Measuring temperatures from -250C to +1600C with AVR-T32U4 Arduino Leonardo and MOD-TC-MK2-31885 + thermocouple


MOD-TC-MK2-31885 is UEXT module which uses MAX31885 and allow temperatures in range -250C to +1600C to be measured with proper thermocouple.

For this demo we use TC-K-TYPE which is low cost K-type thermocouple.

When the thermocouple is connected pay attention that it have polarity i.e. if your measurements start to decrease when you increase the thermocouple end temperature you have to swap the thermocouple wires to the connector.

Another issue we got with Arduino 1.0.4 is that Serial print from time to time stop working on Leonardo and several uploads usually solve the problem, we guess this is some USB port problem and Leonardo is not properly enumerated as CDC serial port every time.

Also I2C library on Leonardo sometimes beahve weird and in this case you have to decrease I2C speed a bit. So if the sketch do not work correctly just edit TWI_FREQ to 80000L in:


#ifndef TWI_FREQ
 #define TWI_FREQ 100000L

You can watch the demo at this video:

As you can see there are two temperatures which are measured: the temperature on the thermocouple TC and the internal MAX31855 temperature INT (i.e. cold end thermocouple temperature).

Also MAX31885 recognize if the thermocouple is disconnected, shorted or connected to VCC.

The demo code is at GitHub:

6 Comments (+add yours?)

  1. Sebastian
    May 29, 2013 @ 15:06:03

    This is a fine solution, but I guess it would be even more convenient to use of the TC-MK2-31885 board had a receptacle for the thermocouple’s original plug.


  2. adminVasi
    May 29, 2013 @ 18:31:55

    Great stuff, thank you!


  3. Vasi
    May 29, 2013 @ 18:33:17

    Sorry about the ID, it was added by wordpress after asked me to log into my account…


  4. thomaswolfgangschubert
    Jun 12, 2013 @ 12:41:02

    this looks interesting. the datasheet says the precision is 0.25°C. is there a way to increase the resolution? We want to measure skin temperature, and would appreciate a finer resolution.


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  6. se
    Aug 16, 2014 @ 21:46:39

    can you share the schematic?


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