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I have designed a pcb board (2 layer) that deals with high voltage 220VAC and it also converts it to 5VDC and 3.3VDC. So, because it is my first design and I deal with high voltage I want to be sure that the design its safe and I havent overlook something important. The board is meant to use the esp module to turn on and off two relays. Also, the board shape needs to be circular 50mm radius in order to fit where I want.
Here is the design:
Top side:
Bottom side:
To start with, if this is something you're going to install permanently in your home, it probably needs to meet the local building code requirements. In the USA, this would generally mean the NEC, which in turn would imply UL listing. Your jurisdiction may be different in the details, but the gist will be equivalent — if you don't meet this requirement, your homeowner's insurance might deny a claim, and you could face criminal prosecution in the event of property damage and/or personal injury.
But ignoring that for the moment, the first key requirement is isolation: can you draw a line across your schematic with all of the mains-connected items on one side and all of the low-voltage items on the other, with only components with suitable isolation crossing that line? Can you draw a similar line on your PCB, with at least an 8mm physical gap between the conductors? If not, then the design cannot be considered "safe" by most measures. This is just the first step in making sure that the end user cannot contact lethal voltages.
A second requirement is to mitigate the effects of component failures, such as making sure that short circuits don't allow excessive currents to flow. You have some fuses, etc. in your design, so you largely have this covered. However, you also need to make sure that you are protected against the kinds of surges that can occur on mains-connected equipment, such as those induced by nearby lightning strikes. This is another reason that isolation is important — including among the different conductors on the mains side of the isolation barrier you drew above. Spark gaps, MOVs, and other components can help prevent such surges from propagating into more delicate areas of your circuitry.
If you put a slotted air gap >= 2 mm between any AC line voltage and DC, it may meet some criteria for lightning 3kV dielectric insulation. But as it is , this design fails many DFM criteria and insulation breakdown tests. (Design for Mfg) There must be no sharp points between conductors of AC and DC at the nearest gap.
So back to the drawing board or go research design more before you try this.
The only way this could pass is if the assy were dried in an oven and conformally coated properly around all AC to increase the BDV from 500 V/mm to 5kV/mm after moving pads away.
