Hi all,
I am hoping to control the speed of a ceiling fan using a mobile app. I have been researching using pwm and a triac but everyone seems to say it isn't the best way to go and that the fan motor will be damaged and fail sooner than if it had been controlled differently.
It seems a Potentiometer is a variable resistor and from what I have read a lot of speed controls are just a set of different size resistors.
Has anyone heard of using a digital Potentiometer
Thanks
Mark
I think you will find that most digital potentiometers need a 5V (or lower) supply, and that the terminals of the potentiometer can only be connected to voltages between the supply and ground.
This will rule out their use in typical mains powered triac circuits.
Makes perfect sense..... Oh well
I think I am giving up on controlling fan speed, it seems that it's just not possible with pwm. I even tried looking up something pre-built that I could buy and use pwm to control it but no luck.
I did find this ........
A/C motor speed controller for hvac
it's $29 but I can't tell if it would be good for a ceiling fan
Anyhow thanks
Mark
Several years ago I had to replace the switch on a manual three-speed fan/light fixture. While it was apart, I was surprised to see the speeds were reduced by inserting different valued AC capacitors in series with the AC powering the fan motor.
Paul
Don't overlook this note about the hvac controller:
CAUTION – SmartFan Nimbus is designed for OEMs (Original Equipment Manufacturers) and is not intended for end-user or after-market applications. The Nimbus should only be used with compatible induction motors (Permanent Split Capacitor (PSC) or Shaded Pole) that are approved by the motor manufacturer for TRIAC (voltage) control. Attempting to control a fan or motor that is not compatible could cause excessive heating and/or permanent damage to the motor.
Fully adjustable speed ceiling fans are not common, they are usually two or three speed devices operating by way of switched capacitor reduced voltage motors. Trying to run them phase angle (triac) controlled will usually result in releasing the motors magic smoke installed at the factory.
If this were my project, I'd just buy a wifi-enabled fan...
HI,
Essentially a simple ceiling fan motor is a torque motor. The typical 3 speed motor is controlled by different capacitors in different configurations (as mentioned previously). You can verify this by removing the fan blades, then trying the 3 different speeds. You will find they will all result in a the same high speed, as there is not significant torque required. All the above is probably useless but possibly interesting information.
I know simple (i.e. no electronics) fan motors can be controlled by a triac dimmer. Most dimmer mfg make special dimmers for fans. These dimmers are "tuned" for inductive loads with the goal to reduce audible noise. Again probably not helpful unless you want to control a dimmer knob with a servo motor.
You could look into Levitor Model# DDF01-BLZ. It is a bluetooth fan controller. The only issue is that it is $50 at Home Depot and does not use an arduino (which you may or may not care about).
Good luck
SW1 SW2 SW3 Speed
Off Off Off Off
On Off Off Low
Off On Off Medium
Off Off On High
so this doesn't look all that difficult to build (is it ?????).
It says three switches which I am thinking I can control with these
Let me know and thanks for your help so far
I don't really need anything more than 3 speeds. I work for a patio manufacture and we are completing an app that controls lighting and the movable louvers and we thought if we could control fan speed that would just be one more thing.....
so a small device added between the fan and power with the fans original speed control set to high. So can I create my own capacitor control system with electronic switches
Or here is a ceiling fan capacitor with what appears to be two levels
The fan might not like being powered without any cap connected.
Leave the low speed cap always connected, and switch two additional caps in circuit (four speeds possible).
If you also want on/off, then use a relay in series with the fuse.
Leo..
Leo you old dog (or young) you, I am so happy to hear from you......
(I was ready to give up on this one)
So four settings is perfectly fine I am going to try to figure out exactly what you mean. However it sounds possible that is awsome news (I hate to give up).
My leo translator is coming online what you mean is the switch settings that were all off, off, off to turn the fan off was a bad idea.
Instead sw1 will not be a switch but always connected.
then the other two switches will be used to create 3 other settings above low.
just from my math classes classes 2 bits gives me 2^2 or four options.
it seems that first option 00 (sw2 open, sw3 open) is going to be low. (low)
then our second option 10 (sw2 closed, sw3 open) is going to be next level (low-mid)
then our third option 01 (sw2 open, sw3 closed) is going to be next level (mid)
and our final option 11 (sw2 closed, sw3 closed) is going to be final level (high)
then we put a switch in between house power and the fuse (or after fuse not sure) for on off.
Remember mark isn't the best with electricity diagrams but I am guessing f1 is the fuse, now I am not sure what L1 and L2 are maybe coils (I think) not sure what that is ...... they look like the devices in the switches I use that get powered to make the switch close
Now I am going to try to build a proto type this is the BOM I am thinking of
2 - of the above switches that I can activate with 3.3v
1 - 1.5 uF capacitor that is rated for the current
1 - 2.5 uF capacitor that is rated for the current
1 - 4.0 uF capacitor that is rated for the current
2 of the coil things I need help knowing what they are ......Please
1 fuse block
2 - two wire terminals (in/out of system)
I know you hate these long stories Leo, but we have the diagram I am just trying to re-create it.
I don't know what the round circle thing next to l1, l2 maybe that indicates the motor
Anyhow thanks for all the help
Mark
my dad Use to be the distributor in this area for hunters ceiling fans, He also carried the variable speed control circuits for these fans. They used a phase chopping circuit, to control the speed. Doing a quick search on the Internet I came up with this document.
although I do not know how accurate this information is, it is a starting point.
Hope this helps.
What I really want is something I can build that I can place between the power for the fan and house power. I need to be able to make 200 of these things. I have to decide if it is possible and worth it. However I found this stuff very interesting so I thought I would add my perception of how things are working (wrong probably)
4.2 Rectifier and Transformer
Ok this seems to explain the connection to the motor in my mind there must be terminal with three leads (either wires of screw terminal)
You connect the ground of the motor to the pcb.
Connect the two cables of the of the secondary winding to the brige on the board.
Connect the positive side of the bridge to GND with a 10K resister --- I've seen this before used to pull a pin down on a mosfet. That was on the negative side though, not sure why it is done here.
negative of bridge to ground makes sense.
I have an oscilloscope but I have never used it. (inherited it). I am guessing if you know what your doing this step is pretty easy
4.3 Connection from Rectifier to Board
Optocouplers (MOCs) are used to transmit signals between circuits that do not share a power source.
MOCs have a LED and a sensor inside. If the led is turned on, it activates the sensor and lets the current
flow.
This circuit is used to isolate signal circuitry from transients generated or transmitted by power supply and
high-current control circuits.
I really like the sound of this thing (I am buying one and a triac just for fun). So this translates from the pwm to triac I am guessing to control somekind of undesirable property of the triac.
I want to connect a 3.3v gpio/pwm pin off my synapses rf200p81 here to the bridge and remove the on board pwm.
It seems like it might be fun to buy a fan and control it with my app. I would have to be able to modify the fan in less than 15 minutes to be viable. I need to build something that can be easily added to the fan out of the box and the before adding power. I was hoping the capacitor idea would work but I haven't heard from Leo and I am not sure how the L1 and L2 work and what they are for and I am probably supposed to know.
Anyhow thanks for the input so far
We live to fight another day
mtalent,
You will find different motors have different capacitor configurations. Usually one of the 2 phase windings is powered by the line,however I have seen where at one of the speeds both phases are fed though capacitors. A google search will show a number of motor/capacitor/switch combinations.
BTW the capacitors form a (mostly) lossless AV voltage divider. The smaller the capacitor value, the less energy makes it to the winging. And although its been a long time since I looked at multipole 2 phase motors, I believe the phase shift adds to the reduction in torque as well.
Keep in mind, motors work on current, not voltage. The torque created is directly proportional to current though the windings.
Good luck
The torque created is directly proportional to current though the windings.
Way too broad of a statement. In some motors, yes. Some may be a maybe. In others, in no way is that factual. Case in point are small AC induction motors, they can require magnetizing currents in excess of 50% of the total current in the stator(s).
@ avr_fred
I'm sorry, I'm not sure what you are trying to say. In all motors I am aware, torque is proportional to flux and flux is proportional to current. I'm not sure I understand your example of an AC induction motor, is not the torque proportional to the flux. I did not suggest it was a 1:1 proportion but for the OP I was trying to communicate that the capacitors were essentially reducing the current to the motor.
John
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
Mark
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?
Paul
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.
Paul