[max] can I use some random temperature sensor with max thermostats?

Hi there,

I am trying to find documentation if I can use any other wallthermometer than the original Max! ones. I’d like to feed the measured temperature to Max! Thermostat+s and Max! Thermostats. I think I’d want to use those Xiaomi ones for 10 bucks, with temperature / humidity / pressure sensors, because we have issues with humidity anyway (old building), and I’d like to setup a warning anyway when humidity reaches too high levels.

Is the max! binding capable of supplying temperature from a third party thermometer to the max! thermostats?


Edit: A solution might be to enable periodic measured temperature updates for the thermostats, and continually adjust the temperature offset with that measured from the wall with a 3rd party device.

Of course you can. That’s where openHAB is very strong. You can integrate almost any technology.
When an item is linked to a binding, it doesn’t matter what the underlying technology is.
The items in the rules can be dealt with in the same way and openHAB bindings will take care of the rest.

So, the actual_temp property is writable, and it works well? Because with FHEM it is only possible in CUL mode, not with a Max! Cube.

I had the same idea with Max thermostats and Xiaomi temperature sensors.

I agree that you can manually change the value of actual_temp in openHAB, but I believe that the Max thermostat doesn’t care about that so it’s not writable in the memory of the actual thermostat. What I mean is that only openHAB will see the newly set value. As far as I’m concerned the thermostat itself is controlling its valve and not the openHAB Max binding.
So even if openHAB sees that the desired temperature is set to 20°C, the valves are open to 100% and the manually written actual_temp is 15°C it won’t close the valve unless it actually measures a temperature of less than 20°C
Correct me if I’m wrong, but I think you need the CUL binding to achieve that the actual_temp is being written to the thermostat.

But what you can do is to control the valves by using rules, for example: if temperature_xiaomi < maxSetTemperature then maxSetValve 100%

So you need to analyze which valve setting is required for which temperature difference and so on. Maybe it’s not as complicated as I think it is.
What I actually did is to use the Xiaomi temperature sensor and adjust the offset of the Max thermostats. No it’s not great and it’s not satisfying, but it was the easiest way for me until somebody comes up with a better idea :wink: