Do I have to build my own touchscreen thermostat?

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A smart thermostat is the only smart device I own (ecobee). I figure it actually is better than something I could design in a week so it seemed worth it. Do you know of an actually competitive open hardware/open source solution?

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Smart thermostats do way more than just set the temperature: that's table stakes. Off the top of my head the ecobee will:

Set the temperature also taking the room's humidity into account
Communicate with sensors throughout your house
Can change things via the Internet in case you accidentally forget to set it to a better temperature when you'll be gone for a few days
Tweak your schedule based on demand

I'm probably missing things, but they're actually pretty useful, and I'm someone who thinks most IoT is shit.

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Well that's not quite true.

I have some z-wave thermostats, which I know do not talk to the Internet, just a local system with a zwave dongle.

For a relative, recently set up a similar setup, but with a homekit thermostat. Similar deal, though it really really wanted to connect to a cloud server and you kind of had to trick it to a non apple homekit setup. The follow on model from that brand did drop homekit support, presumably because they wanted to force their cloud servers, which became required for any advanced functionally.

There are ways to get automation friendly devices without a cloud connected requirement, though admittedly you have to be paying pretty close attention. Generally offerings for business are more likely to be locally workable, but that's hardly a given either

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As the other poster said, both Zigbee and Zwave devices do not talk to the Internet. They can't even connect to your Wi-Fi anyway. They need to connect to a device that acts as a router but specifically for Zigbee or Zwave, usually called a Hub or Coordinator.

There's many different hubs around. Many commercial ones do indeed connect directly to the WiFi and therefore internet. But nothing is stopping you from buying a USB Dongle Hub with open source firmware and plugging it into a Raspberry Pi, if you want to eliminate the potential spying.

The Zigbee and Zwave networks inherently cannot communicate with the Internet. So the only risk of spying is if you installed something in the Raspberry that spies on you.

Both Philips Hue and IKEA Trådfri and many other vendors simply use Zigbee, which means you can bring your own Hub and completely eliminate the risk of spying.

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Which are all things you can easily do with an RPi and some simple python. My response was to OP stating that embedded systems are hard.

If you’re using a specific embedded system and want to make it pretty, sure that could pose some issues, but if you want to make something functional that matches what a smart thermostat can do, there’s not much behind it.

Sabata

Do you trust every device you buy without question?

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Noting ESP specific to my knowledge, but there is a home assistant community.

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my high efficiency HVAC unit would like a word with you.

what you're saying is basically you can replace anything with a RPI. yes, in theory, you are correct. but, unfortunately for you, there are nuances that you didn't take into account. such as, startup/shutdown procedures, cool down cycles, heat pumps, dual compression ac units, etc.

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Nope, but I trust the ones that lack the hardware for dialing home.

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Alright I'll check it out. Tnx:)

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All of that is handled by the HVAC (if there's anything to handle) and not the thermostat

Thermostats can be (and most often are) a bimetallic strip that bends one way as it cools and bends the other way as it warms, and that flips some switches that you set for temperature ranges which then demands cool or hot from your hvac

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Raspi is overkill. Mine runs off an esp32 using code I wrote in Arduino. The web interface takes up more space than the code.
Only reason it's an esp32 instead of an Atmega 328p is the wifi support

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Which are all things you can easily do with an RPi and some simple python.

Just like anyone can “easily” rebuild their transmission or patch a piece of leaky copper pipe or bake an apple pie from scratch or hit a bullese from 50 yards out.

What’s easy for you isn’t easy for everyone.

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And deal with breaking updates happening on HA and the thermostat software itself while simultaneously maintaining api keys and policy changes every 2-6 months.

Its hard work

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This is the way.

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Programmers love to oversimplify things, like "do easily with an RPi and some simple Python" is kinda meaningless. For one, UI/UX is actually hugely important for a consumer device and definitely nontrivial, but on top of that, there is way more that goes into creating custom hardware than a bill of materials and choosing a programming language...

A thermostat is controlling a hugely expensive device that runs on a highly flammable gas that costs me real money to use. I want 0 bugs. I also want 100% uptime. I also want my partner to be able to control the temperature in the house. These devices are actually not simple at all and I assume that's the reason there isn't a good open source/open hardware solution.

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I SWEAR it's impossible to make fun of the selfhosting / hacking communities. I made a joke once that they should hack a toothbrush then I found they already did

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That is the simplest possible thermostat and works great for setting a temperature, but that's not the ideal thermostat. The temperature your house "feels like" also depends on humidity. You may also care about the temperature more in a spot further from the thermostat and getting accurate measurements in that location can save you money and waste less gas. There is also the decision of how long you should run a furnace and, in the case of multiple stages, which stage you should run, although some furnaces control the stages themselves. Then there is air flow. Controlling the fan separately is useful if the house doesn't evenly heat. Sometimes you can just have the fan work and use the actual furnace less, saving gas again.

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From my understanding, those days are in the past. I can't speak to that from experience because I only recently got into HA.

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I could see that, but you have to remember that the average consumer doesn't have an automation hub or get deep into the automation sphere, and as such many of these products are designed to be standalone devices that can be controlled from a phone. Often enough they can be the only 'smart' device in a home.

That all said, a dumb thermostat like your suggesting would still require a small CPU, ram, embedded OS, and network stack/hardware to operate and communicate, so I don't know how far the savings would go. I can't imagine the processing power on something like a nest is that powerful as it is.