Arduino temp probe K type or RTD ???

Can some people with experience please way in on whether or not it is better to use K type or RTD temp probes with your arduino? And how you wired yours up and how it works would be appreciated too. Thanks. I'm planning on buying one of the above types from Auber, but can't decide which is better.

 

While the Arduino like the BrewTroller is a worthy platform, it will not directly interface with either type K or RTD probes. Here is where you should look for a probe for your application under temperature probes for brewtroller, http://www.brewershardware.com/Temperature-Sensors/

 

I have some prototype copper coming in for a three channel TC K and and a three channel RTD module. This will allow the Arduino/Brewtroller platforms more options for temp probes. I'll make a post when I get them in and tested.

 

Please do. I'd love to be able to use my existing RTDs if I decide to move to the BrewTroller.

 

Yeah, I was in the same boat and thats why I designed the RTD modules. figured some folks with TCs would like to play too so I made one for that.

 

Awesome! I've been amassing a ton of samples from several IC vendors looking for the right combination of signal conditioners, reference voltage controllers, and ADCs to build such a beast. If you come up with something simple and cheap I'd be excited to see/use it.

 

Anybody thought about building boards for the 1 wire analog I/O chips to interface with the Arduino board, possibly one with analog output capability.

 

That's what these are, No analog output though. You looking for something 0-5v/4-20ma?

 

I have nearly completed what I can do for the automated system remotely, and am looking for another project to take up the spare time while in Arizona. Looking ahead for simpler automation platform that could output 0-10volts for proportional control, and interface with other types of analog sensors. Seems to be a gap between the Arduino capabilities and the needs for an advanced control platform with analog control capabilities without going to PLC hardware.

 

For a 3rd option, I've been messing w/ the one-wire temp sensors as of late:
One Wire Digital Temperature Sensor - DS18B20
All you have to do is download a couple libraries, wire it up (extremely simple wiring), and you're good to go.
More info on the arduino site: http://www.arduino.cc/playground/Learning/OneWire

 

Yeah, thats kind of the defacto sensor people use with the 8bit AVRs.

 

I'm using the DS18B20 in my fermentation monitor and I am very happy with it. You can read a rundown on how I am using it here, although it is still a work in progress. I should have source code for both the Arduino and a C# application that logs/displays the results up there soon. I just need to clean it up a bit first.

 

PCBs should be here in a week and components are on their way.

 

Very cool, keep us posted. And we need pictures, lol.

Ron

 

Here they are built up.
The OneWire communications are reporting. Haven't tested to see if they actually measure anything yet.

 

Is that one of the heat shielded thermowell's from Brewers Hardware? Do you just have one of the one wire therms tucked in? I have three of the DS18S20 on the way from Digikey and I am trying to figure out how I could incorporate it into a kettle and run it to my arduino.

 

If you're willing to do a little work, there are a bagillion options out there for temperature probes that will interface to an ardrunio. A lot of the chip manufacturers will actually send you samples of them if you ask.

In general I think it's a smart idea to have digital signals running between your arduino and whatever sensor you're using. They'll be less susceptible to noise than an analog value would be, which will make a lot of difference if you have a pump and / or an electric heating element.

If you're specifically interested in interfacing with a thermocouple, I would suggest the MAX6674 (or MAX6675 - it has larger range but less accuracy). There's a good writeup of the arduino software here:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1230859336

You can also get samples of the chips from Maxim:
http://www.maxim-ic.com/datasheet/index.mvp/id/3194
http://www.maxim-ic.com/datasheet/index.mvp/id/3149

The chips only require one external component (a 0.1uF capacitor to filter the supply voltage) and do all of the cold-junciton compensation, amplification, A to D conversion, etc. They output the temperature in C as a 10 or 12-bit number over a SPI connection.

If you want to tinker a little, I would definitely suggest giving them a shot. It looks like one of the authors in that thread also has breakout boards available on his website for these chips.

 

Got my DS18S20s in. Hooked them up, got the Arduino to find and read from two NICs on one data line, which is pretty sweet. I also wrote a script in Processing that could read the data streaming off the Arduino and output it to the sketch.

I also tested having a LED turn on when the thermometer hit a certain temperature, worked like a charm. Now I need to find a relay that the Arduino's 5v supply can trigger and control 240V AC. Anyone have any suggestions?

 

No, those are type K thermocouples I was using for testing. The easy thing to do would be to drive a NPN transistor with the Arduino and then use the transistor to do low side switch on the SSR or a DC coil mechanical relay. If you do use a mechanical relay you will need to put a blocking diode across the coil to prevent the inductive kick from cooking the transistor and other components when the relay switches.

 

Back to the topic, I finally have had some time to sit down and work out the issues in my RTD circuit. I am happy to say that it is now pretty precise and tuned to work in the 0-100C range we need. I'll be ordering the final revision of copper tomorrow.

 

I'm using this DS18B20 probe in my fermentation controller.

Also using this thermowell and this SSR (10ma, driven directly by the Arduino).

 

How about a build thread? I've seen you post it in a couple of threads, and would be interested to see how you put it together. I'd also like to compare the code to Mine.

 

Here is mine currently. I am just waiting for stand-offs to mount the LCD. Oh yeah, and the refrigerator. I ordered it from Home Everything nearly a month ago. I called about the delay and was told they, 'wait until they have a full truck so they can give free shipping.'

I used an ESawdust Arduino crib case and cut a hole for the LCD.

I chose the FreeTronics TwentyTen Arduino since I needed so few components I didn't want to add a shield. It has its own, small prototyping area.

The only components on the Arduino are 4 connectors: LCD, temp sensor, SSR signal and 10k pot (for setting the desired temp) and a resistor for the DS18B20.

I jammed a blue LED under the RJ11 connector in the AC box so it will glow when the fridge is on. Weee.

Here is the schematic. I couldn't find an Eagle library that had a working DS18B20 so I subbed a transistor.

Edit: When I followed your link it displayed hardware and I forgot you wanted to compare code

 

Image of final product, for posterity


I used a 20x32 sheet of acrylic glass from Home Depot painted black on the back. It was about $12. Drilled a hole in the back at the very top, in the center for the temp probe wire.

 

Bumping... CodeRage... Did you ever finish this? Got a writeup? Thanks.

-Eric

 

Just bought an Uno with a couple Dallas sensors. I'm looking to replace 10 PIDs for work and eventually get it to work for my new brew rig too.