Arduino with an RTD?

[huntb]

I'm wondering if anyone is using an Arduino with an RTD temp sensor? I want to use one of the Auber 1/2" NPT RTD's for my project and was wondering if anyone has done this and what they used for signal conversion. I'm thinking about using a MAX31865 and using SPI to read the signal.

Any input?

 

[Hex23]

I'm wondering if anyone is using an Arduino with an RTD temp sensor? I want to use one of the Auber 1/2" NPT RTD's for my project and was wondering if anyone has done this and what they used for signal conversion. I'm thinking about using a MAX31865 and using SPI to read the signal.

Any input?

I've done this exact thing with an Uno (including an Auber RTD). Of course since the 31865 is SMT, you'll need to find a way to mount it. I used these guys: http://www.proto-advantage.com/store/datasheets/IPC0012.pdf. They'll solder it for you - you just provide a ref to the digikey part, etc. But I'm sure there are other options, esp if you want to etch your own board and have a toaster oven for reflow

It's all in a Arduino case like this: http://www.adafruit.com/product/337 and coupled with this data logger: http://www.adafruit.com/products/1141 and this LCD: http://www.adafruit.com/products/181

I'll send you my code if you're interested. I haven't written code for the datalogger yet, but it's got all the core RTD features available (Callendar–Van Dusen via table lookup)

 

[huntb]

I've done this exact thing with an Uno (including an Auber RTD). Of course since the 31865 is SMT, you'll need to find a way to mount it. I used these guys: http://www.proto-advantage.com/store/datasheets/IPC0012.pdf. They'll solder it for you - you just provide a ref to the digikey part, etc. But I'm sure there are other options, esp if you want to etch your own board and have a toaster oven for reflow

It's all in a Arduino case like this: http://www.adafruit.com/product/337 and coupled with this data logger: http://www.adafruit.com/products/1141 and this LCD: http://www.adafruit.com/products/181

I'll send you my code if you're interested. I haven't written code for the datalogger yet, but it's got all the core RTD features available (Callendar–Van Dusen via table lookup)

Wow, this is incredible! I would love to see your code, if you can PM it to me or I can give you my email if you wanted to send it to me. Do you have a build thread for it?

 

[Hex23]

Ya I thought it was amazingly serendipitous that someone else had the same idea. Unfortunately I have no build thread and (sheepishly) maybe no schematic. Though not that hard to reverse engineer. The only other "special" aspect I remember is the 5V to 3.3V translation. If you had a 3.3V arduino and no reason to interface to other 5V components like I did, that would obviously be easier. In my case it wasn't terribly difficult (just uses an OTS part from Spark fun), but I do seem to recall some surprises. I'll PM you the code later today, and I might just put it up on Bitbucket too.

 

[thekraken]

I'd like to take a look at that code too if your willing to share.

 

[Hex23]

https://bitbucket.org/hexamer/max31865forarduino

Let me know if you have any questions. Pardon all the debug statements. The code probably also relies on some libraries for the RTC and LCD, but it's been so long ago I don't remember the details.

I'll provide some details on the hardware build later, though you can probably deduce some of it through the code.

 

[Hex23]

These weren't available when I was first dabbling with the 31865, but for just a few dollars more, you can get a board that has includes a local power supply and level shifters: http://www.playingwithfusion.com/productview.php?pdid=25

Edit: Something you might want to investigate though ... I now remember my pains with level shifting were with a TXB010X device (this one: https://www.sparkfun.com/products/11771). I ultimately switched to this: (https://www.sparkfun.com/products/12009). I see other folks mentioning issues with TXB010X chips and the MAX31865 - possibly incompatible drive strength. The design I referenced above uses a TXB0108 and it appears no other pullups, etc. So I'm not sure how that design succeeds - maybe in a limited context?

 

[huntb]

These weren't available when I was first dabbling with the 31865, but for just a few dollars more, you can get a board that has includes a local power supply and level shifters: http://www.playingwithfusion.com/productview.php?pdid=25

Edit: Something you might want to investigate though ... I now remember my pains with level shifting were with a TXB010X device (this one: https://www.sparkfun.com/products/11771). I ultimately switched to this: (https://www.sparkfun.com/products/12009). I see other folks mentioning issues with TXB010X chips and the MAX31865 - possibly incompatible drive strength. The design I referenced above uses a TXB0108 and it appears no other pullups, etc. So I'm not sure how that design succeeds - maybe in a limited context?

Good to know, I really appreciate the info. I shouldn't have a problem with the schematic now that I have the code. Thank you again!