DC fan controller - how to start figuring out what to do | Home Assistant | Page 1

formal mesa Oct 29, 2025, 5:28 PM

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OK, So I've bought two DC ceiling fans - they're basically the only game left in town for decent quality ceiling fans now. I have one here - and the controller partially disassembled (it's going to be a couple of weeks before they go into the ceiling). How do I start figuring out how I might control it in home assistant.
The fan controller is a "Carewell technology DC8-116MR-60TN29-L-D". I haven't checked the second fan, but I suspect a very similar controller. It has 3 wires going to a BLDC motor (they're labelled as such anyway) as well as control for the light. The wires look to be soldered to the "high voltage" side of the board, I can see the cut before it disappears behind a shield I'd rather NOT remove unless it's the only way. I've attached a couple of pictures that might help. I suspect this is a PWM driven BLDC, just based on my crude knowledge of circuit boards from watching too much big clive. Is there any hope that this can be controlled by home assistant without a janky RF based solution where I emulate the remote?

lilac fjord Oct 29, 2025, 5:45 PM

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formal mesa OK, So I've bought two DC ceiling fans - they're basically the only game left in...

are you looking to control the existing controller?
or replace theccontroller with a custom setup to drive the fan/light?

formal mesa Oct 29, 2025, 5:49 PM

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OK. I'm attaching a couple more pictures, my curiosity got the better of me and that shield was very easy to extract without damaging the sticker holding it on.. It claims to have wifi?!

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hang on, getting the pictures to discord.

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this is the controller side, under the rf shield. as you can see, there's some wifi stuff here? pretty sure a 27.1412G crystal is a sure sign of wifi?

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as for what to do - i don't know? Is there a replacement controller? I haven't found anything much. Is this a possible candidate for firmware hacking that holtek arm chip?

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i would like to see the fan as a fan in HA, as well as the light, and be able to control it. preferably without nuking the existing control scheme (a stupid little rf remote).

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interestingly, there's nothing on the back, except these big pads that are exposed through the case - perhaps a JTAG header or something?

lilac fjord Oct 29, 2025, 5:56 PM

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realistically I think hacking the onboard chip is not the approach to take

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making a custom controller is likely easier

formal mesa Oct 29, 2025, 5:57 PM

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this is the back. the cluster of rounded pads are exposed to the exterior of the case. that unpopulated chip seems to be connected to the holtek. perhaps the wifi module would be there?

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very possibly a custom controller would maybe work - i do have a simple oscilloscope so i could see what the motor and light signals are doing...

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it's disappointing no one seems to have moved into this market. dc fans seem to very much be the future of ceiling fans, but no one sells controllers for them.

lilac fjord Oct 29, 2025, 5:59 PM

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the board is used for multiple things most likely so has some unpopulated stuff

formal mesa Oct 29, 2025, 5:59 PM

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i'm sure it is

lilac fjord Oct 29, 2025, 6:00 PM

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so the device is 2 devices really
the light and the fan

formal mesa Oct 29, 2025, 6:00 PM

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yup.

lilac fjord Oct 29, 2025, 6:00 PM

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lets start with light

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white/blue go to light.
is the LED driver on that board or is it in the fan/light (which means the cables are just dc power)

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or even AC i guess

formal mesa Oct 29, 2025, 6:02 PM

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there seems to be a blank chip that is driving the LED wires - my guess is that's an LED driver, and it's being controlled pretty directly from the holtek

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it's all on this board. the input is Live Neutral Earth 110VAC

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(i'm just crudely tracing where the pcb traces go)

lilac fjord Oct 29, 2025, 6:03 PM

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then for the fan. you have 3 wires
the "mv" red wire is likely voltage but the other 2 we cant be sure of as theres aa few different setups for 3 wire dc motors

formal mesa Oct 29, 2025, 6:04 PM

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the other two are MU and MW

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they're being controlled by the six mosfets

lilac fjord Oct 29, 2025, 6:04 PM

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yeah but that might as well be dog and cat

formal mesa Oct 29, 2025, 6:04 PM

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which in turn are being driven by some sort of chip in pairs.

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i think they're being driven as a three way PWM - i don't think there is any independent voltage here.

lilac fjord Oct 29, 2025, 6:05 PM

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it could be ground and feedback
or
it could be forward and reverse
or
something else entirily

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if they are both going through mosfets then more likely forward/reverse

formal mesa Oct 29, 2025, 6:05 PM

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i'm pretty sure you can drive a three pole BLDC with 3 phases can't you?

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if you look on the second last picture - there's six mosfets on the left side. they go to the three wires via the choke coil

lilac fjord Oct 29, 2025, 6:07 PM

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at this point i would open up the light/fan part and see how the 2 cables connect to the led array and see if theres anything going on there and also get the model of the motor and look up a data sheet for that

formal mesa Oct 29, 2025, 6:08 PM

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i'll see what i can do

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this is the line of six mosfets and three motor drivers?

lilac fjord Oct 29, 2025, 6:09 PM

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then just build a controller that drives the led/fan based on an esp32

formal mesa Oct 29, 2025, 6:09 PM

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yeah, maybe.

lilac fjord Oct 29, 2025, 6:10 PM

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if you can get a datasheet for the motor that will give you some idea of what your looking at

formal mesa Oct 29, 2025, 6:10 PM

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https://datasheet4u.com/datasheet-pdf/BPS/BP6911/pdf.php?id=1551573 this is those three BP6911 chips. half bridge motor drivers.

BP6911 - 600V Half-Bridge Pre-Driver | BPS Datasheet

Download BP6911 datasheet (PDF). 600V Half-Bridge Pre-Driver by BPS. Includes specifications, pinout, and typical applications.

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can't get to the motor - it's a fully sealed unit 🙁

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(i'm sorry, but i'm not taking a dremel to my new light and fan fixture)

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just looking at 3phase bldc motor controllers - we seem to be missing angular sensing?

lilac fjord Oct 29, 2025, 6:20 PM

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you could try scoping the signals to work out what they are doing. be careful though some stuff like this has the dc ground referenced to ac neutral which means stuff might be live at mains even if its dc

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i cant tell if there is full ac/dc seperation or not

formal mesa Oct 29, 2025, 6:21 PM

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there's almost definitely not full separation. the HVLV slot is halfassed at best.

lilac fjord Oct 29, 2025, 6:29 PM

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you could try piggybacking an esp32 on this circuit
breaking it down you need a way to detect state and a way to send commands
you can likely find ways to detect the state by monitoring voltages in various places.
for sending commands you could look into how the rf sends data to the microcontroller. is it just setting pins high/low or is it an actual data signal

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if its just setting pins high/low for a moment on button press then thats easy to intercept. if its data then is it maybe i2c?

formal mesa Oct 29, 2025, 6:30 PM

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OK. i've identified all the chips on this board. there's the six mosfets for driving the fan from some sort of high current or voltage source (hard to tell). there's the three bp6911 chips for driving the mosfets from a signal (PWM?). Those seem to be directly plumbed into the holtek chip. The RF is handled by the CMT2210 i think.

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the cmt2210 is also directly plugged into the holtek chip

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i think piggybacking the cmt2210 with an esp would possibly be the best way?

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http://www.cmostek.com/download/CMT2210LH.pdf

lilac fjord Oct 29, 2025, 6:32 PM

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formal mesa i think piggybacking the cmt2210 with an esp would possibly be the best way?

it would let you send commands. but you would still have to seperate read the state

formal mesa Oct 29, 2025, 6:32 PM

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yeah. i'd need to figure out how to get that from the holtek

lilac fjord Oct 29, 2025, 6:33 PM

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i would detect it independantly from the output cables

formal mesa Oct 29, 2025, 6:34 PM

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i suspect they've got high voltage on them. i would probably rather watch one of the phase controller bp6911 chips

lilac fjord Oct 29, 2025, 6:35 PM

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you will have to isolate connects to the board anyway cos got only knows what gnd is referenced to and you would have to probably add your own power supply for the esp

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which you could drive directly from the ac

formal mesa Oct 29, 2025, 6:35 PM

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there's a pretty solid 12v dc power chip on here. i think it's powering the low side circuitry

lilac fjord Oct 29, 2025, 6:36 PM

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there gotta be 5v generation somewhere for the CMT2210 too

formal mesa Oct 29, 2025, 6:37 PM

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this bp85256 may have both?

lilac fjord Oct 29, 2025, 6:38 PM

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looks like its just 12

formal mesa Oct 29, 2025, 6:42 PM

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yeah. i think there might be a small 12->5 voltage regulator on this board somewhere. sadly it's at least 4 layers, so it's difficult to tell what's getting power from where.

lilac fjord Oct 29, 2025, 6:43 PM

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you can try and read the data out pin of the CMT2210 then find a way to emulate that

formal mesa Oct 29, 2025, 6:43 PM

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that's what i'm thinking to do for the esp.

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gotta figure out the feasibility of piggy backing an esp into this enclosure.

lilac fjord Oct 29, 2025, 6:44 PM

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if it doesnt fit then could always put esp in its own box stuf on the side then drill a hole for cables

formal mesa Oct 29, 2025, 6:45 PM

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yeah. if i can figure out how to get the signals and power out, i think i have space in the overall enclosure. it's a LOT smaller than the old AC fans it's replacing 🙁

lilac fjord Oct 29, 2025, 6:46 PM

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for the light state you can probably use a transistor activated when its on

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fan speed is a bit more tricky

formal mesa Oct 29, 2025, 6:47 PM

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it's a dimmable light, but i think i can figure that out pretty easily. it looks like a pretty simple LED driver circuit.

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as you say, the problem is the fan speed. i'd likely need to tune the ADC that i add to the driver.

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hang on. thinking about it, i might need to do more on the LED light too. i think it might have selectable colour temp

lilac fjord Oct 29, 2025, 6:49 PM

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with only 2 wires to it? not likely unless thee fitting is doing something activly

formal mesa Oct 29, 2025, 6:49 PM

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yeah. i wonder

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there's chips on the light. hmmm

lilac fjord Oct 29, 2025, 6:52 PM

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was thinking you could split the led off to a seperate driver. so this board is only doing the fan
then you could measure the power consumption of the device which will be different depending on which setting the fan is on

formal mesa Oct 29, 2025, 6:52 PM

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light

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so i think it's just sending high voltage straight to the LED panel. interesting.

lilac fjord Oct 29, 2025, 6:57 PM

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yeah i think iits just a 2wiree panel being driven by the board

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which means you can probably split that out fairly easy with any led driver you like

formal mesa Oct 29, 2025, 6:57 PM

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i guess they have some signalling protocol it's using to send it dim and temp info

lilac fjord Oct 29, 2025, 6:59 PM

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perhaps. i imagine its 12v mind. and the 12v psu mentioned earlier drives it

formal mesa Oct 29, 2025, 6:59 PM

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quite possibly. though there's basically separate circuitry on the LED side - so maybe not the 12v

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and the mosfet on the LED board definitely can handle HV

lilac fjord Oct 29, 2025, 7:00 PM

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yeah the voltage is probably pumped so that the right voltage is across each led

formal mesa Oct 29, 2025, 7:01 PM

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i'm not hitting a lot of good info on these two ketnus chips :/

lilac fjord Oct 29, 2025, 7:03 PM

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to be fair, we are probably a bit beyond the HA scope at this point into full reverse enginnering of stuff. you could ask over on the ESPHome discord about engineering an esp into it

formal mesa Oct 29, 2025, 7:03 PM

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yeah, i think i probably will...

lilac fjord Oct 29, 2025, 7:04 PM

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some of the people over there will know this kind of hardware project better

formal mesa Oct 29, 2025, 7:04 PM

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it's an interesting problem tho, and one that's gonna bite more as dc fans take over the market.

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those AC fan controllers are great, but they're completely incompatible with this tech.

lilac fjord Oct 29, 2025, 7:05 PM

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if the fittings standardise a bit then someone may make a replacement controller for them that can be a drop in replacement

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but chances of that happening is well... unknown at best

formal mesa Oct 29, 2025, 7:06 PM

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yeah indeed. it seems pretty unlikely looking at this mess of stuff.. anyway, i'll see you on esphome later. i have tyres to go swap for winters RN.

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thanks for the chat. it's been enlightening... this project is definitely not over yet.

#DC fan controller - how to start figuring out what to do