PWM question

[everettdale]

I have the LOR CTB16PC controller, and I was wondering how it controls the light level in an AC string of lights? Do they use PWM or are they adjusting the voltage in some way. Or is there something else at play?

I tried to find this answer but wasn't sure how to search for it.

 

[David_AVD]

Phase angle control.

 

[TerryK]

The controller does adjust the voltage the string sees. A bit of research of SCR or Triac theory will give you a better understanding of controlling voltage (and indirectly, current) via on/off control of a AC waveform.

 

[Mark_M]

There's a few techniques LOR could be using for AC dimming effect.

Phase trailing edge or phase leading edge or 'phase control' (best of both leading/trailing).
Likely not sinewave dimming.


Take a look at: https://www.dmlights.com/help/lighting/different-methods-dimming/

White section is part of the sinewave that is switched to the lights, the Red and/or Blue section is cut off.
How much of the red/blue section is cut off is what produces the dimming effect.



A sine-wave dimming with high cycle rate PWM, like this, is a little more expensive to accomplish:

 

[David_AVD]

Those LOR AC controllers use leading edge phase angle control. Nothing fancy at all.