Proximity of AC coil to snubber network

It doesn't much matter where you put the snubber. From an EMI standpoint, close to the relay coils is probably a little better than near the coil.

John

That snubber will do it's job fine there. If you're worried about noise then use a twisted pair to drive the coil. If the snubber is properly sized, it should do well in reducing RF radiation. Some use a shielded pair with the shield connected only at the driver end to ground.

Jamie

Nice, thanks Jamie. I hadn't thought about using twisted or coax, but that's a perfect idea to reduce any emissions that might want to propagate.

Jon

Actually, it will be most effective at the breaking-contact location.

RL

Oh, I guess I meant "relay contacts" not "relay coils." But close to the relay, anyhow.

John

All shields should be grounded at both ends, if not more often!

John

Cool, even better! Now that I think about it, that would explain why snubbers get mounted on silicon power devices instead of the transformers which they control.

Jon

What about ground loops?

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These are my opinions, not necessarily my employer's.  I hate spam.

Let'em happen, and deal with them. That's a lot better than having tens of volts of common-mode RF and spikes at the ungrounded end.

John

You shold try that at a radio or TV station. I had hum, and video getting into one audio console. I had to cut all the grounds at the patch bay that fed the inputs on the console to get rid of it. Early shieled audio cable had a bare braid, and any that were bundled and run inside racks had multiple ground points. There was over 10 volts of RF at the points where the sheilds were cut.

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You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

Oh really. Think about that for a moment.

Jamie

Really,, You've never heard of shielded grounds?

Jamie

No. What's a shielded ground?

John

Come on John, I know you have it in you!

Jamie..

I have no idea what that means.

John

I've heard of grounded shields. ;-)

Cheers! Rich

eo

Huh, most pro audio systems use balanced signals and are immune to ground loops.

The best way to keep RF out, is to ground the shields to the chassis at both ends. The balanced audio is not bothered by the resulting ground loops.

Mark

Broadcast isn't 'Pro Audio'. We used 'Pro Audio' gear for doorstops.

That's how the hum & noise was getting into the system. It WAS balanced 200 ohm & 600 ohm lines. It was eight feet from a TV transmitter, and under the station's AM antenna. Nine of the ten phone lines had the radio station's audio on the lines, as well. It took a complete rewire of the phone lines to eliminate that. I had to switch to

25 pair to multiple demarc points throughout the complex, with short drops to the phone jacks.

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You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

That's not true. Of the major pro audio intercom standards, one of three is balanced. Even with the one that is, there is no guarantee that there isn't several volts between systems.

But things can sure get hot!