AC FAN Speed Control via Dimmer using Microcontroller

[saeed_pk]

Dear All,
I need to control the speed of common ceiling fan using a Triac/dimmer I know about a dimmer circuit but it uses a POT.
I want to design a digital dimmer which get some Analog Voltage/or PWM from MCU and control the speed
or please tell me any other way i can do this.

 

[pranam77]

For controlling AC and its load, you need to control the phase angle of the waveform. You may program a microcontroller which may control the phase angle iin reference to the Zero crossing detected by a section dedicated for it. The micro may drive an opto and that in turn may drive the gate of a triac. PWM works fine with DC
Cheers

 

[daviddlc]

If the dimmer uses a pot, another possibility is to use a digital pot controlled by the micro, but you need to isolate the microcontroller from AC levels.

 

[millwood]

wouldn't it be infinitely easier just to get a regular dimmer?

 

[deperkin]

controlling AC fan is very tricky business.

You do need a zero-crossing detector. I use a 1Mohm resistor straight into an interrupt Pin.

Getting the timing down is tricky though and I have not been perfectly sucessful.

Alot of it depends on what type of triac you use.

Lookup TB094 on the Microchip site: "Dimming AC Incandescent Lamps Using A PIC10F200"
this will get you started.

Using a light dimmer is not the best approach for an inductive load however.

Variable frequency is the better choice, but more complex.

Is the project for controlling a ceiling fan with a remote control or something??
you can buy those as well. Or if it is for a wall, that is even cheaper.

If it is just for learning purposes, I would warn you that it is not a simple task.

Another easy option is to use a 'motorized potentiometer' and drive it with the uC.

 

[asimov]

Why don't people refer to application notes by several companies they cover all these aspects(whats the point in reinventing a wheel). I am attaching the link for this application.

**broken link removed**

Asimov

 

[millwood]

Why don't people refer to application notes by several companies

why take the easy route when difficult ones exist?

 

[dr pepper]

I have never tried this with an ac power control circuit, however certain d to a Ic's can be used as a pot, so long as one end of the pot is grounded, the other track end connect to the d to a vref input, and the 'wiper' is the d to a output.
Using a proper pot ic is probably better.
If all of the pic circuit is well insualted then isolating the chip isnt totally necessary, so long as steps are taken to stop noise from latching up the chip.
This isnt reccomended though for a prototype esp if it was someone with limited experience.