Do you know what... I edited my original post - checked last night ...it/I hadn't posted!! Then I did a short follow up post last night (along the lines of "those resistances aren't recommendations but just to show the thought process...."). just checked in here again...that follow up post never made it either! I've also noticed that my R2 resistance value was out by a factor of 10! (must do better) ....anyone dabbling in 400V AC, must surely beconfident enough of what they're doing & not just roll with one dodgy/casual post!
To be clear...I was outlining the process behind dropping 400V AC down to 5V AC...not the actual resistors to use....(that's why I showed two examples stepping up in magnitude).... in practise I'd go for much higher resistors eg 395k & 5k @ 200V peak (cos the 400V AC anticipated is peak to peak) , that's about 500uA through the two resistors ....and a power dissipation of about 100mW.
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