AC Fan motor speed control ideas

[redwire]

Re: AC Fan motor speed control ideas

A phase-controller (dimmer) will always be noisy due to the sharp pulse, which makes the motor buzz. I use one in summer on my window fan.

You could use a variac, or transformer to cut back to say 160VAC, or put a series capacitor to the motor to slow it down. If you have any motor caps, try a 5uF or something.

[Dannyx]

Re: AC Fan motor speed control ideas

I guess I could also try a regular transformer ? Not as cheap as the dimmers, but not as expensive and overkill as a full-sized variac either. Of course, I'd be stuck with the single fixed output voltage, so I'd have to find the sweet spot where the noise/speed are both acceptable. I think this was around 70v in my case.

I also found these things but I have no idea what they are and how it would be possible to hook one up with all those wires. I guess they're for a specific type of motor, since they mention a capacitor....

[eccerr0r]

Re: AC Fan motor speed control ideas

Yes these tiny boards all tend to be TRIAC phase control lamp dimmer circuits just like the wall mount.

If cheap is the only way to go, that's what you get with phase control. The buzzing is expected, you can stick a inductor in series to dampen out some of the buzzing. Probably have to hack the pot/series resistor for more reasonable values for your motor - system behavior depends on the motor, control device, and also the load... together...

There are specially made "motor" "dimmers" that you can get too... usually they're like "high" "medium" "low" "off" and not a continuous function in between.

[Dannyx]

Re: AC Fan motor speed control ideas

But it could also be a lamp in the case of the dimmer

Here: I drew the schematic for the ones I got off Aliexpress. They look about the same, save for the snubber (?) network on the left and the dual pot setup on the right (RV1 is a trimmer). I didn't bother to add values for the components too, so they're just as kicad spat them out....

[petehall347]

Re: AC Fan motor speed control ideas

M1 appears to be a motor

[Dannyx]

Re: AC Fan motor speed control ideas

I belive that is a "dimmer", is it not ?

[petehall347]

Re: AC Fan motor speed control ideas



http://electronics-diy.com/schematic...controller.png

[Dannyx]

Good day folks. What I'm trying to achieve may seem pretty simple and although I found lots of discussions on the topic, it's hard for me to settle on a definitive answer, so I thought I'd ask for more opinions.

I have a small inline duct fan which looks like this, which I want to slow down, the reason being overall noise. I have no idea what type of motor this is, because I can't exactly take it apart to inspect it without ruining it, but perhaps we can work it out by examining its behavior.

Two things I've tried: a variac and a cheap light dimmer (triac+diac inside of it). The variac worked great: as I lowered the voltage, the fan slowed down and didn't give off any immediate signs that I shouldn't be doing what I was doing.

The dimmer was less than ideal: other than the fact that the motor slowed down considerably as soon as I moved the slider a small fraction, which made the slider virtually useless, the motor buzzed quite noticeably and I was afraid to let it run like this for too long, fearing the triac might pop.

I also have one of these that I could try, but I reckon it's the same exact thing as the dimmer I just tried, since I see the same exact components, with the exception of the inductor. The light dimmer also has a large inductor, but other than that, they seem virtually identical: diac, triac, potentiometer, capacitor. I heard about different kinds of dimmers and stuff like "phase angle control", but wouldn't know how to measure and analyze any of this stuff without a scope, which I don't have. I think all garden-variety hardware store dimmers will be like this and wouldn't be much better...

Based on these observations, I believe we're dealing with a shaded pole motor ? The variac (transformer) solution seemed to work the best, but I'm definitely not going to dedicate a big variac to this one sole use, neither am I willing to invest in VFDs to drive a small motor, so I think I'll have to compromise.....