Single Thermocouple Interface

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Version 1.3 Assembled

The single thermocouple interface was made out of the need to interface a microcontroller to a thermocouple. One of the popular chips to perform a thermocouple to digital conversion is the MAX6675. While this is a great little chip it is a small surface mount part and therefore difficult to solder. The thermocouple interface board not only helps with having the chip broken out to a simple 0.1" header, but also provides a mini-thermocouple connector to easily interface to a thermocouple. Thermocouples are not designed to be soldered directly to a PCB and this provides a good solid connection, while also using the proper metals in the connector required for a thermocouple connection.

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Contents

Tutorial

It is simple to get everything up and running.

  1. Install a header or solder jumper wires to the pin connections
  2. Connect a K-Type Thermocouple to the PCB Thermocouple Connector use a Thermocouple Wire Connector if necessary
  3. Wire the necessary connections to an Arduino or other microcontroller, the bare minimum connections ar +V, GND, SCK, SO, CS
  4. CAUTION: The MAX31855 is for 3.3V only! If connecting to a 5V system, you must use a level shifter. See MAX31855 with 5V for more details.
  5. If using an Arduino, load one of the samples from the MAX6675 Arduino Library and you should see temperature information in the serial console. With other microcontollers you can access the chip using a standard SPI interface. See MAX31855 for more details.

Version 2.0 (5V) (In Production)

This version of the board is a 5V compatible version of the interface. It is equipped with a MAX31855, along with the necessary voltage regulation and level shifting to allow for it to be directly hooked up to a 5V microcontroller similar to an Arduino. The board comes fully assembled and includes a male and female header. Licensed under OSHW

Board Specs

Eagle Files

Version 1.3 (3.3V) (In Production)

Version 1.3 Assembled

This revision changed from the MAX6675 to the new MAX31855 chip. It has more accuracy and a better temperature range. The footprint and fixturing holes have remained the same, but the board layout modified to make a better connection between the thermocouple connector and the MAX31855. They were move closer together and larger traces between the chip and connector. This should allow for better CJC, and more accuracy. The board comes fully assembled along with a male and female header, and a 4050 level shifter chip. Licensed under OSHW

Board Specs

Eagle Files


Version 1.2

The current version of the board did not make many changes from V1.1. The changes were mainly related to the manufacturing. The PCB dimensions were better specified in the gerber files sent to fab resulting in better board routing. The previous version was router slightly smaller than specified. The solder mask was also updated to correct for some errors and spacing.

Board Specs

Eagle Files


Version 1.1

Version 1.1 PCB and Assembled

The next version made some major changes based on some feedback of the original version. The additions included:

Board Specs

Eagle Files


Version 1.0

Version 1.0 PCB

The original version of this board was built as a simple breakout interface for the MAX6675. The first attempt to do this was using a SOIC to DIP adapter board. While this worked, it did not provide a reliable connection for a thermocouple. The solution was to use a PCB Thermocouple Connector.

Board Specs

Eagle Files


Software

See MAX6675 Arduino Library for code examples.

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