Transformerless power supply: Can I lose the opto?
I'm sketching out a circuit that uses a resistive power supply as described in Microchip's Application Note 954.
One of the advantages of a transformerless power supply is that it eliminates one of the most expensive parts on the board: the transformer. One of the big disadvantages is that even the low-voltage parts are referenced to mains voltage, which could be lethal if you touch a part while the doohickey is running.
My circuit would be a DMX node with integrated SSR's. As I looked at my schematic, with the traditional SSR circuit as the output, I started asking myself... why do I have the optoisolators in there? If my low-voltage stuff is going to be referenced to mains voltage, would it be possible to trigger the TRIAC directly from an I/O pin of the PIC chip? That would save on parts count, too!
There sure as hell *are* user-serviceable parts inside!