RF to Zigbee gateway

The last piece of missing hardware is finished. The picture below shows the 2nd RF to Zigbee gateway I had to make to be able to receive all the Hydronic balancing sensors I made earlier this week. One of those sensors just couldn’t make it through 3 walls all day long, so I created  a temporary solution on a breadboard to solve this.

A very simple yet effective way (for me) to get the sensor data where I want it (in my Domotica system) with minimal effort.

The JeeNode acts as a RF receiver and just echoes everything with a valid CRC to the Digi XBee; from there it eventually arrives at my Zigbee Coordinator with which I can communicate over TCP/IP.

The JeeNode runs a slightly modified version of the RF12Demo sketch made by Jean-Claude Wippler. I used the NewSoftSerial library to create an additional Serial port, and added a few print statements for the XBee port, right there where the RF12Demo Serial.println()’s the received RF data to the Serial port. Compile, Upload, setting the RF band,  group- and node ID and I’m done!

This JeeNode is powered by a 5V USB adapter and the XBee gets its power from the 3.3V JeeNode ports. The XBee uses a Zigbee End Device AT firmware (2864) with the Sleep Mode set to Pin Hibernate. But because pin 9 is wired to GND, this means that the XBee is permanently on.  Only 3 wires are needed to connect the XBee to the JeeNode: 3.3V, GND and a JeeNode digital pin to the XBee DOUT.

That’s it – moving on with where this all started with: understanding the flow of  heating energy in our house!

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10 Responses to RF to Zigbee gateway

  1. Petr says:

    I really appreciate your effort. I am thinking about Max! Cube as well.

    I am in the stage ONE. I mean we are installing pipes and radiators etcetera…
    I am studying possible solutions.
    AFIK it looks the more appropritat is the “fhem”. see: http://fhem.de/fhem.html

    By the way, I would like to know what do you mean by the terms “the Hydronic balancing sensors” and “Hydronic balancing”.
    In my point of view: if you are not able to measure the hydronic pressure or hydronic fluid flow, it is, IMHO, not possible to talk about “Hydronic balancing” or about “Hydronic sensors” at all.

    I like the idea to know the in/out temperatures on radiators. I think it is the best way to know the I/O temperatures during the day.

    But I really do not understand, how it is connected with the hydronic flow or with the hydronic balancing.

    An other question: do you know some other people interested about decoding the Max! Cube wireless protocol?





    • From what I have learned so far (it’s all still very new to me), there are several ways to apply hydronic balancing. Especially in an existing system it’s not that easy to enable flow measurements there where needed; another way to “do” hydronic balancing seems to be the so-called “Temperature method”. Basically, this means measuring the delta-T on all heat exchangers in a stationary condition of the central heating (=burning @ 100%) and changing those delta-T’s to the values needed. This method is often applied when the more accurate and preferred method of calculations based on the characteristics of all the central heating elements (central heating, piping, radiators, isolation, room volumes, etc.) cannot be used. So, IMHO, hydronic balancing can be done without flow measurements, although the margin of error will probably be larger. (10 vs. 20-30%)

      No, I don’t know anyone working on or interested in decoding the MAX! Cube wireless protocol.

      Question for you: why would you want to decode the MAX! Cube wireless protocol. For me, the Cube is a tool to completely open a valve, completely close a valve or set a temperature I want. What will the wireless protocol add to this?

  2. Jeroen says:

    Hi Robert,

    Can you share the code/sketch you are using an the hydronic balancing

    Thnx and kind regards

  3. Jeroen says:

    I would like to take a peek at the code for both setups.
    Are you still going to make the Opentherm gateway ?

    Have you look at the option that Jaga provide called Dynamic Boost Effect
    low temperature boosting ..


  4. Catalin says:

    I’ve followed you work in decoding and using MAX in you home automation system and I wuold be interested in buying one.
    However, is there any way to control the boiler only by the Max cube ? How does the boiler start when there is heat demand from a room where there is no thermostat? For ELV/Conrand there is FHT 8w relay that “starts” the bolier when needed. Is here something similar?

    Thank you.

  5. Hary says:

    You’re right, I have no means to measure the water flow. What I do have, is teamerpture sensors in every room and (since a few days) I can measure the difference in flow- and return teamerptures of all the radiators. I like to think (until proven otherwise) that this will be enough for me to apply changes to the central heating system and create a more balanced energy circuit.After adding 2 radiators downstairs (in the office downstairs, which was built in 2001) and the floor heating in 2009, too much energy is flowing to the rooms downstairs. The result is that the rooms upstairs don’t get enough energy and barely heat up anymore. This can’t be fixed by automatically throttling valves (IMO), cause this would mean you’d have a central heating that will first primarily warm up the rooms downstairs to the desired teamerpture, and only after downstairs has been warmed up enough the second floor will get some more energy (cause those valves downstairs will close and reroute the heat to the 2nd floor).So the answer to your first question is yes. And no, there are no other actuators (I want to use or) that you are missing. Although I could switch off the floor heating pump easily. But I don’t want to do that.Maybe the above also answers your 3rd question?

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