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I am making a PCB board with 4 relays controlled by a PIC microcontroller as shown. The board consists of components that are working on 5V DC and the relays that are connected to 110VAC. I had a few doubts regarding the ground plane:-

Q1. If I make a ground plane that covers the entire PCB, will the AC traces cause any problem in the working of the board?

Q2. Should I make a ground plane on the entire board or just for the DC portion of the board? Which will be better?

My PCB so far

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    \$\begingroup\$ My opinion only - Keep the Ground Plane away from the high voltage section. \$\endgroup\$ – Dwayne Reid Feb 23 '17 at 21:56
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    \$\begingroup\$ Mains freq is nowhere near high enough to cause those kinds of issues, it's not until you get into the millions of Hz that you even have to think about split ground planes. However it's a good idea to keep the ground plane away from the Mains voltage area for safety reasons, you want to be sure that even if the PCB gets scratched and dirty that the mains voltage can't arc over and jump the gap to the low voltage stuff (but that rule applies to any high voltage stuff, irrespective of whether it's AC, DC or RF). You might want to leave a pin unconnected between the mains and LV sides. \$\endgroup\$ – Sam Feb 23 '17 at 23:14
  • \$\begingroup\$ Will this PCB have a solder mask? \$\endgroup\$ – Wesley Lee Feb 23 '17 at 23:22
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    \$\begingroup\$ OP has a trace coming from the GND plane, to the bottom of the rectifier and both ends of the conectors. Even if he manages to keep the GND plane out of the AC side, he still has GND traces, cabling and connectors quite close to AC. \$\endgroup\$ – Wesley Lee Feb 23 '17 at 23:58
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    \$\begingroup\$ You forgot to put diodes in parallel to your relais coil. Your driver transistors will fail sooner or later. \$\endgroup\$ – Nils Pipenbrinck Feb 24 '17 at 8:09
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Definitely do not extend the ground plane into the mains area.

The relays are providing your safety isolation here. Draw a line (real or imaginary) across the middle of all the relays. Keep all low voltage tracking and components 'this' side of the line, keep all mains stuff 'that' side of the line. That will automatically ensure you maintain adequate clearances between the sides.

It looks like you have an unholy mix of low voltage and high voltage connections side by side in the same terminal block. Easy for channel identification. Perfect for lethal error. Have the control terminals and 24v one side. Have all the mains terminals the other side. Put the relays in the middle, keeping them apart. Line the control and output connectors up in the same order, if you want a nice visual channel identification.

On a board of this type, you do not need a ground plane at all. Far better to just track it.

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I think exiting grounding is enough. I advice to exclude 110v circuit from 24v circuit connector. it is good idea to have 2 different connectors for 24v circuits and 110v circuits. In addition, i think it is need to set protective diodes on relay coil.

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