Great! I can continue to avoid the Home Assistant time-sink…
Would this standalone mode support dynamic PWM fan speed curves according to temperature?
This is to be implemented but yes it would - I would have this feature running on the microcontroller instead of Home Assistant anyways.
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The prototypes are working nicely - total production & delivery very time was only 6 days from placing the order. I’m really impressed with the quality. I’ll do some full load tests and connect external temperature probes but it looks as if everything is working as expected.
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I’m new here and just wandered across this thread.
Great work!
I’ll sign up for a couple of the pcbs, once you’re happy with them.
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Even more interesting is the paper linked at the bottom of the article, which provides some basis for the greater perceived comfort of UFH vs radiators, as well as suggesting that fan-assisted rads offer significant benefits for low temperature heating systems.
I’ve already got some Noctua fans running, just need to make them more acceptably packaged!!
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I added a plinth heater in a room with two rads, and even though it has a similar maximum output to each of the two radiators, turning it on really does make a difference to how warm it feels, and quickly.
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I have incorporated a few changes. I got rid of the on-board temperature sensor; mainly because it prevented standalone operation with an additional external sensor on the radiator, the reason being that you have to enter each sensor’s unique ID in the ESPHome yaml if you have more than one sensor. Without the always-connected internal sensor, the first connected external sensor will be automatically picked up. As there is a second connector anyways (and you can put as many DS18B20 in parallel as you want), I think this sufficient.
I switched the screw terminals to direct plugin locking terminals because I found myself hunting for small screwdrivers in testing. This way there are no tools required.
Finally, as people might be using them with universal power supplies or old ones they have lying around, I decided to add in some reverse polarity protection.
I am placing an order of 20 today at JLCPCB and expect them to be delivered to by the end of next week. I already got some requests - anyone interested in getting one (or more) please DM me.
I have uploaded the KiCad design files on GitHub. ESPHome code will follow.
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I consider a great use of these would be letting a room be used as both bedroom and home office temperatures without TRV.
Yes, that works nicely. I have the fan of the bedroom on during the day to indirectly heat an adjacent room without radiator and turn it off before bedtime to have a better sleeping temperature.
A small update: The PCBs are in production, Lunar New Year delays it a little bit but the hardware should arrive next week. I actually included safety features that I wanted to do in a later revision (resettable fuse & transient voltage protection). While waiting I have implemented a full temperature curve control - you can define five temperatures & associated fan speeds and the fan speed is adjusted dynamically based on the current radiator temperature. I’m mostly envisioning this to decrease fan speed with increasing temperature in order to mitigate fluctuations due to cycling, but the behaviour is completely arbitrary and up to the user. This all works without Home Assistant or an internet connection. Stay tuned 
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Good news! Thank you!
Santa came today…either he’s real late or super early 
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I tested one of the 15 PCBs and it’s all looking good. Will test the others as well, flash the controllers and then I can ship them out next week.
Including customs fees + shipping to me, the price per controller including one temperature sensor came out to 35€/30£, a bit more than anticipated earlier. There’s definitely room for saving some money in the next version, but for now I’m quite happy. I’m not aiming to make any profit off these for now since this is just a hobby project, so I’m happy to send them out to anyone interested for the 35€ + shipping.
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Excellent! Can’t wait.
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Just ordered 2 of these smart little pcb’s and I’m looking forward to getting them going to see how they alter the heat distribution in our room.
Now I just have to spec some power supplies and try not to lose weeks to the fresh hell that is searching online for silent PC fans that don’t cost the earth.
Any wisdom that can shortcut that process gratetfully received.
B
The cheapest fans I am using are the Arctic P9/P12/P14 PWM fans. You can get a 5-pack for around 30€. Another nice feature they have is that you can cascade them, even though the controller has sufficient sockets, this allows you to just make a long line of fans that only occupy one socket. They are not the most silent ones but cost only half of others. Also they can run really fast (1800 rpm) and modulate down to 0 RPM. I’m using them in my living room running at 35% where they are inaudible, even without acoustic decoupling.
What size radiators do you have?
Regarding a power supply:
While some fans (e.g. be quiet Shadow Wings 140 mm) state a 0.3 A current rating, I have never observed that in practice. The integrated resettable fuse breaks the connection around 2.5A, which would in theory be 8 Fans @ 0.3A + the microcontroller. You’ll be fine with a 2A supply, though. You need a center positive plug (almost all are, so no worries). The wrong polarity won’t break controller or fans but it’s not gonna work. Also don’t use more than 12V.
Something like this will work Zolt 12V 3A Power Supply Universal AC DC Adapter Transformer with 9 DC Connectors for 12V 1A 2A 3A Household Electronics, 36W Max.: Amazon.co.uk: Electronics & Photo
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Noctua Redux PWM. 120mm for K2 rads, 140mm for K3.
I have added detailed setup instructions & a fan curve control tutorial to Github: GitHub - andrekuehne/openradfan: An ESPHome-driven controller for radiator fans to improve heat output. The KiCad design files were updated to the latest manufacturing run at JLCPCB. Also the full ESPHome yaml as well as factory & OTA images are available.
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This looks awesome!
Have you managed to ship any over to the UK yet? I’d love to give one a go. Currently have a speedcomfort running to test but I find the airflow quite poor. I’d like to try and replace it with one of these and a few decent fans
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Are most fans speed controllable with this, even if they maybe weren’t designed to be ?