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Topic: speed control of ceiling fan using digital Potentiometer  (Read 3482 times) previous topic - next topic


I'm sorry, I'm not sure what you are trying to say.
I thought it was pretty clear. Maybe you only speak PM DC.

AC induction motors: You must first subtract the flux current from the total stator current to have motor torque proportional to current.

magnetizing current = flux current

flux current + torque current = total stator current


Ok I have been doing some research and talked to a few people, none of whom were electrical engineers (I can't seem to find one just lying around).  However, It seems if I build either circuit the pwm triac one or the switched capacitor (which seems a little easier).  

I would take a fan out of the box, remove the covers exposing the motor and the current control circuit.  Basically cut out the current circuit.  (snip snip unscrew break off gone).

Leaving me with the wires from the motor (and light if I wanted to get involved -- I have an led dimming system) but lets just do the motor just cleaning out everything else I would be left with the motor leads.

I would take the bare wires left and attach safe and strong connectors that matches my control circuit.

Mount my control circuit connect the motor leads, clean and safe everything up put the covers back on the fan and put the fan back in the box and send it to the end consumer.

If I can do this in less than 30 minutes per fan it works for my application.

I would only work with let's say the single phase motor suggested in an earlier post.  And in a perfect world I would only do a certain model of that motor or maybe small set of motor types that I have checked my control unit against and made safe.

My biggest problem is people want different colors and fan diameter and fan blade materials, look and color.  I don't want to get into the fan manufacturing business, more like the fan modification business.

I am going to build prototypes of both systems I think.  The pwm triac gives a small benefit in that the fan speed can be from like 10 -100% incrementally by like 2%.  I am not sure that is necessary I think a 4 speed fan is sufficient for most applications.  If this capacitor design is as simple as it looks and not detrimental to the motor I have a feeling that is the way to go.  (I haven't looked at costs yet though)

Anyhow if anyone wants to please let me know where the holes in my system are.  

Also I am guessing L1 and L2 in my capacitor design are the primary and secondary windings.  Which make it easy enough.

Thanks all



Holes in your system???? Are you really serious?  Are you going to warranty your system for some period of time? Have you talked to your insurance agent about extended liability insurance? Have you talked to your lawyer about your personal liability? All you want to do are very practical, but you need to protect yourself and family financially.

Have you considered the price you will charge? Will you be able to restore the fan to original condition?



I've considred the politics and safety regulations.  We are a manufacturing company we manufacture moveable louver outdoor patio systems we sell business to business.  We have an a/c to 24 volt system that we designed that is insured on the market now.  I have built a bridge that will be insured, that connects that system (up to 8 actuators for louver control) to the internet with led lighting control and electrical switches. (which may become optocouplers if they work as advertised).  I have everything on a patio handled except the ceiling fans.

All of this runs on my ios/andriod app that is in alpha testing as we speak.

I am trying to figure out how to include a 4 switch speed control system for a fan that I can control with the rf200p81 wifi chips currently used in installations.   

I am pretty sure I am going to build at least one (probably two) prototypes (triac and capacitor) and see if I can get it to safely work.

I could build the fans with motors and generic parts.  However people need variety in their fan selection.  We are just exploring the issue of modifying fans instead of building them from scratch. 

We could very easily decide not to do it...........(read my original post I was giving up)

I just need help and direction to study how this works while I build the prototypes

Thank you all

Especially Leo


The point I was trying to make is you are voiding the UL/CE rating of the fan. You could not sell you product in Oregon, and perhaps other states.



mtalent,  I apologize for this side discussion in you thread.


Again I'm having trouble understanding your point.  Perhaps my definitions are different than yours.  So below I've added my understanding of the terminology.

Definition of proportional

a :corresponding in size, degree, or intensity
b :having the same or a constant ratio.  Corresponding sides of similar triangles are proportional


Definition of associative property of mathematics:
The associative property states that you can add or multiply regardless of how the numbers are grouped. By 'grouped' we mean 'how you use parenthesis'. In other words, if you are adding or multiplying it does not matter where you put the parenthesis. Add some parenthesis any where you like!.


totalstatorcurrent = fluxcurrent + torquecurrent    (note: your terms not mine)

If we increase total current by 20%

totalstatorcurrent 1.2  = (fluxcurrent + torquecurrent) * 1.2

ergo: torque is proportional to total stator current (again your term)

The only way this could not be true is if fluxcurrent does not change with total current.

This assumes the magnetic structure is not near saturation.

I don't think this thread is the proper place for this discussion I suggest if you wish to pursue this you start another thread.


Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.


Podoy CBB61 Ceiling Fan Capacitor for NEW TECH 5 Wire 4.5uf+5uf+6uf 250VAC

Link to product on amazon

went looking for the capacitors was having trouble finding them.  However I found the above setup that appears to have the capacitors built it.  I couldn't find one with the uF in the diagram but these say they are used for ceiling fans.

Will this one work on 110 though it ways 250vac is that a max.

How exactly would I switch between this setup it has two grey wires any help would be appreciated.

I hear you Paul, maybe if we get the control circuit ul approved it may not matter that I am using parts from another product as long as it's approved with a certain motor type and cfm load or fan blade diameter


You are talking about your circuit.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Can you tell us your electronic and hardware experience?

Basically cut out the current circuit.  (snip snip unscrew break off gone).
:o :o :o :o :o :o :o :o :o :o :o :o

Thanks.. Tom..  :o
Everything runs on smoke, let the smoke out, it stops running....


This is the circuit I am trying to re-create is the one on the left (from post 6).

My plan is to build a prototype of this cirucuit using electronic switches that I control with a microcontroller.  And test it on a fan motor with a load similar to fan blades (or I'll use fan blades not sure yet).

What I really want is a way to control fan speed placed between fan and power without any modifications to the fan.  However, that apparently is not possible.

If proof of concept works we will have an electrical engineer inspect the parts used make recommendations as to how to do it correctly and safely and if what we need to do is feasible.  If it looks good get eagle files out the pcb manufacture and assembly and go from there.

Honestly I am not very confident in the feasibility of this and feel it probably isn't going to work.  But I get leeway in these kinds of things and if I want to build a prototype and see what happens I can.

Anyhow I am still having trouble finding the capacitor values from the diagram that are A/C compatible.  I bought one set of fan capacitors I indicated in a previous post.  But I am not sure if it will work the same as the circuit above (because of different valued capacitors).

I am sorry for my use of terms like snip, snip I was just trying to explain the theory, of striping a fan down to it's main parts (like mainly motor) and controlling it.  (trying to keep the aesthetics of the fan the same)

So I am still researching how the circuit will react with different valued capacitors, any help on that or where to get the values indicated in the diagram would be great



All I need to do is replace the mechanical switch in a fan with mine.  I am working with ul to see if that causes any problems.

I can say that this site was pretty much useless in figuring this out, all I got was you can't, it won't and a bunch of other crud.

What I needed was all you need to do is replace the mechanical switch with your mcu controlled one.

anyhow here is the schematic for my electronic switch.  the purple and brown wires are actually connectd to capacitors 5uf and 6uf.

if anyone has anything constructive I will one be surprised and be happy to listen



Motors designed for this sort of job have a highly skewed rotor pattern - so they can run at a lot of 'slip'. So by altering the phase and current by means of capacitors on the 2nd of the  orthogonal windings compared to the 1st ( directly across the mains) you can alter  the torque and hence speed against a 'soggy' load such as a fan.

Should be possible.  It won't be very efficient. And the PF will be awful - but who cares?



thanks Allen,

Yes I have heard alot about how this is not the best way to do this.  And actually earlier in this thread there was a description of a different way with optocoupler and triac.

I finally ended up buying a used fan and taking it apart.  Low and behold there was the capacitors connected right to the mechanical switch.  It surprises me that fan manufactures didn't come up with a better system.


thanks Allen,

Yes I have heard alot about how this is not the best way to do this.  And actually earlier in this thread there was a description of a different way with optocoupler and triac.

I finally ended up buying a used fan and taking it apart.  Low and behold there was the capacitors connected right to the mechanical switch.  It surprises me that fan manufactures didn't come up with a better system.
Price is everything! I bet you didn't buy a remote control version.



No remote fan remember I want an inexpensive fan I can easily convert to run on over my mqtt and be controlled by the app.  So I figured the mechanical switching type would be the best to convert.

A little help -- here is the mechanical switch

Here is the capacitor pack

Ok .....

the house power black wire goes to switch position L

Brown wire from capacitor 6uh to switch position 2.

Purple wire from capacitor 5uh to switch position 3

Gray wire left side of capacitor pack goes to switch position 1

The other Gray wire from left side of capacitor pack goes directly to reverse switch

Red wire from capacitor 4.5uh pack goes directly to motor.

Ok my thinking is that the gray wire going directly to the reverse switch eventually makes it's way to primary coil

Red wire is going from capacitor pack to secondary coil no switch

Now I am having some problems with the purple, brown, gray wires going to switch.  And how to include them in my electronic relay.

The second gray wire is not connected to a capacitor and there are two of them where would I connect this wire to my switches.  I was originally thinking that I would switch house power to the brown and purple wires but then how does that get to the secondary winding.

The three place switch has house power and the gray wire and the purple and brown going in.  I have been trying to find a switch wiring schematic but not much luck.

Maybe I connect the gray to the black and the purple to the brown (not likely but man I am killing myself here I don't understand the flow of the current through the caps pack).

I have two switches/relays in my setup which should work for this setup.  because my thinking is low is both switches off, medium is one switch activated and high is both switches activated.  When I cut the switch out I am going to have 4 wires and my switches allow 3 (so am I going to connect two of them together or am I wrong and I need another relay).

Any help would be appreciated thanks all


found this if it helps...

Most likely a capacitor needs to be in series between the incoming power and the motor winding. In the case of my fan, as described in the previous paragraph, this means connecting a capacitor in series between the black and gray wires. The speed switch will also be involved of course, since it will determine which capacitor(s) are connected between the black and gray wires.

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