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PCB shielding questions / CE approval — Parallax Forums

PCB shielding questions / CE approval

Zap-oZap-o Posts: 452
edited 2011-06-29 10:26 in General Discussion
I have a PCB that I am designing that must pass CE. I was wondering about PCB Board level shielding. Do you connect these shields to chassis ground, digital ground or analog ground? I assume chassis ground but that is my best shot at it. I simply never put a chassis ground on my PCBs so this would be something new.

Also how do you know if you need a board shield (Faraday cage)? I am using the propeller and some sensitive sensors and so far my prototype runs exceptional. Of course CE testing will submit high freq radiation to the unit so you can see why I am leaning towards PCB shielding.

Another issue, If I do in fact need shielding what parts do I need to shield? The entire board? The sensor measuring ICs the propeller?
A link to look at PCB shielding http://www.3gmetalworx.com/products/gallery.php?lang=en
Thanks for reading....

Comments

  • LeonLeon Posts: 7,620
    edited 2011-06-29 08:23
    You don't need shielding, I've worked on systems that were inside plastic enclosures. The hardware and PCBs were designed very carefully, of course, and the only problem we had with my first design was a VHF emission from an RS-232 cable which was detected in pre-testing, which was easily fixed with some filters.
  • Zap-oZap-o Posts: 452
    edited 2011-06-29 08:33
    Thanks Leon, but why?

    Cell phones have shielding, digital picture frames, monitors, computers all have shielding why would I not need it?

    I am intending on using a plastic case with a metal front and rear panel, not that that will mater but just for clarity.
  • LeonLeon Posts: 7,620
    edited 2011-06-29 08:50
    It depends on the design, Some need shielding, some don't. Mobile phones, for instance, have a transmitter and a receiver in close proximity, operating at the same time. We used a six-layer PCB which provided very good shielding. Consumer products often use double-sided boards and might need additional shielding because of the emissions.
  • Zap-oZap-o Posts: 452
    edited 2011-06-29 08:58
    Is there a book on this? I searched wiki and its not enough information.

    Also chassis ground or digital ground?
  • LeonLeon Posts: 7,620
    edited 2011-06-29 09:00
    There should be plenty of books on EMC. Most of it comes down to good engineering and common-sense. You also need to study the regulations.
  • bill190bill190 Posts: 769
    edited 2011-06-29 10:26
    Shielding would be to keep outside signals from getting in and causing trouble with sensitive electronics. Or to prevent signals from getting out and causing trouble with other electronic gizmos like a TV or radio.

    Electrical safety and to keep people or animals from being electrocuited, that is a different thing. Called grounding or earthing or double insulated. Here is a bit on this...
    (I don't know if this applies to CE?)
    http://en.wikipedia.org/wiki/Appliance_classes
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