MAX31855K with Arduino Uno

Sensors Environmental
1

Hi, I am pretty inexperienced with coding and I have a quick question regarding the MAX31855K thermocouple breakout board(https://learn.sparkfun.com/tutorials/ma … okup-guide). I recently purchased one and I am trying to use it with an Arduino Uno. However, when I load the example code, I get the error message “all bits were 0 … fishy”. I have the VCC going to the 3.3V pin on the Arduino Uno and GND going to the ground pin. Pins 10, 11, 12, and 13 are connected to CS, NC, SO, and SCK respectively. From my understanding, these are the pins typically used for SPI communication by the Arduino Uno. I am sure I am missing something simple, any help would be greatly appreciated. Here is the link to the github library for the sensor: (https://github.com/sparkfun/MAX31855K_T … rduino/src)

2

Can you send a photo showing how the board is connected to your Uno?

3

Yes here are some pictures of the connections on the board:

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4

OK, I see you’ve connected power to 3.3 volts, but the data lines for this board can’t exceed 3.3 volts and you have it connected to a Uno that has 5 volt data. Unfortunately that has most likely fried the MAX31855K chip and that’s why you’re seeing the error you’re getting. :frowning:

We recommend using a 3.3 volt [Arduino Pro Mini along with a [3.3 volt FTDI with this particular product.](https://www.sparkfun.com/products/13746)](https://www.sparkfun.com/products/11114)

5

Oh no that is unfortunate. Correct me if I am wrong, but the actual thermocouple should be ok, it would just be the board that is fried? Is there another breakout board that could be used with a 5V signal or a way to modify the uno digital pins to output 3.3V?

6

The thermocouple itself should be just fine, it’s just the MAX31855K that’s going to have issues.

You could use a logic level converter in between the Uno and MAX31855K to shift 5 volt logic to 3.3 volt logic though. Checkout the [Logic Level Converter - Bi-Directional and it’s [hookup guide for details on how to connect the three devices.](https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide)](https://www.sparkfun.com/products/12009)