Fan Dinmer using ATmega8A

Hello,

In this project we are trying to control the speed of the Ceiling Fan using ATmega8 as a micro-controller. Basically we are trying to develop a Fan dimmer with Traic and MOC3021.

We have already wrote a program for speed control of Fan but, we are facing following problems

- Pulsating waveform to a Traic resulting in a oscillation/vibration/moments of Fan.

- Fan makes noise at lower speeds.

OK few things to take care:
1. You cannot give a pulsating waveform to TRIAC as this is not a DC circuit where PWM will change output voltage
2. TRIAC should be fired only once after there is a zero cross
3. TRIAC goes off automatically at Zero cross
4. You only need to chop the AC signal that comes from the AC Mains so the output wavefom is the actual time when device is on.

Like this:


Now AC mains freq = 50Hz
Zero cross will occur every = 1/50/2 = 10ms approx

Let say you want to chop 50% of the wave then, after zero-cross wait for approx 5ms and then fire the TRIAC this will make sure output AC signal is active only half the time of input signal. This way you can create your steps. similarly for 10%: 1ms delay and then fire TRIAC.

Let us know if anymore questions.

[Topic moved to AVR Discussion Forum]

Mains fan motors are generally meant to only run at one speed.
You can only slow them down by cutting their power.
Running at the wrong speed can cause overheating.
Try it, but don't expect to get good control with this method.

For AC devices, power = area under the curve so if you chop the signal properly then there will be no flickering or humming noise. If you can share the details on how you're currently controlling the firing of triac maybe we can help you better.