I want to dim a lamp around 70W or more using arduino. I have found two ways for doing that. The first one is to make a circuit that "cuts" the sine wave and produce the dimming effect (link). The other way is to make a circuit that uses a PWM pin to dim a lamp (link). So what is the best solution and why? In my opinion the one with the PWM pin is better because it uses only 2 cables to send signal to the circuit and it is much easier in coding.
PWM or Phase Control Dimming
arduinodimmerlightpwm
Best Answer
Phase control for AC Mains dimming is old but proven technology. This is, of course, PWM control that just happens to be synchronized with the incoming AC Mains waveform.
That said, you can try using a non-synchronized PWM but you need to be aware that you may run into frequency beating problems. That is: if your PWM frequency is not harmonically related to the Ac Mains frequency, you may see the difference in frequency as a low-frequency beat. This will cause the lamp brightness to vary at a periodic rate.
I honestly don't know how well non-synchronized PWM will work. I hope that you try it and let us know how well it works.