I’ve been working on a similar setup using the M5Stack NanoC6 and AtomS3 Lite, and put together a parts list and wiring guide on my site: https://serin-labs.com/parts.html.
I also built a web flasher with firmware configured for those boards, so you can install directly from your browser without any fiddling or configuring. The ESPHome option uses the same echavet/MitsubishiCN105ESPHome project mentioned in the article. I also included a YAML generator for that project so you can more simply customize the config. There are also separate firmware options for HomeKit and Matter.
https://serin-labs.com/flash.htmlhttps://serin-labs.com/esphome/generate-yaml.html
I run Serin Labs and sell assembled kits and the cable separately.
For anyone with City Multi, P series, or M series systems with a branch box, you may also be interested in a multi zone controller I’m developing: https://serin-labs.com/multi-zone-controller.html. It connects to the system’s communication bus, allowing one device to control all zones without needing a CN105 adapter at each indoor unit. It also exposes operating data such as refrigerant pressures, temperatures, power, compressor frequency, and fault codes, with everything running locally. Software is still in development.
The Nano is fine to connect directly because it has diodes on the data pins but the S3 Lite needs a level shifter or it'll eventually stop communicating with the air handler.
yeah came here to say this, I have my mini splits set up on the S3 light with level shifters, not worth skipping because they'll end up failing on you - requires a little soldering but nothing complicated
HN is awesome sometimes, I actually just installed 3 of your devices in my ACs to get them all wifi enabled. Worked perfectly, thank you!
Is it possible to flash them from Google home firmware to esphome without USB? I might move away from Google home soon but I'd hate to have to reopen up my ACs again.
It's not possible to cross-flash a different firmware track over the air but since you're already using the Matter-compatible firmware, you can pair it directly with Home Assistant, fully local. It won't be as configurable as the ESPHome firmware, but it'll get you the controls you need.
I'm hoping to get a mini-split system installed soon and thought I might as well look for something with HA integration. It's not easy. Some manufacturers like Samsung actually want to charge you monthly for cloud integration! Completely out of the question obviously. I came across this, and Mitsubishi is supposed to be good anyway. I would prefer something that's actually supported but I can't seem to find any other options.
I could also very easily wire my units in so no need for WiFi. Maybe I can find a wired ethernet module.
My ideal system would be something that does matter over thread with zero external internet access. Matter over thread devices are all standardized so no proprietary app required, and the newer iphones have a thread radio built in so you can control them without even a hub.
I have my AC connected using Matter (over WiFi, not Thread) using esphome-matter, a relatively new extension to ESPHome + a small open PR [1]
Since it's running ESPHome you can easily verify everything it's doing.
Thread would be even better but this is good enough for me. 100x better than the original cloud app it came with. Still no proprietary app required, works on every platform.
I used this guys thing https://clima.protoart.net/ after someone mentioned it in an HN comment last summer, then used claude to extend it this summer. A year in, I’m very pleased. Matter or thread would be nice, but these are super straightforward out of the box and totally local.
The manufacturer documentation [0] for everything is great and it was perfect for my goal of getting them
to show up in Savant as native thermostats [1] (likely beyond typical scope for split units).
For anyone wondering why he would ever do this, it seems to be a type of hidden mini-split system used in euro-style shoebox flats, with a super-proprietary thermostat. Wi-Fi capability is an option at additional cost, but was not purchased.
In the USA, wired thermostats tend to use standardized 24V wiring schemes, or 208V/240V for mains voltage heaters (electric heat, common on the west coast, especially in shitty apartments, central hot water/steam heating is more common on the east coast).
I had this same control panel in Australia. The actual AC unit was part of the strata common property and I think somehow shared between multiple units on the floor.
FYI this kind of thermostat is actually better. American style thermostat put your HVAC system in either on or off state (basically PWM), whereas this kind of communicating thermostat can tell the system what the temperature is, so they adjust power accordingly. I do wish they have standardized protocol though.
Single stage hvac systems tend to have better performance in the max capacity cooling cases (Texas) and last significantly longer than units that rely on non-linear electronic devices.
The difference can be as extreme as 10+ years of service life. There are residential systems that were installed in the 80s and 90s that are still running fine today. The hermetically sealed scroll compressor is an engineering marvel. The electronics will generally fail before any meaningful mechanical wear is incurred.
>Single stage hvac systems tend to have better performance in the max capacity cooling cases (Texas) and last significantly longer than units that rely on non-linear electronic devices.
Because all too often the electronics are what fail and replacement parts are not available so the whole thing is scrap even though the compressor is still good.
Inverter systems have more conversion losses than single stage. Most of the time, I definitely intend to run my system as hard as it can. There are only 4-5 weeks out of the year where variable speed would make a meaningful difference.
Semiconductors wear faster than copper wires and contactors and are much harder to replace. I can take a part from my neighbor's condensing unit and it would almost certainly work in mine. The make/model is largely irrelevant. I can go on Amazon, search "Start+Run Capacitor" and buy the first thing I find.
Single stage forced air / air handlers AC systems are basically only found in North America because they are so grossly inefficient and because most people in the rest of the world realize they can save money by not having all of their rooms ran off the same system. The rest of the world runs on mini splits for that reason.
The thermostat is better only because it takes advantage of the inverter modulation capabilities in the heat pump. I don't have the sense that inverter modulation is the norm for most home ducted systems, even new builds in North America.
I've only observed ductless systems like this in retrofitted, older homes in Canada. And at that point they're usually not integrated with the home's existing heating system / thermostat.
Most new construction with heat pumps are going to have use similar thermostats, both because of improved efficiency since the outside unit wants to know how much heating/cooling load is being requested, and more importantly, because builders are lazy and would rather use a battery-powered wireless option instead of running thermostat wires.
Off the top of my head, Mitsubishi, Rheem, Lennox, and Carrier all have similar default options, with converter boxes for retrofits to 24V controls.
Is this "mini" split? This type of panels are pretty standard for office buildings in Japan. Usually networked into building management system somewhere. Most household mini splits come with an IR remote, and don't support these panels. Standalone third-party thermostats are rare.
People tend to mix the terms around a lot, but generally you'll see the manufacturers use "ducted split system" or "mini split", where mini splits are the self-contained wall or ceiling mounted units.
I live in an NYC apartment with a similar Mitsubishi ducted split system - very short run ductwork just because the apartment itself is small, but takes up way less space than traditional American-style air handlers, even the apartment sized ones. The entire air handler is suspended above my bathroom ceiling, in between the drywall and the slab above.
My system was originally installed with the 2-wire serial wall thermostat but I converted it to one of Mitsubishi's Redlink wireless units because I needed to relocate the thermostat. But since Redlink isn't wifi, and the Mitsubishi networked thermostats and cloud platform get pretty poor reviews... this project is super interesting to me.
Does anyone know if this could be used to "cap" the AC settings ? It could be useful in an airbnb place, where I want to limit the lowest (e.g. 18 degres Celsius) or hottest (e.g. 22 degres Celsius) the guest can set the AC.
To answer your question, yes you could certainly do that and override what ever the physical thermostat was set to. You could also set max hours per day (kWh)for usage or adjust for variable rate plans.
As with anything you'd need to test.
Edit:
Looking through the repo and the article I see nothing blocking you. You certainly won't break anything!
Apologies for the Claudish, especially if anyone wades through the blog posts. I cringe when I reread them, but having some documentation on a working system is better than the ~none I was publishing before.
My idea of HVAC is that it should be "set and forget", so "smart" is the polar opposite of what I want. The round Honeywell on the wall has been doing its job for the past few decades, and will likely last many more with only an occasional cleaning.
Isn’t this is only true with central air though? Most other types of ac are not full climate solutions to leave running all the time and need some manual control.
At least that’s how I use the mini split in my garage. I have to remember to give it 15-20 minutes headstart before I use the garage or will be really hot.
Check out Uncle Pennybags over here with AC in his garage...
All "smart" t-stats can be used in "dumb" mode but the remote control and monitoring is really the killer feature. Scheduling and presence is meh, if you're obsessed with energy savings I guess.
If you have same schedule every week, don't go on vacation, your kids don't have breaks, don't have seasons, then 'set and forget' dumb thermostat will work for you without any problems. For the rest of us we need some 'smartness' in our thermostats.
You shouldn't need to change the temperature regardless of those things. My house remains at 68-72F basically all the time. Thermal cycling accelerates aging of materials.
Do you have any citation for thermal cycling through the range of an AC inside a house affecting the failure rate of any household goods? Based on my experience this does not seem likely to be the case: thermal effects tend to be exponential or high powers of temperature, and most thermal cycling that people worry about is on the order of 100C or more. 10/20C of variation seems unlikely to be relevant.
But with most houses, the AC will cycle on and off throughout the day anyway - raising the temp while you're gone will often result in less cycling. Especially if you also increase the hysteresis range while out. So you get a triple efficiency win, from better AC efficiency, less AC motor wear, and less heat loss to the outside.
Isn't the thermal cycling greater outdoor than indoor because of the differences in the outdoor temperature between day and night? So most ordinary materials indoors should be fine with a delta of even 10 Kelvins/10 Celsius/18 F.
All of the material thermal failures I can think of come from localized and more extreme sources: electronics, lightbulbs, washing/drying clothes, washing dishes in a dishwasher. Water below freezing point too, but that's because the temperature fell below a threshold. None of these are from heating or cooling rooms directly with HVAC.
For some people they may only opportunistically (perhaps they have excess PV production at that moment) run their AC or temporarily turn it off when they temporarily have other power demands at that moment (eg running dishwasher, washing machine, microwave, kettle, etc) and don’t want to pay for grid energy while doing so.
“HVAC” is essentially not a thing in houses in South Africa likely due to having a mild climate, this also makes insulation in houses optional and mostly not done.
So most people with AC here are probably using it as a luxury and will happily have it be off a little if it meaningfully reduces energy usage while still making their house noticeably more comfortable.
This is exactly the case in my household. Excess solar is pretty much worthless here, so with a smart AC you can dump the excess solar into your house as either heat or cold. This (currently) has a lot better ROI than installing a household battery. (Battery tech and availability might change this.)
I am enamoured by making dumb AC's smart by this method, since you probably have a lot less IT risks than by using the suppliers app. I think the trade off is between IT risk and mechanical / technical risk, since adding your own parts have an effect on warranty (or at least: willingness to repair by the supplier).
Research it with an LLM. I've ordered all the stuff for Panasonic and Daikin after a deep planning session. It told me what connectors I need that Panasonic needs a level shifter. Both brands have open source libraries for the internal protocols and wiring. I wanted Zigbee so the ESP32 C6 was the way to go. The Panasonic units I have already have Wifi but most companies suck at this kind of thing. I couldn't get the Panasonic Wifi to pair with my router. Daikin also sell Wifi modules and people don't to like them.
I did similar with our coffee machine a year ago - I was bored of getting home from the school run to a cold pot of coffee because the machine automatically turns off the hot plate after 30 minutes, and it seems there is no such thing as a WiFi connected drip coffee machine. Kettles, yes, coffee machines, no.
Dead simple. Cracked it open, chucked an ESP32 in there connected to the soft power button, and to the “machine is on” indicator on the display, which was conveniently on its own pin. No need for any thermal protection cleverness as the machine does that itself.
Now I just turn it back on when I’m heading home, and no longer have to wait for the pot to warm up again.
I then decided to stop using the “make coffee at time” functionality baked into the machine, as the kid gets up when the kid gets up, and the machine would either start early and wake her, or she’d get up before it and I’d have to go start it. Now, she opens her bedroom door, I get “kid is awake” alert on my phone, and the machine brews the coffee.
Until the kid uses the bathroom in the middle of the night and goes back to bed. Though the GP seems to not mind stale coffee so perhaps he won't care.
Sure, but in home automation there was a whole lot of those didn't realize situations that you won't get right. In the one end I often go for the question, 'is it really worth the bother of trying to set this all up'?
In most cases, there's nothing wrong with the switch on the wall. I don't need a complex home automation. I do have Home Assistant. It isn't very useful. It's kind of nice to have a couple of lights on from dark until 9 p.m. but with the efficiency of modern LEDs, it's probably cheaper to just leave those lights on 24-7 than to leave my home assistant machine on 24-7.
I gate it exactly as the parent says - automation only runs between 0530 and 0800, and when we’re home.
I literally couldn’t do without HA - I live off-grid, and it manages everything from monitoring water tank levels & running pumps to a power grid distributed over three independent and geographically distributed battery banks. Monitors for anomalies and tells me what is acting up - for instance today I got sent on a mission to find out why an array of PV was underproducing by 33%. Wouldn’t have noticed until it started having energy budget impacts otherwise. Makes decisions on whether today is a passive cooling/heating day or whether we have the energy budget to run climate control, when windows should be opened/closed to maximise efficiency, which blinds to close when depending on where the sun is to prevent or encourage passive solar gain, when to run the partially pumped storage hydro and in which direction, when to pull the pin on the deluge system and where if it’s set to wildfire mode. It has literally saved the house - not our lives, as we’d already evac’d and left it in charge of firefighting.
Stuff like the coffee machine and opening the blinds in the morning are just easy quality of life improvements, something less to have to manage manually, as my days are full enough that removing any point of friction is useful.
And yeah, I’ll take slightly stale coffee now over fresh coffee in ten minutes.
Mitsubishi AC units that support M-NET have a CN105 port. IIRC, my specific model uses a JST PA 5-pin connector rather than a JST PH 5-pin.
As a small hack, I used the Python scripting interface in Home Assistant to replicate this [1] feature from Panasonic HVAC that gradually raises the cooling set point towards the morning. It is quite comfortable during the summer.
This is kinda unrelated but I learned while researching for my new AC that there are two Mitsubishi brands/companies, one is Mitsubishi Electric and the other is Mitsubishi Heavy Industrial. And their ACs are not the same, so just saying Mitsubishi AC probably could lead to problem. The one OP has is Mitsubishi Electric by the first photo.
Technically, they’re both part of the Mitsubishi Group, the former zaibatsu; there are number of other Mitsubishi companies in this conglomerate as well.
However, the Mitsubishi Pencil company is entirely unrelated to the Mitsubishi Group. Ironically, they share a very similar three diamond logo, which they registered and used years before Mitsubishi Group.
These mini split inverter units seem to be good for +/- 1 C, but the 2 C swing can feel quite substantial.
PID control seems to be lacking overall, the control laws seem to be more basic. In particular, my unit waits until temperature deviation from setpoint exceeds 1C before cycling on. If I want finer control, there are a few options I can think of:
1. Spoof the temperature, add a TEC , heater, cooler or something to the sensor on the remote
2. Manipulate the controller buttons, change the setpoint down or up by 0.5 degrees so the unit kicks on after a 0.5 degree change instead of a 1 degree change
3. Spoof the temperature sensor itself, hack into the wiring with some transistor based circuit
4. Hack into the actual unit, fully take over the compressor and fan control
5. Buy a better unit or off the shelf controller
6. Spoof the remote control, reverse engineer the IR communication temperature signal
This last option seems the least intrusive and cleanest, I see other people have done it, it's definitely a lot of work even with AI.
If anyone is looking for something similar it's worth looking into A somewhat less complex solution that preserves all functionality. Use the IR receiver plus a broadlink IR Hub. You can meet all the goals here, run it all locally the only downside is no 2 way communication. So if you do change the thermostat via the wall it won't be reflected in your app.
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[ 0.25 ms ] story [ 41.2 ms ] threadI also built a web flasher with firmware configured for those boards, so you can install directly from your browser without any fiddling or configuring. The ESPHome option uses the same echavet/MitsubishiCN105ESPHome project mentioned in the article. I also included a YAML generator for that project so you can more simply customize the config. There are also separate firmware options for HomeKit and Matter. https://serin-labs.com/flash.html https://serin-labs.com/esphome/generate-yaml.html
I run Serin Labs and sell assembled kits and the cable separately.
For anyone with City Multi, P series, or M series systems with a branch box, you may also be interested in a multi zone controller I’m developing: https://serin-labs.com/multi-zone-controller.html. It connects to the system’s communication bus, allowing one device to control all zones without needing a CN105 adapter at each indoor unit. It also exposes operating data such as refrigerant pressures, temperatures, power, compressor frequency, and fault codes, with everything running locally. Software is still in development.
Is it possible to flash them from Google home firmware to esphome without USB? I might move away from Google home soon but I'd hate to have to reopen up my ACs again.
It's not possible to cross-flash a different firmware track over the air but since you're already using the Matter-compatible firmware, you can pair it directly with Home Assistant, fully local. It won't be as configurable as the ESPHome firmware, but it'll get you the controls you need.
I could also very easily wire my units in so no need for WiFi. Maybe I can find a wired ethernet module.
There's no Internet from the IoT SSID.
Since it's running ESPHome you can easily verify everything it's doing.
Thread would be even better but this is good enough for me. 100x better than the original cloud app it came with. Still no proprietary app required, works on every platform.
[1] https://github.com/DavidvtWout/esphome-matter/pull/53
The manufacturer documentation [0] for everything is great and it was perfect for my goal of getting them to show up in Savant as native thermostats [1] (likely beyond typical scope for split units).
[0] https://protoart.net/knowledgebase/me_cn105_ata_wifi_http_ap... [1] https://github.com/samstevenm/minisplit-local-public
Their official service needs an app and cloud access to control it. And I absolutely refuse to do that.
https://codeberg.org/RevK/ESP32-Faikout
In the USA, wired thermostats tend to use standardized 24V wiring schemes, or 208V/240V for mains voltage heaters (electric heat, common on the west coast, especially in shitty apartments, central hot water/steam heating is more common on the east coast).
The difference can be as extreme as 10+ years of service life. There are residential systems that were installed in the 80s and 90s that are still running fine today. The hermetically sealed scroll compressor is an engineering marvel. The electronics will generally fail before any meaningful mechanical wear is incurred.
Why?
Semiconductors wear faster than copper wires and contactors and are much harder to replace. I can take a part from my neighbor's condensing unit and it would almost certainly work in mine. The make/model is largely irrelevant. I can go on Amazon, search "Start+Run Capacitor" and buy the first thing I find.
I've only observed ductless systems like this in retrofitted, older homes in Canada. And at that point they're usually not integrated with the home's existing heating system / thermostat.
Off the top of my head, Mitsubishi, Rheem, Lennox, and Carrier all have similar default options, with converter boxes for retrofits to 24V controls.
I live in an NYC apartment with a similar Mitsubishi ducted split system - very short run ductwork just because the apartment itself is small, but takes up way less space than traditional American-style air handlers, even the apartment sized ones. The entire air handler is suspended above my bathroom ceiling, in between the drywall and the slab above.
My system was originally installed with the 2-wire serial wall thermostat but I converted it to one of Mitsubishi's Redlink wireless units because I needed to relocate the thermostat. But since Redlink isn't wifi, and the Mitsubishi networked thermostats and cloud platform get pretty poor reviews... this project is super interesting to me.
Edit: Looking through the repo and the article I see nothing blocking you. You certainly won't break anything!
Apologies for the Claudish, especially if anyone wades through the blog posts. I cringe when I reread them, but having some documentation on a working system is better than the ~none I was publishing before.
At least that’s how I use the mini split in my garage. I have to remember to give it 15-20 minutes headstart before I use the garage or will be really hot.
All "smart" t-stats can be used in "dumb" mode but the remote control and monitoring is really the killer feature. Scheduling and presence is meh, if you're obsessed with energy savings I guess.
All of the material thermal failures I can think of come from localized and more extreme sources: electronics, lightbulbs, washing/drying clothes, washing dishes in a dishwasher. Water below freezing point too, but that's because the temperature fell below a threshold. None of these are from heating or cooling rooms directly with HVAC.
“HVAC” is essentially not a thing in houses in South Africa likely due to having a mild climate, this also makes insulation in houses optional and mostly not done.
So most people with AC here are probably using it as a luxury and will happily have it be off a little if it meaningfully reduces energy usage while still making their house noticeably more comfortable.
I am enamoured by making dumb AC's smart by this method, since you probably have a lot less IT risks than by using the suppliers app. I think the trade off is between IT risk and mechanical / technical risk, since adding your own parts have an effect on warranty (or at least: willingness to repair by the supplier).
Dead simple. Cracked it open, chucked an ESP32 in there connected to the soft power button, and to the “machine is on” indicator on the display, which was conveniently on its own pin. No need for any thermal protection cleverness as the machine does that itself.
Now I just turn it back on when I’m heading home, and no longer have to wait for the pot to warm up again.
I then decided to stop using the “make coffee at time” functionality baked into the machine, as the kid gets up when the kid gets up, and the machine would either start early and wake her, or she’d get up before it and I’d have to go start it. Now, she opens her bedroom door, I get “kid is awake” alert on my phone, and the machine brews the coffee.
Out of all of the smart home threads and articles I've read over the years this is the only sentence that made me wish I had it. It's genius
Exceptions like the above make automations hard.
So... just make sure the automation only becomes available from ~6 AM to 8 AM. ;)
In most cases, there's nothing wrong with the switch on the wall. I don't need a complex home automation. I do have Home Assistant. It isn't very useful. It's kind of nice to have a couple of lights on from dark until 9 p.m. but with the efficiency of modern LEDs, it's probably cheaper to just leave those lights on 24-7 than to leave my home assistant machine on 24-7.
I literally couldn’t do without HA - I live off-grid, and it manages everything from monitoring water tank levels & running pumps to a power grid distributed over three independent and geographically distributed battery banks. Monitors for anomalies and tells me what is acting up - for instance today I got sent on a mission to find out why an array of PV was underproducing by 33%. Wouldn’t have noticed until it started having energy budget impacts otherwise. Makes decisions on whether today is a passive cooling/heating day or whether we have the energy budget to run climate control, when windows should be opened/closed to maximise efficiency, which blinds to close when depending on where the sun is to prevent or encourage passive solar gain, when to run the partially pumped storage hydro and in which direction, when to pull the pin on the deluge system and where if it’s set to wildfire mode. It has literally saved the house - not our lives, as we’d already evac’d and left it in charge of firefighting.
Stuff like the coffee machine and opening the blinds in the morning are just easy quality of life improvements, something less to have to manage manually, as my days are full enough that removing any point of friction is useful.
And yeah, I’ll take slightly stale coffee now over fresh coffee in ten minutes.
As a small hack, I used the Python scripting interface in Home Assistant to replicate this [1] feature from Panasonic HVAC that gradually raises the cooling set point towards the morning. It is quite comfortable during the summer.
[1]: http://getnavi.jp/appliances/681340/ (ja)
However, the Mitsubishi Pencil company is entirely unrelated to the Mitsubishi Group. Ironically, they share a very similar three diamond logo, which they registered and used years before Mitsubishi Group.
PID control seems to be lacking overall, the control laws seem to be more basic. In particular, my unit waits until temperature deviation from setpoint exceeds 1C before cycling on. If I want finer control, there are a few options I can think of: 1. Spoof the temperature, add a TEC , heater, cooler or something to the sensor on the remote 2. Manipulate the controller buttons, change the setpoint down or up by 0.5 degrees so the unit kicks on after a 0.5 degree change instead of a 1 degree change 3. Spoof the temperature sensor itself, hack into the wiring with some transistor based circuit 4. Hack into the actual unit, fully take over the compressor and fan control 5. Buy a better unit or off the shelf controller 6. Spoof the remote control, reverse engineer the IR communication temperature signal
This last option seems the least intrusive and cleanest, I see other people have done it, it's definitely a lot of work even with AI.