MAX6675 Thermocouple breakout board (TC-6675)

In order to improve and verify the performance of my Reprap Mendel extruder I decided to build a system based on a K-Type thermocouple. I ordered some samples of a MAX6675 from Maxim Integrated Products. I decided to use this chip over the Analog Devices AD595 out of curiosity as it was new to me and due to the 12-bit digital output. Although plenty of breakout boards already exist for this product I decided to design my own based around this PCB-mount thermocouple connector. I like the idea of being able to simply unplug a thermocouple and quickly plug another one in so the use of a standard miniature socket sounds like a pretty good idea to me. It makes switching between probes a breeze and allows me to use cheap thermocouple probes from Maplin

I haven’t tested this board yet so I’ll have to update the post later after I’ve had a chance to play with some ferric chloride.

Having stood back from the design for about 3 seconds it occurs to me that I should probably combine this with my ATTINY45 USB Key project to make a standalone Thermocouple to USB converter, but who has the time 🙂 .

All files are Creative Commons Attribution-Share Alike 2.0
TC-6675, Schematic (PDF)
Eagle Library (MAX6675ISA+ and RS#3817564)
TC-6675 Schematic (EAGLE)
TC-6675 PCB layout (EAGLE)

8 Responses to “MAX6675 Thermocouple breakout board (TC-6675)”

  1. renoir says:

    Liking your work. I’m sailing a very similar course to yours, I’ve just posted an arduino mega shield for the RepRap/Mendel and a thermocouple board was next on my list! Thanks for covering the ground for me!



  2. Nick says:

    Just got this PCB made and tested yesterday. Works perfectly! Tested with an Arduino Duemilanove and

  3. […] testing the PCB with the library code everything works fine. The arduino returns a reading every second and […]

  4. […] on PORTB and also via the ISP connector. An example breakout PCB for the MAX6675 was published here. Default wiring from the this PCB to the AVR Butterfly Logger is given […]

  5. zachschi says:

    Hi, is the large blue area the ground plane? I am just curious as I am designing a thermostat and I read that a large ground plane helps with accuracy in temp reading. Thank you and excellent post!

  6. Nick says:

    Yep, thats the ground plane and it’s there for that exact reason. The overall accuracy is around ±4°C and can have a couple of degrees of noise.

  7. […] I have finally motivated myself to publish my firmware and PCB designs for the MLMC on github. The design is functional and I have a set of five modules chained together sitting on my workbench. They happily display the current temperature via an Arduino and the MAX6675 based Thermocouple board I designed previously. […]

  8. […] The MAX6675 from Maxim is an SPI Bus based thermocouple convertor that I built a breakout board for a while back. You can find out more information about that project in this earlier post. […]

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