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As known, it's not good to route noise sensitive signal traces under relay. Then what about ground pouring under the relay? Is it good or not?

diverger
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  • I believe this depends on the location on the board of noise sensitive ICs. – Vladimir Cravero Feb 22 '16 at 14:16
  • I know some noise may couple to the other ICs through the ground. Then if the ground can shiled some noise? – diverger Feb 22 '16 at 14:22
  • If your ground is being used by noise sensitive devices, then my initial reaction is to *not* pour under the relay; most electro-mechanical relays generate *large* amounts of noise. – Peter Smith Feb 22 '16 at 14:23
  • Then, what about if I've separated the relay driving circuit's ground from my noise sensitive circuit. That say, they have not common ground. – diverger Feb 22 '16 at 14:33

1 Answers1

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Henry Ott has written extensively on this subject. There is a nice 3-4 page writeup about how to include both noisy and sensitive circuits on the same board while sharing the same ground plane using "moats" and "bridges" to contain noise on the plane without having to maintain two split planes. You can find that paper here.

His writing in that paper is specific to mixed analog and digital design, but you could apply it to this case of a relay on board with your other circuits. I've done this with some of my mixed signal (audio) boards with relays near the audio traces and this method worked really, really well.

Some clamping diodes near the relay to catch coil closure/release noise would be a good idea too if you don't have them already. You can read more about that on this thread.

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mhilden
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