyleaf

C++: Download Anyleaf.cpp and Anyleaf.h from the C++ Github link below, and place them in your project directory

Python: Run sudo apt install python3-scipy, then pip3 install anyleaf. Ensure SPI is enabled.

Example code, and driver source

• Arduino and C++

• Python

• Rust

A minimal Arduino example

#include <Anyleaf.h>

Rtd sensor;

void setup(void) {
    Serial.begin(9600);

    // 3-wire Pt100, with CS connected to pin 10.
    sensor = Rtd(10, RtdType::Pt100, RtdWires::Three);
}

void loop(void) {
    Serial.print("Temp: "); Serial.println(sensor.read());
    delay(1000);
}

A miminal Raspberry Pi Python example

import time
import board
import busio
import digitalio
from anyleaf import Rtd, RtdType, RtdWires


def main():
    spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
    # 3-wire Pt100, with CS connected to pin 5.
    cs = digitalio.DigitalInOut(board.D5)
    sensor = Rtd(spi, cs, RtdType.PT100, RtdWires.THREE)  # 3-wire pt100

    while True:
        print(f"Temp: {sensor.read()} °C")
        time.sleep(1)


if __name__ == "__main__":
    main()

Datasheet

Specifications:

• Chip: Max31865
• Module dimensions: 45 × 35 × 15(height) mm
• Module weight: 15 grams
• Temperature precision: 0.03°C
• Temperature accuracy: 0.5°C and better
• Temperature Range: -200 to 550°C
• Digital precision: 15 bit
• Input voltage: 3.3V
• Mounting screws: 4 × M3, 6mm len (included)
• Sensor interface: 2, 3, or 4-wire screw terminal
• Power consumption: 375μA
• UPC / GTIN: 860004179030

Specifications pertaining to the optionally-included Pt100 only:

• Design: Class A Pt100 Platinum Resistance Temperature Device
• Resistance at 0°C: 100Ω
• Temperature Range: -200 to 850°C
• Probe dimensions: 100mm lengh × 3 mm radius
• Cable length: 1 m
• Connector: 3-wire space connectors
• Temperature range: 0-700°C

Compatible with the Mycodo Environmental Monitoring and Regulation System. If you're using a Raspberry Pi, this is a simple way to get it running with a GUI, charts, and logging. Just follow the installation instructions on that page, and add Max31865 as an input.