Wednesday, November 16, 2011

OpenTherm interface ready!

If you have been following this, you know I have been busy getting a JeeNode (arduino compatible) to talk to the boiler suing the OpenTherm protocol.

I am glad to report that the circuit, which you can find here works fine, and the code available in github, is also functional! Sometimes it hangs when first connecting to the boiler, but a reset of the JeeNode solves the problem. Will try to investigate (I have some ideas)

Today I was busy finalising some details, and implementing communication with the server to get the set temperature. All is ready, except one little linking piece of software: the listener that listens to messages coming from the JeeLink has to now accept messages via the serial, which are sent by the module that calculates the set temperature. Maybe for the next post I make a diagram of the software layers involved.

Anyway, here is a picture of the little thing!

The little icons represent: radio link, OpenTherm link, flame, Central Heating, and Hot Water. T1 is the outgoing temperature, T2 is the return temperature, Ts is the set temperature, under the reported set temperature, and to the right of the Ts the received from the radio (for debug...will delete that). The 5 is just a number that changes once a cycle, and serves as an indication that the whole thing is still working.

You can see the yellow antenna, and the home made PCB, the one with the blue connector block.

I will get a PCB done externally, to learn how to do that (although Joao is taking care of that), and then get the whole thing in a nice enclosure.

The next hardware version will be to get the thing powered from the OpenTherm bus, which should be possible, as it provides 5mA for the master to operate. That should be enough, given that the radio only transmits once a minute!


amelia said...

A very simple but a very good work.
Do you know the protocol "BSB Boiler System Bus" from Siemens ?

Alex said...


I didn't know that protocol. I will read about it as soon as I have some time!

J Silva said...

You're a real artist! Just love the icons!
Well done!

Alex said...

Thanks! we had not yet discussed these had we?