Great Scott's trailing edge dimmer circuit, DC Gnd conneciton to AC Mains

[jwhitmore]

I'm looking at this youtube video [1] and the circuit detailed in it. I've attached the screenshot of the schematic.

It's an interesting circuit, but as someone who has worked almost exclusively in DC circuitry I find the sub-circuit in the lower right a bit concerning. The mains AC is switched through the two IRF840 MOSFETs but there is a connection from between the two sources to Ground of the DC Circuitry.  OK so I assume that if there is no connection between the DC Ground and the AC Earth so everything should work just fine but it seems like a mistake could easily happen measuring a voltage relative to Earth.

I was thinking of using a logic level MOSFET [2], but even then instead of using a uC to control the gates, of the MOSFETs, I was thinking to just connect 5V DC between source and gate from a bench top power supply. Then given the mains voltage connected to DC Ground I'd be afraid of blowing up that piece of equipment. I guess DC ground is just riding the sine wave of the AC Mains and so long as it's isolated everything should work, but should I be worried about my bench top power supply? Again so long as I don't plug into 'Earth' connection everything should work. Might be better sacrificing a uC that's easier to replace if this does go wrong.

[1] https://youtu.be/BhQWOv10Oag
[2] http://www.farnell.com/datasheets/2284028.pdf

[DannyTheGhost]

Each time I look on this circuit I see more mistakes, even potentially lethal ones. If I were you, I would not try to build it.
Or it's unfinished circuit, who knows.
Optocoupler, which is driving MOSFETs, does not perform its function - isolation. Even if you supply right-side (with phototransistor) with separate isolated power supply, it still does not include 'turn-off' function for switches, only that 10k pull-down resistor can actually close them, which is bad for transistors.
Returning to your question, if you dare to build it, do not connect anything earthed to it.

[jwhitmore]

Thanks for your answer. I'll leave that one and maybe keep an eye out.