Project CANxtra HTD (Heating Tuning Device)

Hi all,

First of all, again thanks to the GHI team for the gift I (and some of us) received. In my case, the gift was a CANxtra. This is an awesome device with a great little OLED display in a nice case.

I couldnt put this in my drawer so I started to thinker for what I could possibly use this. And then I came up with the following: A Heating tuning device. Yeah, I hear ya, what the heck is that.
If you have central heating, it is important for both performance and optimized gas consumption that each radiator is regulated in a specific way. The outlet temperature of the radiator should be 20°C less than the inlet temperature. You do this by turning the valve of the radiator left or right.

And here is where the CANxtra comes into play. I bought 2 analog LM35DZ temperature sensors to measure both inlet and outlet temperature. Why not OneWire sensors? Simply because they dont react fast enough. So what do we have to show on the display? The inlet temperature, the outlet temperature and of course the temperature difference. Does it end here? No, tuning all the radiators takes time, and Im not planning to keep an eye on the CANxtra display 24 hours a day. So logging is the answer. Pop in a micro SD card and log every x minutes (5 in my case, that draws some nice graphs). But wait, wouldnt it be cool if I could monitor this remotely from my PC? Running all the time around in the house isnt the solution, so a webserver idea was born. Thanks to Wouter Huysentruit I added the webserver to the CANxtra. All the files including html, javascript are hosted on the SD card. Theres a static html page that contains the layout of the page, and a virtual file that spits out JSON data (thanks again Wouter Huysentruit) to update in an AJAX style the values on the html page.

This gives me the possibility to fine tune each radiator, monitor remotely and log the temperatures over a longer period.

Credits go to Wouter Huysentruit for his excelent Webserver and JSON classes, and to GHI for their unbeatable support and great gifts.

Hoping this post was usefull to someone.


PS. The images were not taken at the same time, hence the different values on the CANxtra and the webpage.

Very cool, bit no video :frowning:

I’ll shoot a video when I’m actually tuning a radiator :wink:

@ EricSan500 - Nice! You’ve confirmed my thought that the canxtra would be a great home automation brain.

@ Gus - Since you handed out a bunch of these, I think you’ll see a resurgence in their popularity! I’m about to start another thread with some questions about a robot arm video I found…

Cool! Now I can finally see it! Nice project!
I just LOVE canxtra’s display :-[

Nice job! Kicking myself for not getting a CANxtra when they were $49… :’(

I did recommend it :slight_smile: But hey you are special! If you really want one for the sale price then send me an email gusi@ ghielec…

Yea, I know… But, I’d already spent about $600 the past couple months getting the quadcopter project started. I have to restrain myself somewhere… :wink:

Nice work Eric!

So fill me in on your sensor harness. Why do you need power from the USB host (i’m guessing that’s what it’s for)? Also, where’s the code hiding?

Because there is no power on the DB25 connector, and the temp sensors needed 5V to work.

Behind the LCD (LOL)

Ha de haha… no really, did you share the code? or do I just need more coffee?

There’s no rocket science involved, but if you want a copy, i’m willing to send you the code by email. :wink:

HI Eric:
Do you have website or any paper tell detail about your project?