[Al_The_Man]

which circuit you looking at AL. thanks for all the input on the thread, Im hoping to cut some pcb's early next week. im bummed my bits did not show up today

I found the code listing for that Pic 16C84 design and it does not have zero cross over switching.
Just a choice of either IGBT or Triac switching.
I thought by the print it may have had burst switching to avoid EMI?
Either way it uses phase angle control.
Al.

[KOC62]

Just discovered this thread. I've read most of it.

Electronic designs have such a wide range of doing similar things that there is no "best" circuit. Each design has good qualities and some not so good. Often a DIYer picks parts from their junk box and experiments away.

Regarding the zero crossing circuit, I have a preference for an H11AA1, which has two photo diodes inside, and add two 15K resistors to sample the AC line. This circuit would not require a transformer. However, it should be done by peiople who understand the danger of working with 120VAC (or 220VAC in some other countries). An experimenter may still need to add some additional componets for the zero crossing if AC noise is a problem.

Triac selection is somewhat power dependent. I'm thinking of a 16amp unit for my 120VAC source. I may experiment with some ST T1625T-8I that I got from Mouser. I tend to prefer the higher gate current types since I understand that the gate will be less sensative to noise. Again design choices with no "best" one. One may also choose a triac that has the package insulated from the AC line in case a heatsink is needed without getting shocks if you touched the heat sink while operating. Another design choice.

There are numerous manufacturers of triacs that provide design ideas, or application notes, to control motors, light, heaters, etc that you may get additional ideas of what to add. Since a motor will produce voltage spikes, some designers add a MOV (varistor) to clamp these spikes. The selection is AC line voltage dependent.