Turning a dumb AC unit smart (without losing my security deposit)

It always kind of blows my mind that I keep seeing "smart TVs" which have a bunch of integration options for high-end AV installations (rich people's houses, etc.) but no API that you can integrate with to just handle toggling channels/inputs/power states/volumes.

(I did get my last Sony Bravia integrated with Homekit so that I could control inputs, volume, etc. via the Home app, but that's not really what I'm looking for).

Give me an HTTPS API, require me to authenticate devices on the TV itself before it accepts their commands, and just let me do whatever. Default it to off and make it a hidden setting, but yeah just let me do the thing without having to pay tens of thousands of dollars for some professional installation to integrate with hardware I don't have and can't afford.

Exactly.

I don't want a "smart" washer / dryer / fridge / toaster. I want a standard interface I can build my own system around, or use someone else's that they've already built.

>HVAC equipment does this with standardized thermostat terminals.

yes, they standardize thermostat terminals, but they should allow additional inputs such as a measure of radiant heat entering through the boundary surfaces. I have to change my thermostat far more because it's a sunny day than I need to because of different outdoor temperatures. Bear in mind, I shouldn't have to change my thermostat at all† (except perhaps between summer and winter)

† perhaps my biggest pet peeve, and I have many, is that 99% of the population—including engineers from top universities—believe that if you feel warm you should imediately max-out your A/C thermostat, and when you get cold you should shut it off. It's a thermostat, its job is to turn on-and-off to maintain a temperature. I never touch the one in my car and it works great. (as mentioned, I need to change the house thermostat, see solar radiance‡ above)

‡ I once had the pleasure to work with a great mechanical engineer, he designed climate systems for art museums and other public and billionaire buildings, and I described my radiant heat problem and he said "that would be super advanced, I've never heard of any systems that do that."⹋

⹋ another one of my pet peeves is footnotes. In general, they require a massive context shift, as if it's not a problem to keep your place while you look in another place. But notice how I've threaded mine so they do not require congnitive leaps.

>HVAC equipment does this with standardized thermostat terminals.

The industry hates this and wants it gone because they want you locked into buying the rest of the stack from them and they want you shelling out $$$ for emergency repairs rather than jumpering it when it fails at a bad time.

What I want instead is for devices to ship a (tiny) HTML/JS control panel (or its hash if ROM space is limited), using some specialized interface to make requests over BLE or a relay chosen by the user.

The reason we need an app in the first place is 1) customizability, 2) ability to access the device even when out of WiFi range, even when behind carrier-grade NAT and/or a restrictive firewall. A design where the device hosts a simple "server" that makes an outbound connection to a proxy of the user's choosing, likely provided by their smartphone vendor, to receive requests would solve both problems.

When I had a kitchen fire, I told my electrician "no smart stuff" and he was happy to go along. (I had very little previously.) He did simplify and updated my electrical panel and switches which sort of accreted over time.

Nowadays it's surprisingly easy to vibecode replacements to some shitty OEM apps (and fix bugs while you're at it). I've had pretty good luck with BT devices, even ones that dont use standard GATTs

Many smart meters have an LED that blinks every time you consume a watt-hour.

This is what drives me to sometimes DIY devices instead of buying them. There is so much crap on the market and it gets increasingly hard to tell where the catch is. Does it only work with the manufacturers weird cloud? Which feature(s) do work without? What settings are even possible?

Really simple appliances can be very hard to find, e.g. a desk fan that can be set to spin very slow. Most fans have 3 or 5 speed settings and the lowest is already tenfold too high for my taste. Solution? Get the dumbest fan you can find and speed control the motor yourself.

PTACs suck. Well-maintained, newer models suck less, but they still suck. Unless well-insulated, the sleeves leak air (and humidity). And there's a duopoly between Ice Air and Islandaire, so they get to charge more for maintenance. They benefit from the trend of maintenance for older models being a yearly chore also.

From what I understand, PTACs started as a convenient way to retrofit apartments with air conditioning. You don't need ductwork, which I believe is more expensive in the concrete buildings around here. Also, I think you need protected refrigerant sleeves to meet code here, but only if the sleeves go from one floor to another (someone just told me this fact today, and i haven't verified this).

BTW that PTAC's thermostat dial in the link doesn't have numbers around the dial, which I think is honest. No A/C unit I've ever owned has managed to have a thermostat that read the temperature I was feeling consistently. It makes me think the apartment was built before the late 2010s though -- still feels new but a generation ago in HVAC terms. Mini-splits seem to have arrived, even for <1M condos. Talking to the mini-split contractors I had over recently for a squeaky noise, I got the feeling that business was booming. They had every day in the summer booked months in advance.

Garbage disposals were at one time illegal, and despite the passage of 30 years there’s still concern in existing buildings that the plumbing can’t handle it (which is probably unfounded).

As someone else mentioned, a software-oriented solution is likely to introduce more failure modes because of the number of dependencies, updates etc.

This, I'm very surprised they didn't go with it.

> If all you need to do is replace a potentiometer with electronic control, it may be possible to do that with a vactrol. It's more invasive perhaps, but then we're not dealing with anything mechanical.

This is what I was wondering about as well.

The knobs on the unit are probably potentiometers, so it ought to be possible to replace them with a digital device of some kind, and avoid the mechanical coupling altogether.

I imagine that the author did consider this possibility, but decided that disassembling the control panel in order to replace or byypass them was just too difficult and dangerous, especially since everything is at AC line voltage as he notes in the write-up. The modern smart thermostats that I've looked inside have a clean separate between the low-voltage digital side, and the AC-line-voltage power control side… but evidently these older purely-analog devices didn't.

ESP home is so powerful like this. And is great to build components for (although I find this part a little complex, lots of Claude help…).

I’ve got a vibe coded “Nuaire Fan” controller to talk UART to my whole home ventilation and present it as a HA controllable fan.

For the purpose of cooling, just setting the thermostat to its hottest setting would be in effect "off" just about all of the time. Depending on the design/temperature range of the thermostat, this isn't 100% though.

If you want to be able to do both heating and cooling, it'd get a bit complicated since the above would be inverted for heating.

> binary on/off

On older ones, but newer ones can modulate blower speed, compressor speed, and refrigerant flow. Don't think I've seen an air-con without blower-speed as part of the cooling apparatus for a long while.

That's what I did. Just an esp32 relay board with a tiny screen and a knob. Then I put more esp32 sensors in each room to get individual temps, with HA logic to select which room the thermostat pays attention to. If HA dies for some reason it falls back to a local control and I'm back to the same situation as before, a thermostat that only pays attention to the temperature in the hallway it's installed in. All the boards were flashed with ESPHome.

It does feel hella jank, but it's pretty obvious from the tone of the text that the author is fully aware of that. He went through every available option in order from reasonable to jank and this is the first one that worked.

There's nothing wrong with jank as long as it's not going to burn your house down the way some of his other rejected ideas would have.

I think you could use the two shafts to align and attach the mounting bracket by drilling two holes the proper distance apart. Drilling holes is pretty easy compared to cutting straight lines and I think most people are more likely to have a drill. If you use a piece of wood, the additional thickness can help the shafts to keep the wood perpendicular. You might not need any additional fastener, and the lack of fastener could help it return to a neutral position after operation rather than migrate. Also, slowing down the stepper motor can reduce unnecessary forces and the likelihood of malfunction.

I'd never trust that it will hold and detach without residue, but that is probably my ignorance talking...

I own a 3d printer which makes most of these projects look like the perfect fit for a 3d print (even when there are far simpler solutions). So that is what I'd do :)

I'd cut a block of wood to fit snuggly to the left of the knob, wedge it in place and screw the stepper in to that.

.....or just screw into the AC unit somewhere discrete and hope no one notices.

I discuss this quite early in the writeup. There is a whole section on why a smart plug will not work here.

This would be the route I took, but the op was scared of the plug. If their landlord does an inspection IDK that they'd love seeing a hacked power cable.

I'd basically get something like this [1] and then put it in the middle of a patch cable.

[1] https://www.amazon.com/Aeotec-Security-controller-electricit...

I had a chat with this with a friend the other day - I feel like I’m much happier to do this now I live in a dwelling on its own. I mess up, it’s my issue. You mess up in an apartment block, it’s a lot more people’s issue, who aren’t opting in to that risk.

The lack of feedback from the AC unit makes using a switched outlet potentially problematic. You really need to know the state of the compressor cycling before you go mucking with turning it on and off. (At least this was the case with the refrigeration compressors I am familiar with from my youth.) A current sensor could provide feedback but that goes beyond a regular smart switch.

30 years old PTAC has wired thermostat terminals. But I dolike OPs solution.

It's $7 part made of a tiny bit of metal.

If it was actually a $2 part, I'd agree with you. But it's enough that it's probably worth returning, especially since he had to try a few to get it right, and then he can return them all at once.

It's not his fault if it ends up in the landfill. That's on Amazon. Also, they have discount stores they ship returned stuff to before it hits the landfill.

Any reason why you didn't just use ESPHome for the firmware?

It even has a component specifically for the ULN2003 stepper motor driver you were using

https://esphome.io/components/stepper/#uln2003-component

There are no air ducts to move air between the units. They are old brick buildings and retrofitting central air you might as well tear down and rebuild a lot of the time.

I had the option to buy a “central” unit or several mini splits for my apartment. I chose several mini splits. The main reason is that they can fail independently, so I’m not stuck in an apartment that is hot everywhere.

But I think the main reason is that in places without central AC, people tend to want to incrementally upgrade. For example, you might get a mini split just for your bedroom, because that’s the room you require the most comfort during the hot days. Then when you start getting used to the comfort of the AC in the bedroom, you’ll want one in the living room. And so on.

I think what also plays a role is that this way each tenant gets charged for AC use through their own power bill. No difficult central accounting to do.

Still, split units are way easier and more efficient but I guess the landlords just go for the cheapest option.

Not in US, but on top of no room for air ducts, running long copper lines (for both mini split and multi-split units) tends to be expensive (price of copper). You also need to guide condensation out, so either downward piping or (expensive) water pumps everywhere. Installation ends up being more expensive than the AC system.

They are cheaper and easier to retrofit in existing buildings. The landlord pays for the installation of these units, but typically not the cost to operate them, so they are primarily concerned with optimizing install cost and have little to no concern for efficiency.

The Broadlink Rm4 Pro IR blaster puck includes an optional "Sensor Cable" which measures temperature and humidity directly. The initial setup via the app is terrible and requires location services for Wi-Fi pairing, but once that's done it has worked fairly well.

I had better luck for my use cases with the Aqara M2 Hub. I believe that device is discontinued, but they seem to have other very similar models. No built in climate sensors on that one, but the UX and IR signal response time have been much better overall.

I don't know if there is a pre-made solution but it's easily doable using something like an ESP32 or a Pico W and a little soldering. Maybe ESPHome has IR support but I used a micropython library and a spreadsheet to decipher a Mitsubishi Heavy IR remote. You can then use the same library to play a string of bits through an IR LED[1]. You can get IR receivers and transmitters for cheap on Amazon. You can pair that with any commonly used sensor (DHT22, HTU21, etc... I prefer the BME280), for all of which you can find libraries on GitHub and breakout boards cheaply online. Then you could either implement a small web server to control it standalone or an MQTT client to control it from i.e. Home Assistant. If you use an I2C sensor, and something like this[2] you don't even need to solder anything you can just connect it all using those DuPont cables and stuff it in a box.

[1] https://github.com/peterhinch/micropython_ir/issues/46 [2] https://www.tindie.com/products/maxmixproject/power-bus/

I tried that with one once back in the pre-bot days. While someone could certainly have made it work, I couldn't make sense of the IR commands with available tools and this model wasn't something that others had already figured out (I tried all that ESPHome included).

I thought about building my own controls for it: After all, it's just a compressor and a fan that are each controlled by relays -- how hard could it be to have them controlled by my relays? Or to have its relays controlled by my logic?

But then I discovered that this particular aircon would resume, with a delay[1], after a power outage.

So I turned it on and left it on, and put it on a smart plug. It turned out that this was Good Enough, and there was no drama. It just worked.

Plus, because Home Assistant: I was able to use a temperature sensor that I found available in the Alexa speaker that I already had on the night stand to prove that the overall concept worked. (I added a Zigbee temperature sensor later on.)

[1]: The compressor likes to stay switched off for awhile after it has been recently run. People sometimes like to make it sound complicated or mysterious, but: It's just to help prevent the compressor from trying to restart while from a resting position that is in the middle of a compression stroke. Doing that is harder on things than it could be in the best case, and it stalls the compressor in the worst case (which can then extend to exercising thermal and/or overcurrent protection).

But as long as there's a bit of a gap between runs, then that provides time for the high-pressure side to leak down so there's not so much to compress, and the compressor can restart without too much fuss. That's all; that's the whole merit. My aircon's irrevocable power-up delay handled that problem well-enough, but the logic could be scripted in HA's YAML with a helper if that were necessary.

Some ACs have UART interfaces inside that can be fairly easily hooked up to an esp32.

You could also buy an IR transmitter module from AliExpress and add a temperature/humidity sensor chip on I2C like an SHT41.

If you are not averse to an off-the-shelf solution, Broadlink RM4 PRO universal remote will do both IR and 433MHz wireless (records and replays codes). The temperature and humidity sensor which you can plug-in if you need it is sold separately though (Broadlink HTS2).

I use http://getmysa.com for this. they have their own app and scheduling, but i just automate mine via homeassistant

I've successfully emulated remotes with ESPHome + xiao seeed + basic IR diode. Dozen lines of YAML can turn it into a thermostat in Home Assistant.

Flipper Zero can record IR remotes.

I have been using Sensibo for years. Never had a problem.

Depends on the type of button, but conductive tape can work - https://alexmeub.com/automating-capacitive-buttons-with-swit...

> I'm pretty sure doing janky things to the AC you don't own is a lease violation.

Why? Not all "janky" things are the same:

* Sloppy changes to the internal 240V wiring: yeah probably a violation of the lease, and legitimately likely to burn the place down, with associated liability.

* Temporarily mounting to the exterior this mechanism that turns the knob shaft, with no changes to the wiring, no holes, no nothing. I can't think what grounds they'd have for considering this a lease violation or a reason to keep any of the security deposit, as long as you pop the original knob back on when you move out. And as inigyou pointed out, how would they even know?

You have to learn to ignore what the rules say and go after the practical reality. How will the landlord know you did this? They won't.

Why? A dual-hose portable is more efficient than a single-hose, but a PTAC should (in theory) be more efficient (and possibly quieter) on account of having the heat-emitting side of the cooling loop outside of the living space, which is closer to the ideal split system - though I suppose that advantage could be undermined by the unit's age and condition.

Portable ACs are generally less efficient than regular window ACs and PTAC units since the compressor is inside the room.

TFA mentions this.

You’ll need to unlock your iPhone for that.