Do I have to build my own touchscreen thermostat?

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Nah, just get one that can integrate with Home Assistant.

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Nah, protect your privacy and build your own. You just need an esp board, a 4x relay board, and a thermometer sensor.

Ephera

I mean, as far as my mum is concerned, even setting up the TV channels correctly is "programming"...

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Thermostats are Barney basic in function, touch the red to the hot to call heat, red to yellow for cool, and red to green for the fan, then open the circuit when the temp is where you want it. Kinda sounds like a fun project.

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I had no idea it was that simple! How do you control heat pumps? I know they have a setting where if outside is too cold it runs backup electric or gas.

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Is that the same for the ones with the C wire or any of the other crazy wires?

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I have a heat pump as well as a furnace (for auxiliary heating). The thermostat frustrates the hell out of me! For one thing it loses its date and time (yes it has a full calendar date and time as well as time zone) if there’s even a single second power outage. How hard would it have been to put a CR2032 battery and a diode in there just to run the clock when the power fails?

For another thing, the thermostat itself runs extremely hot. Just putting my hand on it, it feels super warm to the touch. The LCD touchscreen on the other hand has molasses-slow response time. It’s almost impossible to set the temperature on the first try without overshooting by 2 degrees.

Lastly, it is designed to be able to run both the heat pump and the furnace when heating load exceeds the capacity of the heat pump. The thermostat also has a sophisticated time of day temperature set point schedule system (with separate schedules for every day of the week). However, the damn thing does not correctly reconcile these two facts!

I have the system set for cooler temperatures at night and warmer temperatures in the day. When the morning arrives and the schedule hits the higher day time set point, the thermostat suddenly sees a multiple degree deficit vs the set point and then calls for emergency furnace heating because it thinks the heat pump is failing to meet heating demand!

This is so maddening and stupid! Why can’t I have the temperature set point just continuously and cyclically vary throughout the day and night like a sine wave? No, the dumb thing runs the heating and cooling schedule as a square wave and therefore runs the furnace every single morning in order to slam the temperature up by a few degrees to the day time set point instead of gradually ramping it up over several hours with the heat pump…

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They have their own microcontrollers usually to manage that stuff, including defrosting

AwkwardLookMonkeyPuppet

Honestly, that's how competent programmers look at just about everything these days, especially junky-ass websites that probably couldn't violate more best practices if they tried.

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If its a cheap crappy one, the compressor is on/off depending on temperature. Decent ones will have a VFD to manage the load of the compressor so it doesn't have to turn on/off all the time but just regulates the compressor load to match heating/cooling requirement. Both have their own controls, and you generally shouldn't mess with them.

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Heat pumps are not simple at all. They are extremely efficient but can’t produce a large temperature gradient so they need to run very long cycles (potentially remaining on 24 hours straight). Modern cold weather air source heat pumps also tend to have variable output (variable speed compressor, variable speed fan). This demands a more complicated thermostat that adjusts the heat pump up and down, possibly with PWM.

And then there’s the emergency/auxiliary heating from the furnace. The thermostat needs to have some intelligent logic to decide when the heating demand exceeds the capacity of the heat pump and call for the furnace.

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If we're on this subject, do you happen to know any active esp Lemmy communities?

thanks and merry christmas

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Heat pumps are an entirely different story, and I don't have too much experience with them, most of the splits I've seen come with their own remote controls. I was talking on more traditional wall heaters, central air/furnace/forced air, etc.

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Most programmers (those doing fancy GUIs and C# programming on a PC) would be seriously out of their league if they ever actually tried to program such a thermostat. Or any other embedded system. You really need a special skillset and hardware knowledge to even get a simple embedded system running. This is what my trainee just learned the hard way in the last weeks...

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Yes, the C/blue wire is common, basically a neutral for the 24v system and necessary for more digital thermostats to keep the thermostat powered (some can work without the c wire, but it depends on the unit feeding power). The old mechanical ones work on the tilting mercury thing or copper coil for temp sensing, and only require the red wire to touch their respective wires to call whatever function, but the digital ones do the same thing on a switching level. I know there are additional wire sometimes for multistage heat and zoning, but as far as I know it's the same principle. I'll be honest I'm an electrician by trade and not an HVAC guy, and I know some of the more intricate systems can deviate from this, but your average residential system should be similar or damn near the same as my original comment (granted my experience is in Southern CA, so there are possibly regional differences with oil furnaces, radiator systems, etc).

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Everything is laugh and giggles until the thermostat is turing complete.

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"Smartknob View"

Sabata

Tape a raspberry pi to the wall with some relays and a temperature sensor dangling and call it a day. Anything else is spying on you.

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Except thermostats. You literally could do it with a Raspberry Pi, some 24V relays and a temperature sensors. Thermostats are not that hard.