What is "mains level" and "mains-capable"?Generally AC fans use a capacitor bank to alter the fan's speed. The switch connects the capacitors in various combinations to achieve the desired output.
Since the switching is done at mains level you need mains-capable relays, and a safe enclosure. You can replicate the rotary switch contact configuration with several relays and use them in place of the switch. Don't forget, when you start the fan you must select the fastest speed first, then turn down to lower speeds if desired. The high speed setting gives enough power to the motor to get the fan moving.
Probably you should get a new fan with infrared, Bluetooth, or WiFi control. Then you won't risk killing or injuring yourself.
Would the rotary switch be a simple switch or is there something else in the switch portion of the circuit. Where is the "capacitor bank" located, in the switch box or the fan motor housing?
Like I said before, there is the AC coming from the wall outlet and into the little switch box. From the switch box one wire goes out, but I have to assume it's a multiple wire cable. This multiple wire cable goes into the fan motor housing in the center of the box fan.
Is it safe to assume that the switch box is just a simple switch? Because then, I could really go for the relay solution.
So, I'm assuming that in the situation you mention, the "different windings on the motor" would usually be in the center fan motor housing, right?Most of the cheap ones I've seen switch between different windings on the motors. No capacitors involved.Generally AC fans use a capacitor bank to alter the fan's speed. The switch connects the capacitors in various combinations to achieve the desired output.
The relay advice given is still applicable in this case.
I actually did this for my deadbolt. I got the 35 lb. servo and screwed it into a kind of "U" shaped square bracket. So the servo fits "center-to-center" in front of the deadbolt handle. I really just zip tied and super-glued the two "arms" of the servo to the two arms of the deadbolt handle. I grinded an exaggerated bevel in the bolt and really hit the keyhole with the graphite just so it doesn't get jammed. I even have a sensor for the door to ensure it's closed completely before the deadbolt handle gets turned.Or go the simple way: use a Servo Motor and mechanically connect this to your existing switch. Either look for cheap SG90 or more powerful MG995. Or others. The mechanical parts could be produced with a 3D-printer...
But, I only did this because the deadbolt is completely mechanical. Since the fan is controlled electrically, I'm going with the relays.
Statistics: Posted by OCDelGuy — Sat May 24, 2025 6:56 am