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PWM Fan frequency and motor speed controllers

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read this https://aerocooler.com/delta-afc1212de-dell-p-n-y4574-120x38mm-extreme-hi-speed-fan-dell-5pin/

--- Quote ---It comes with 4 wire lead (white=TAC sensor, red=power, black=gnd, blue=PWM control) to 5 pin Dell connector
--- End quote ---
so blue is pwm control. here you apply the pwm. have you buyed yet something to drive the pwm, or do you already got some arduino/stm board?
if you do, get to work, write the controller, put the wires and it will do


--- Quote from: BinaryBits on October 20, 2021, 04:27:56 pm ---Thanks for the info, but the datasheet for the Delta AFC0912DE fan says "Caution: The lead wire of RD signal can not touch the lead wire of positive or negative"
After reading a bit of Delta documents it seems to mean "Rotational Detector, is that something different from the Tacho wire??

I checked the voltage on the two wires and the blue showed a steady 3.62V, and the yellow showed close to 0V, sometimes jumping around a bit? I suspect that the blue wire is PWM?

I tried the speed controller that I bought, with the black and red wire (DC control) at 25Khz, and it adjusts the speed of the fan, but not smoothly/linearly, firstly It can only go down to about 40% Duty cycle before the fan stalls/makes strange noises, and secondly after around 75% it feels as if the speed is not increasing anymore. So its not the ultimate way of controlling the fan.

That writeup I mentioned is also a dedicated PWM fan controller, the reason I liked that one was because it was very clear and helpful for a beginner like me, with a parts list and everything, and seemed extremely simple. I would gladly try to build the provided circuit by Ian.M, but unfortunately that circuit diagram alone is not enough for me to be able to build that particular PWM controller. Thats why I asked about the one I pointed too.

About the Arduino, I actually tried that earlier successfully with another PWM fan, which is only a 0.25A fan (but which draws only 0.09A at 12V), but I was afraid that the Arduino couldn't handle the 3A of the Delta fan, or maybe the Arduino part of the setup is not affected by the amp draw? Also I would need to be able to adjust the duty cycle externally through a potentiometer and not in software.

--- End quote ---
yellow is the output showing you some pulses mirroring motor rotation, if you put a pull-up resistor you'll see those pulses on scope (see page 7)

your speed controller adjust Vcc for your motor, it's not normal to control speed like this. NO NO NO. this motor is with FIXED voltage supply and his speed is imposed by driving PWM input (blue) like they say on page 8, not by changing Vcc on red pin.
leave the yellow alone for now (you won't monitor his speed, for now just set the speed you want with pwm control on blue wire), after succeding this control you can move to monitor if this speed is correctly done by the motor.

references are to the pdf to your actual motor, which are almost identical with the one i posted before.

maybe this will clear your ideas, exception is in your case your  yellow is the white wire from my example https://www.cgdirector.com/pwm-dc-system-fans/ or really basic and clear  https://www.ekwb.com/blog/what-is-pwm-and-how-does-it-work/

Yeah, the speed controller that I have now uses the fan in DC mode, i.e, only using the Red and Black wires of the fan, but it still has a variable frequency setting, and adjustable duty cycle, so if the speed controller only changes the voltage then what is the variable frequency and Duty cycle good for? Then it would be more like just a simple adjustable buck converter?
I understand its not a real PWM fan controller, this one I have now is mainly for control of motors.

I have not a real PWM fan controller yet, I want to try and build one with a 555/556 timer, I just must order the parts first. I already have an Arduino and have successfully driven another lower Amp PWM fan through the Arduino. But I would rather build a dedicated PWM controller, it feels cleaner and smaller footprint than an Arduino?

Okay so I need to have a resistor with the Tacho wire to get a "normal" output? I tried probing the Tacho wire with my cheap oscilloscope without an resistor and the trace didn't make much sense to me.
What value resistor would I need, or how should that be calculated?

sorry, but you don't get the idea. your fan is designed to operate not from 0 to 12Vdc, but from 8.0 to 13.2 Vdc, and to be controlled in speed by pwm pin.
i can't validate something that is bad engineering just because you insist.
finally, choose to regulate him as you please, i'll stop here, you already have all the info on the table.
from my part, you can regulate him with energy from santa-klaus, i explained how it's done correctly and how everyone else does it.

Maybe you didn't understood what I was writing, but nowhere have I insisted on running it in DC mode, thats just what I do right now because I don't have a real PWM fan controller, I have mentioned that I intend to build one though.

What I did though was questioning what the difference is between a motor speed controller and a buck converter?

And just like I have written in my previous comment I understand fully that a PWM fan is supposed to be run through the PWM control wire by adjusting the duty cycle, not by changing the voltage, but its hard to do that right now since I don't have the hardware to do that.

Thanks anyway.


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