Decoded - EvoHome API access to control remotely.

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  • paulockenden
    Automated Home Legend
    • Apr 2015
    • 1719

    Remember that percentage open isn't quite the same as calling for heat.

    But also, HR92s don't just have an on/off heat demand - they can call for a percentage, as I understand it. So that's two percentages.

    Comment

    • jzwack-honeywell
      Automated Home Jr Member
      • Jan 2016
      • 36

      Originally posted by paulockenden View Post
      Remember that percentage open isn't quite the same as calling for heat.

      But also, HR92s don't just have an on/off heat demand - they can call for a percentage, as I understand it. So that's two percentages.
      That's true, thanks for correcting my language.

      But to answer the question, it's usually a firmware function that reports that data up to our servers. Without going to bug the engineers (who are not working at the moment), I would assume that's why you don't see it now. Reporting that data via the API is different than the actual functional operation of the device.
      developer.honeywell.com | I work for Honeywell. API Evangelist. Views are my own.

      Comment

      • DBMandrake
        Automated Home Legend
        • Sep 2014
        • 2361

        Originally posted by paulockenden View Post
        Remember that percentage open isn't quite the same as calling for heat.

        But also, HR92s don't just have an on/off heat demand - they can call for a percentage, as I understand it. So that's two percentages.
        Yes, the HR92 as well as having a continuously variable valve opening (Reported by Valve Position option 10 on the HR92 itself) also calls for heat on a percentage scale with 0% meaning no demand for heat (boiler off if no other zones have demands) and 100% meaning run the boiler continuously. (Which occurs if the zone is about 1.5 degrees or more below the set point)

        When in the proportional band they call for an intermediate value such as 50% that varies to help regulate the temperature. The interesting thing is that the HR92's don't talk directly to the Boiler Relay/OpenTherm bridge, they are only bound to the Evotouch controller, so they communicate their individual heat demands to the controller which then combines their individual demands using some algorithm and sends the aggregate heat demand to the Boiler Relay/OpenTherm bridge.

        So the information about which Zones are calling for heat and what percentage is available to the software running inside the Evotouch controller, even though it chooses not to expose that information via the API, or through the user interface. (It should be possible to obtain this information by snooping on the wireless communcations between the HR92's/Zone Thermostats and controller, and controller and Boiler Relay/OpenTherm bridge with an HCI 80 though)

        Making available the information of which zones are calling for heat via the API or user interface sure would make diagnosing unexpected boiler operation much easier...
        Last edited by DBMandrake; 20 January 2016, 09:58 PM.

        Comment

        • paulockenden
          Automated Home Legend
          • Apr 2015
          • 1719

          I once discussed with a senior chap at Evohome [waves in case he's reading this] that it would be good to have two versions of the controller. A 'normal' one for average users and an 'enthusiast' version for tinkerers like us. The more I read the forums the more I'm convinced that would be a sensible move. We're all asking for things that could potentially introduce more risk of failure into the product, which would be unacceptable to the wider audience, but which those who wish to play might accept.

          The idea isn't unprecedented - some broadband router manufacturers, for example, have 'official' firmware, and also older versions open sourced which people can go away and play with.

          Comment

          • Caesium
            Automated Home Jr Member
            • Oct 2015
            • 13

            Originally posted by DBMandrake View Post
            It should be possible to obtain this information by snooping on the wireless communcations between the HR92's/Zone Thermostats and controller, and controller and Boiler Relay/OpenTherm bridge with an HCI 80 though
            Don't suppose anyone is in a position to check this? I'll buy one if its the case..

            Comment

            • SteveP
              Automated Home Guru
              • Dec 2012
              • 190

              What I'm waiting for is someone to release an app with graphs and 24 hour history of each zone for which I would pay. I would prefer it as a local install rather than a web service just cos I have a thing about security and the cloud. I have a programming background but now focus on data architecture so whilst would love such an app I don't have the time to write one myself and am a bit rusty on languages (anyone remember COBOL!!). Must be a market out there for such as product - maybe the group here could collectively form a business and market one. I'm up for purchasing one at the right price
              Last edited by SteveP; 21 January 2016, 05:14 PM.

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              • paulockenden
                Automated Home Legend
                • Apr 2015
                • 1719

                Would you rely on Evohome's own temp sensors, or would you want properly external sensors?

                I'm tending towards the latter, if only to compare with the former.

                P.

                Comment

                • Rozza
                  Automated Home Lurker
                  • Dec 2015
                  • 7

                  I have created an app and a windows service to log the evohome data along with the weather data from wunderground, currently logging to a SQL server db but this could be changed to something else without too much effort, API code is based on what someone posted in this thread

                  example of a day for a zone
                  client.jpg

                  an example of if you hover over an entry, shows the weather data
                  weather.jpg

                  Comment

                  • DBMandrake
                    Automated Home Legend
                    • Sep 2014
                    • 2361

                    Originally posted by paulockenden View Post
                    Would you rely on Evohome's own temp sensors, or would you want properly external sensors?

                    I'm tending towards the latter, if only to compare with the former.

                    P.
                    If you're going to go to the trouble of putting remote temperature sensors in each room to get a more accurate reading, why not just use a remote DTS92 so that the Evohome itself is also measuring the temperature more accurately, and thus controlling the room more accurately, instead of just measuring it accurately and finding that it was not controlling it as well as it should due to measuring at the radiator.

                    You could use one reference thermometer to calibrate each DTS92. Of course there is the issue of the +/- 0.5 degree bias towards the set point, however does anyone know whether this bias also exists in raw data as monitored over the air by an HCI 80 ? I suspect not, and I'm sure I read that the raw data reads down to 0.1 deg c increments even though the current UI and Web API only read down to 0.5 degrees, with weird rounding behaviour... If it does indeed read to a resolution of 0.1 deg c and without the set point bias, it could be very workable to collect data in this way.

                    Comment

                    • paulockenden
                      Automated Home Legend
                      • Apr 2015
                      • 1719

                      Originally posted by DBMandrake View Post
                      If you're going to go to the trouble of putting remote temperature sensors in each room to get a more accurate reading, why not just use a remote DTS92
                      Because of the issues that you describe - 0.5 degree resolution, plus a bias towards the setpoint.

                      Also, a load of Z-wave (or whatever) temp sensors will be cheaper than DTS92s.

                      I think for a lot of people, room or rad stat reported temps will be fine. But I know there are also people in this very forum who don't trust them.

                      P.

                      Comment

                      • SteveP
                        Automated Home Guru
                        • Dec 2012
                        • 190

                        Untitled.jpgUntitled2.jpg
                        My son created the attached but didn't finish it before he "got distracted". It worked well providing a 24 hour rolling view of each zone showing external temp, room temp and set point. Sort of thing I am looking for and willing to pay for. It keeps crashing though and my son has too many other things to do to sort out.! The pop up allows you to hover over any point on the graph and it will show the 3 temps.

                        Comment

                        • MrB
                          Automated Home Sr Member
                          • Oct 2015
                          • 80

                          I'm another who has created a Windows Service to capture all "realtime" data to a SQL database, and the new URLs are definitately quicker. Once in the DB you can do whatever you want with it visually and programatically.

                          I also add my vote to get the HR92's heat request data via the Device's JSON data - it is the real missing bit of data to track exactly what the system is doing and why. Just always having "OFF" reported is a tad pointless.

                          Comment

                          • benc
                            Automated Home Lurker
                            • Sep 2015
                            • 7

                            I'd love to have something along the lines discussed above. I'm not too fussed about where the temperature is read from. I'd be happy to pay for this if it wasn't mega-expensive.

                            Comment

                            • nico
                              Automated Home Jr Member
                              • Oct 2015
                              • 14

                              SteveP the interface of your son is good, if you share it maybe I can find some time to work on it.
                              You can check my work in the attached picture, data logging (measured and setpoint), 12h/24h/48h/week/month view, single zone temperature hideable from the graph, external temp from wheatherunderground. We could merge the works. My code is a little bit rough and customized form me, I should work on it to generalize as much as possible, but I don't have much time.
                              Originally posted by SteveP View Post
                              [ATTACH=CONFIG]658[/ATTACH][ATTACH=CONFIG]659[/ATTACH]
                              My son created the attached but didn't finish it before he "got distracted". It worked well providing a 24 hour rolling view of each zone showing external temp, room temp and set point. Sort of thing I am looking for and willing to pay for. It keeps crashing though and my son has too many other things to do to sort out.! The pop up allows you to hover over any point on the graph and it will show the 3 temps.
                              Attached Files

                              Comment

                              • Krejt
                                Automated Home Jr Member
                                • Jan 2016
                                • 21

                                Nice work @Rozza, @Nico, @SteveP's son! Can't we start a dedicated thread for projects using the API to store data and/or display graphical info? I'd love to know what tools you use, what platform etc, and what the result could be. And if you provided the code you use we could all benefit and help eachother?
                                Evohomeclient temperatures on ThingSpeak: https://thingspeak.com/channels/79213

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