I just bought a reversible flow dc fan (Sanyo Denki 9RFA1312P3G001) and I’m looking for a way to wire it.
It has 4 wires (PWM) and according to explanations from SD website for PWM “regular” fans is clear which wire is what. But, for reversible fan wires??? Nothing. Should I switch polarity to reverse the flow?
The answer to your question is found in the below excerpt from p1 of the datasheet. Both fan speed and direction are controlled via the PWM input, with zero-speed correlating to a near-50% duty cycle, 0% and 100% duty cycle to full speed in their respective directions.
No, that will not work. That will just short the Red + and Black - leads together. You can not use a ON-OFF-ON switch to change the direction of this fan.
You have to have an actual PWM signal going into the brown lead, so the fan knows what direction and speed you want. Looks like it needs to be a 25KHz PWM frequency, and it is usually a square wave signal.
“Correctly wired” can mean different things depending on your objective, but the description isn’t likely to be part of that category, since one of the switch positions would short-circuit the power supply.
A DPDT switch with center-off position could be used to provide FWD-OFF-REV operation, if wired as shown below. Variable speed operation would call for generation of a PWM signal.
Thanks for the information!
You’re right, what was I thinking… Anyway, I have some PWM controllers (alibaba provenance).
The all have DC IN (+ & -) and Motor OUT (+ & -), … I guess that of PWM controller woudn’t work with my fan?
Those would operate on the principle of directly manipulating the power supply to the device, and would not work with this fan. May cause damage actually, since fans of this type are not designed to have the power supply leads reversed.
A suitable PWM controller could be built however, using a 555 timer and a handful of external parts.
… but connected this way, I only get rotation on the reverse sense (brown wire). When I flip the switch on the other position no rotation whatsoever. I think I’m missing something, but I don’t know what exactly. Any instruction will be appreciated. Thank you!