Proximity of AC coil to snubber network

I have a contactor with an AC coil, controlled by a small SPDT relay, and I
have the need for a snubber to reduce kickback when the relay opens.

It would greatly simplify things if I were able to mount the snubber network
on the board with the relay, which is a few feet from the AC coil on the
contactor.

I do realize that having the snubber network seperated from the AC coil by a
few feet is going to have the wires acting as little antennae, but for the
purposes of protecting the contacts on the little relay, will it be fine?

Thanks,

Jon

 

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

 

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

 

Oh really. Think about that for a moment.

Jamie

 

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

Jamie

 

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


Jamie..

 

No. What's a shielded ground?[/QUOTE]

I've heard of grounded shields. ;-)

Cheers!
Rich

 

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!

 

I find it hard to believe to that none has ever used coax or the
like cable as a ground leg.

The end that is attached to the ground source has both the shield
and center conductor combined. On the other end for the device that
wants the ground with out the noise with it, you use only the center
conductor and tape off the shield as close to the device as possible.

In the past, I've used RG8/213 type cable from a good out side ground
source, and led them up to the entrances of the shack/house with a metal
plate that had a coax female connector on it where we would attach this
coax. On the inside, you simply use the center conductor only..

This same is done noisy environments to reduce noise from traveling
along the ground legs and along the shielded signal wires.


Jamie