DIY thermocouple interface

[Agrajag]

While phidget/tc4 look great they are fairly expensive options (also the tc4 doesn't always seem to be available, and when it is, shipping is $$$$ to Australia) so I looked into making one myself with an arduino. The bits required are readily available and very cheap. A MAX6675 breakout is ~$2 and an arduino copy is about $10. If you want to use the arduino for controlling other parts of your roaster (fan/stove) I'd recommend getting an arduino mega (~$20) as you might run out of pins.

There is a max6675 library for arduino, so reading the temperature from it is very simple. To interface with artisan you can write your own program that opens the serial port to the arduino and get your arduino code to write the temps back, artisan can read that output from the "External Program" option (see the help button next to that option.)

The only issue I had was with grounding issues when I turned on the fan/huky motor (even though I'm using ungrounded TCs, so not sure exactly where the issue is). Attaching a wire from the huky body to a ground pin on the arduino solved this though, I get smooth/accurate readings now.

I'm happy to expand on any of the above if anyone has any questions/wants more detail, thought I'd just let others know this is an option.

[brian p]

I am about to buy the Huky and I was going to go with the Phidget. This seems like a much better option. I never liked the idea of controlling the fan speed with a variac. I'm not a computer novice, nor am I with wiring/soldering etc, but I am with arduino. Will I just need the Mega 2560, and three MAX6675 breakouts? Is it possible to run the three thermocouples as well as control fan speed all on the same Arduino?

I'm thinking down the road it might be cool to have the thermocouples display temp on an lcd screen so it could be used as a stand alone system as well as with artisan. Not sure if that's even possible, any thoughts on this?

Thanks for the great info!

[monkey_lever]

What you are describing is very similar to the TC4 board. If you can solder could be a good option.

[brian p]

Yes, it sure does! Just had a look at the TC4, it's quite the project. I think I'm gonna keep things 'simple' and stick with the Arduino. Going with Agrajag's design, it is only going to cost around $50....and that's with a stepper motor (future considerations)

[Agrajag]

Will I just need the Mega 2560, and three MAX6675 breakouts? Is it possible to run the three thermocouples as well as control fan speed all on the same Arduino?

Yep shouldn't be a problem, I've got 2 TC interfaces + fan control + motor control and have pins to spare

I'm thinking down the road it might be cool to have the thermocouples display temp on an lcd screen so it could be used as a stand alone system as well as with artisan. Not sure if that's even possible, any thoughts on this?

Yes, entirely possible. I haven't setup an LCD as I always use artisan but that should be pretty simple.

[brian p]

I've ordered the interface parts yesterday. I'm going to experiment with everything and see if I can get it working before I get the roaster. I have a few thermocouples here already. I'm heading to Taiwan after Chrismas for non-coffee roaster related reasons. Hopefully when I get back I'll have my new Huky with me! If I have any issues I hope you don't mind offering advice! I think I'm more excited about the Ardunio than the roaster!

[cgriffith]

any updates?

I had played around with exact arduino+Max6675 TC before going Huky thinking I would mod a popper.  It worked fine with "RoastLogger".  But I am curious about the idea of controlling the fan.