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====== lamaPLC: Max31865 RTD to Digital Converter - PT100/PT1000 Platine ======
{{ :sensor:max31865_1.png?200|Max31865 RTD to Digital Converter}}
The MAX31865 is an easy-to-use resistance-to-digital converter designed for platinum resistance temperature detectors (RTDs). An external resistor determines the sensitivity for the RTD used, and a precision delta-sigma ADC converts the RTD resistance ratio to the reference resistance into a digital output. The MAX31865’s inputs are protected against overvoltage faults up to 45V. It also includes programmable detection for RTD and cable open or short conditions.

  * Simple Conversion of Platinum RTD Resistance to Digital Value
  * Supports 100Ω to 1kΩ (at 0°C) Platinum RTDs (PT100 to PT1000)
  * Compatible with 2-, 3-, and 4-Wire Sensor Configurations
  * [[com:basic_spi|SPI]]-Compatible Interface
  * Voltage for module: **3-5 V DC**

===== Pins =====
  * Vin: This is the power pin. Since the chip operates at 3 VDC, we have included an on-board voltage regulator that accepts **3-5V DC** and safely steps it down. To power the board, supply it with the same voltage as your microcontroller's logic level — for example, use 5V for a 5V microcontroller, such as an Arduino.
  * 3Vo: This is the 3.3V output from the voltage regulator; you can draw up to 100mA from this if needed.
  * GND: Common ground for power and logic.
  * SCK: This is the SPI Clock pin, an input to the chip.
  * SDO: This is the Serial Data Out / Microcontroller In Sensor Out pin, used for data sent from the MAX31865 to your processor.
  * SDI: This is the Serial Data In / Microcontroller Out Sensor In pin, used for data sent from your processor to the MAX31865.
  * CS: This is the Chip Select pin; drop it low to start an SPI transaction. It is an input to the chip.
  * RDY (Ready): This is a data-ready indicator pin. You can use this pin to speed up your reads if you are writing your own driver. Our Arduino driver doesn't use it to save a pin.

===== Configuration =====
{{ :sensor:max31865_2.png?200|MAX31865 configuration}}

  * By default, the sensor is configured for 4-wire RTD operation, but can be set for 2 or 3-wire. For a 4-wire setup, leave the jumpers as they are!

  * For 3-wire usage: Solder the jumper labeled 2/3 Wire closed and cut the wire connecting the left side of the 2-way jumper just above Rref. Then, solder the right side labeled 3 closed.

  * For 2-wire use: solder the two triangular jumpers below the terminal blocks closed, or connect short wire jumpers between the two terminal blocks on each side (essentially jumpering the two right-side terminal holes together, and the same for the left side).

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{{page>sensor:pt100}}

===== SPI Wiring =====
Since this is an SPI-capable sensor, we can use either hardware or software SPI. To ensure consistent wiring across all Arduinos, we'll start with 'software' SPI. The following pins should be used:

  * Connect the **Vin** to the **power supply**; 3.3V or 5V is fine. Use the same voltage as the microcontroller's logic. For most Arduinos, that is 5V.
  * Connect **GND** to **common** power/data ground.
  * Connect the **CLK** pin to Digital **#13**
  * Connect the **SDO** pin to Digital **#12**
  * Connect the **SDI** pin to Digital **#11**
  * Connect the **CS** pin to Digital **#10**

===== Arduino library =====
To start reading sensor data, install the **Adafruit MAX31865** library from the Arduino library manager.
> https://www.adafruit.com/products/3328

===== Sources =====
[[https://learn.adafruit.com/adafruit-max31865-rtd-pt100-amplifier|Adafruit MAX31865 RTD PT100 or PT1000 Amplifier]] \\

{{tag>MAX31865 RTD PT_100 PT_1000 temperature SPI Platinum Arduino Adafruit}}

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