Unfortunately it is not possible to use PWM to control the firing angle.
To properly control the firing angle you need a zero crossing detection and then compute the time lag until the SCR/TRIAC is fired.
The Fx2424 and Fx1616-BA and any SmartTILE-Fx based custom-made PLC support such built-in capability.
Please refer Chapter 18 (light Dimmer Control) of the Fx2424 User Manual for details.
You can download any user manuals from:
http://www.triplc.com/documentations.htmThank you.