[sdiy] anyone tried this SMPSU?

Brian Willoughby brianw at audiobanshee.com
Thu Feb 18 20:12:07 CET 2021


On Feb 17, 2021, at 06:43, ColinMuirDorward wrote:
> Conductive shielding is something I've never implemented, great idea to fab PCB for the job, I'll give this a go. I thought a conductive shield would need to be grounded, how can it do anything if it's just a floating piece of metal? Well I have seen people with tinfoil hats in the movies.

Fields are mysterious to me, so I do not have any definitive answers.

For one thing, though, ground is relative. 0V for one circuit might be 5V for another. It depends upon your reference, and even Earth is not the same potential at all points. So, in that sense, I believe that grounding a metal plate is no better than tying it to 5V DC, or some other DC power rail - provided there isn't a lot of noise on that rail - because in each case it's a steady voltage.

For another thing, I imagine that the fields hit the conductive shield and are "shorted out" in a way that stops the field from passing through, or at least heavily attenuates it. I'm imagining the different parts of the field fighting each other to induce a current in the shield, and thus canceling each other out (to some degree). Then again, I've already mentioned that I do not have a full understanding of fields. I might not have even considered this if I hadn't noticed the floating plate in the intellijel case above their power supply.

I'm hoping someone will pipe up and describe what happens when a field intersects a grounded PCB plane; or a plane held at some other constant potential; or a copper plane that's technically floating but still conducting really well within its bounds.

Brian





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