I am currently designing a PCB for a project including PID-control of a heater. The heater runs on mains (220V) and is controlled using zero-crossing switching to regulate the power and minimize EMI and THD. I already designed multiple PCBs , also ones with mains, but never low and high voltages on the same board. By now I have e prototype-design, where I made the following safety considerations:
- strict separation (HV,leftside - LV, right side, see line on top silk layer)
- connection HV-LV only via optotransistor/-triac (U1 and U2) and a switching converter U6 including a isolation transformer
- further protection with MOV(R6), fuse (F1) and use of a snubberless triac Q1
- copper planes of LV part start only after the last everything is converted to LV
Since I do not really have any space constraints I designed everythig with a lot of clearence (grid is 1mm) and used 2mm traces for the AC-powerlines. The PCB is then mounted in a metal box connected to PE or in one out of isolation material. My main concern is that there are three JST plugs on the LV side (U4,7,8) that connect to rotary encoders, screens,etc, that are accessible to the user. While I am confident about the isolation on the PCB I still wanted to get second takes on the design, especially regarding the connections to the user-accesible features. Are there additional considerations to make in this case?
Any feedback regarding any part of the design is appreciated!