SCR phase angle firing

I've done the phase control with analog and microcontroller. On the analog side I copied a concept from Ampex to use a cosine ramp rather than linear to get a linear power change. It compensates for the sinewave.

In the microcontroller you use a zero cross of the AC line into an interrupt to synchronize an internal counter. Count off the 'subdivisions' of the AC line to get your firing angle. This works very well and is not difficult, not to mention an excellent programming exercise. It also has the virtues of very low parts count and flexibility. I used the Motorola (now Freescale) 68HC05 and '08 families. I'm sure you could use 8051 family and PICs.

GG