Limiting Mains current.

[Alex Tsekenis]

Your schematic looks OK. I think you can get away with increasing the value of R3 to a few kOhm unless your relay's coil draws something like 6W.

What did you have in mind with D9? Is that there for protection?

Finally, the zener diode at the gate of the IGBT. Maybe you dont need that if IC2 has internal clamping diodes to +12V.

 

[Riccardo1]

I think I will not use an isolation transformer then as it is bulky and expensive. All controls will also have plastic covers, and there will be no exposed metal parts. I think I'll earth the metal cases of the pots too just in case a cover gets broken off.

Oh yes, R3 is a bit low. Yes D9 is supposed to be there to keep out any negative transients, probably overkill but for the price of it, I thought I might as well.

The TC4428 data sheet says the pins are ESD protected but I couldn't see if the output was clamped to 12V. Again, possibly overkill, but I'd rather play it safe.

PS: D7 would be a UFB200FA40P rather than what is listed on the diagram.

Thanks for all the help guys!

 

[Alex Tsekenis]

OK, here is a picture of the lot. Check your PMs for more info.

View attachment 40777