Arduino, Thermocouples, MAX6675 and SPI – The Fine Points

Just install the library and you’re done. Or so you might think …
↓↓↓ Complete description, time index and links below ↓↓↓

You want to measure temperatures up to 1.000°C/1.800°F with an Arduino? Use a MAX6675 thermocouple-to-digital module! They’re a cheap, supported and easy solution, featuring a SPI-compatible interface.

However, the raw data from the MAX6675 needs some filtering. And while there is a MAX6675 library available for the Arduino, there are reasons not to use it. Also, be aware of shorts you might create using multiple thermocouples.

00:00 Intro – where I left off during a mailbag video
02:02 Code and circuit – from the internet: fast and easy
05:06 Data – lots of noise and not very precise
08:55 Filtering – a simple (modified) moving average does the job
13:29 Timing – the MAX6675 is not the fastest
18:18 Multiplying – the number of sensors, because it’s easy enough
23:26 Shorting – things out using thermocouples
29:19 Rewriting – the Arduino MAX6675 library for real SPI

#robertssmorgasbord #tutorials #tutorial #how-to #Arduino #thermocouple #MAX6675 #SPI

[poirou]

Cannot even describe how helpful this video is. Thank you very much <3

[andymouse]

I came back to this one for a refresher!...Its a favorite because it has so much info about the module that is hard to find...cheers.

[MrEdwardhartmann]

Great video - 14k views and only 226 likes?? I don't get it - this was a wonderfully clear and helpful video - it should have at least 5000 likes by now.

[_ahwaszargar]

I really appreciate the time you have invested in making this video.Considering how very well written it was coupled with easy explanantion thank you Sir So much for this video it was a pure gold mine of information.I want to know How you came to the conclusion of choosing this particular formula for moving avergae because i have seen a different one for it .Also Sir why did u choose mov_avg =-100 in start

[nalinux]

I love your meter !
I had the Dm27XL :)
Worked correctly for 30 years before I lost it.

[andymouse]

This is fascinating to me as I have used this module myself for a homemade tandoor (oven) I also had to average out the data but my maths is rubbish, so I just added together 10 readings and divided it, also I only update my Oled display every couple of seconds this works fine for the oven (great chicken!) I have also run into the "ground" issue. Not using the library is something i'm gonna go away and play with Its quite simple the way you put it...cheers.

[lampartzjardu]

Thank you so much for this tutorial. You much speeded up my project <3

[jamesmac]

I don't know who is enjoying it more, you by making the video or me by watching your video :) How can I contact you regarding technical questions?

[bintangaldoni]

Hi robert Thank you very much for the video its reallay give me a lot of new knowlade. i have a questions about the thermocouple with the max6675, now im in a project to make deep frying machine and i've used the thermocouple. everytimes the themocouple touching the survaces of this machine which is made by stainless steel its get failure for the thermocouple read the temperature.
i hope you have any sugest or recommendations for it, should i do special methode for this thermocouple max6675 or i must to use other module for it?

thanks, have a nice day

[patrickmclaughlin]

Thank You for the video.
So if you have multiple thermocouples you would have to insulate them from each other? It seems like that might effect the accuracy of the readings?
Guess I would have to experiment with them to figure something out.
Thanks again, great info on using the arduino and thermocouples.

[NicedayNice-wpbp]

Hello, nice explanation. For detecting fire, what is the best sensor for arduino uno?

[e.a.debeijer]

Thank you very much for this informative video. I am a NOOB when it comes down to electronics but i am able to apply "The science" when it has been shown to me :) This helps me a lot in further building my smoker temperature meter where i want to be able to measure the temperature in de the smoker as well as the core temperature of whatever i have in my oven at thst time. Now i am just looking for a way to connect an o-led display to show the values...

[niswanthskumar]

Sir, first of all thanks a lot for the video. Iam making a similar temp Data acquisition system with arduino. I have to measure 2.5m underwater. Should i use a thermocouple or thermistor? Please reply.

[piyushsharma]

Sir can you please tell that, 19:22 will this method work if i want to have 8 max6675 modules and also want to add a 1602 lcd display shield on arduino mega 2560?

when there will be a voltage problem?

[ovi_]

Hi, great video and very instructional as well. However, I wonder what modification in code as well as in hardware you need to do if you only have the MAX31855 modules instead? I have several but none of the MAX 6675.
And by the way, my modules are 3.3V but the Arduino is 5V so, I'm thinking, I will probably need to use some sort of logic level shifter modules (bidirectional maybe? I'm not sure) to communicate with the MCU. Also, another question is what library? The Adafruit one or...is there any other I can use? It would be great if you could make a video with the above modules or perhaps some ideas on how I need to do it? Thank you.

[edgarinv]

Great video! I wanted to read the temperature of 3 fermenting vesels using pt100's I think your video help me a lot. Is it similar when using multiple MAX31865 ?
one other question, If I wanted to display the temperatures on an OLED screen will it work also with SPI ?

[mumbaiverve]

Hi Robert,
In a moving average as you have implemented, by choosing alpha=0.1, the sample size automatically becomes 10 ? So for eg, if i chose 0.01, would it mean i am averaging over 100 samples ? I am writing some code to calculate the average value of a mains voltage sine wave, so could i use something like this for that ?
Thanks for your great videos :)

[spacetime]

awesome vid! thanks so much. one question: how did you claculate error of +-2.25C from LSD of +-9.0 thanks.

[ricg]

Hi Robert,
The max6675 data sheet seems to indicate 3.3v to 5v can be used.
The library was apparently written with 5v in mind ? I get correct temps when using 5v (comparing to a ds18b20).
My readings using 3.3v are about 10-12 degrees Fahrenheit higher, but i'm not sure if simply subtracting this differential will give me a correct reading over a large temperature range.
Your thoughts are appreciated. i hope it's as simple as subtracting, but usually things like this are much more complicated than they appear. thank you.

[rohitbhosle]

Thanks for detailed video about module really helpful 🙏
I want to measure temperature of copper pipe at 4 different location so if I connect 4 Thermocouples on pipe then I will experience short problem. Can you suggest any solution like Thermocouples whose tip is electrically isolated or something like that
Thanks