Hello,
recently I gto 3 heater's blower motors from Volksvagen.
There are pictures and all in the second post.
I did some reverse engineering - these motors are really useful for projects that require a motor with a turbine for various ventilation (or other purposes).
And they are dead cheap, mechanically sound and ready to use after cleaning.
I got interested how the thing works, so I reverse engineered them - which was quite a feat as the PCB is tightly potted.
After I mostly destroyed the first one and stabbed myself in the finger with a scredriver,
I did the second one better after I discovered that the potting compound becomes very soft after hot air treatment.
Then I burned my finger
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
on my hot air station, which was about 400 C.
It felt more like electric shock rather then the usual burning sensation. And it sizzled...
With the price of the aforementioned personal injuries, I present to you the schematic of the thing,
which I believe is accurate. Checked it 10 times, found mistakes and corrected them.
But there might be some that slipped my attention.
I have some question though - I am not very good in analogue stuff and power supplies.
* why there are two MOSFETs in parallel?
* Why there are two op-amps? It seems like U1B is just for sinking current? Is it a protection from short circuit and over heating?
* in general how the whole thing works - it seems the op-amps are comparators, I does not seem that there is any feedback. Just capactitors - I guess for stability.
Some info from my tests:
-> At about 3.8V at the CTL pin the motor has sufficient current and starts to spin
-> At about 4.2V it is at max and consumes about 4 amps. (It actually triggers the over
current protection on my supply, so I can't say for sure if it is max and how much current it will take.)
-> The ramp up in speed from is pretty fast, though it feele linear.