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PCB Layout AC Question
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admiralk:
My current project uses relays and I an not sure how to handle the AC part of the circuit. I am using 10A relays, which will change to 15A if I make a next version.

It was suggested that I cut my pours down to ~ 60 mil traces and have them on both the bottom and top layer. I am also concerned about the gap between traces, and if I should include the cutouts or not worry about it. The DC part still has some changes to be made to it. It is the AC part, on the right, that I an concerned with for now. I would really like to hear some opinions on how I have it and I could better handle it.
mdszy:
Looks very similar to a board I just did that involved 10A relays and AC stuff. See attached for the PCB I ended up using and that worked just fine.

I previously had a board that didn't have sufficient AC isolation, so the AC was coupling back into the circuit and causing my microcontroller to freak out, there was 500mVpp 60Hz AC all over the microcontroller's pins.

This board worked just fine, and the main concerns are thick enough traces for current, and excluding your ground plane from the AC area.

I don't think the slots are necessary, relays are already quite isolated internally so there don't need to be slots under them, in my opinion.

admiralk:
My ground plane is on the bottom layer, so it is farther away from the AC, so I should be good there.

It looks like a 60 mil trace would be fine, from your design, especially if I use both sides. That would also give me much more clearance.

I do need to double check the pin size on he relays. They are probably the smallest diameter of all the components, yet I have them as one of the biggest.
floobydust:
I would say the slots are not needed 1.9 mm is decent spacing.
The annular ring is looks small on all your pads. IPC for big ones is twice the hole size, so 1mm hole 2mm dia. pad. The relays need more, especially if 1oz copper.
The J1 connector pad holes look unequal and the relay coil too but maybe an illusion or rendering is doing that.

I would consider moving all the low voltage stuff over so you can have four mounting holes. Right now the one corner can bend down, especially when the connectors are screwed or wire torque, so the PCB could touch the chassis. The connector would be in front of a relay.
ULN2003 (5V) maybe get rid of 20 some discretes/resistors/diodes driving the relays, even though some outputs wasted.

Mains relay contacts arc a little and generate a burst of EMI, which is coupled to your logic from the relay coils. Usually a 0.01uF cap from GND to chassis to cover that, assuming a metal box and spacers.
MarkF:

--- Quote from: mdszy on July 01, 2019, 12:24:55 am ---Looks very similar to a board I just did that involved 10A relays and AC stuff. See attached for the PCB I ended up using and that worked just fine.

I previously had a board that didn't have sufficient AC isolation, so the AC was coupling back into the circuit and causing my microcontroller to freak out, there was 500mVpp 60Hz AC all over the microcontroller's pins.

This board worked just fine, and the main concerns are thick enough traces for current, and excluding your ground plane from the AC area.

I don't think the slots are necessary, relays are already quite isolated internally so there don't need to be slots under them, in my opinion.

--- End quote ---

I would propose a different routing with larger clearances.
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