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Experimentonomen quits class d

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Experimentonomen

Mon Jun 24 2013, 05:43PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

I found a highly interesting video about EMC:

And after watching said video, this is my conclusion of the problems i have:

Avalanche

Mon Jun 24 2013, 10:09PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Experimentonomen wrote ...

I think im gonna take all of the yet unpopulated boards, pack them in a cardboard box with some crumpled up news paper, fo out somewhere where theres no ppl around and burn the crap.

The boards for the all discrete version arrived today but as they have the power traces running on either side of the board, they will surely be the same transmitters as the ic based version i have the EMI problems with, so im not even gonna bother wasting components to try one out.

don't burn the boards, use them! The whole point of development work is to end up with a load of heavily modded and chopped up boards! In the process, you'll learn loads about good layout technique, and get the chance to experiment with different components and configurations hands on - rather than trying to figure out everything as you're laying out the board.

If I were you, grab a board and populate it then cut up the grounding and re-arrange it with copper tape, bits of wire, whatever it takes, to minimise your loop areas. Take the chance to investigate what's radiating and why, try different inductors/filtering etc and make gradual improvements. Once you have a bodged to hell board that works, you can think about putting those changes onto a new PCB layout.

If you want some inspiration, I can post some amusing pics of boards from work - of some real commercial products that have gone this way. First, second, boards always bring up new problems - my first one had 5v shorted to ground

Experimentonomen

Mon Jun 24 2013, 10:35PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

I guess i could take one of the modules already assambled, cut up one of the rail traces and bodgewire it up similar to the latest layout and see if theres any change what so ever.

Latest layout:

Steve Conner

Tue Jun 25 2013, 11:31AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yeah do that, you can easily reroute traces with pieces of wire, tack on ceramic caps and so on.

Experimentonomen

Tue Jun 25 2013, 04:46PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

I did an Avalanche:

Experimentonomen

Tue Jun 25 2013, 05:52PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

And just as expected, it did NOTHING, module is still aAM transmitter!! :(

Avalanche

Tue Jun 25 2013, 10:14PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Is there any improvement, or is it worse? and by how much?

This sort of thing won't be a case of suddenly 'solved it', I think before getting too stuck in you need to do two things - first establish how you are going to 'measure' the unwanted emissions as you're making changes on the board (could just be, say, a radio 2 meters away for making comparisons). Secondly, set yourself a realistic goal for what you're going to accept as final.

You won't get the emissions down to zero when you're only a couple of harmonics away from fundamental, on something that is switching, and especially without any kind of EMC enclosure. You can only minimise it and know where to stop!

I'm definitely no expert on EMC, but I've been lurking somewhere in the background on a couple of totally separate occasions now, where there was a lot of last minute panic to try and avoid paying for yet another day of EMC consultancy! I'll try and dig out a document someone at work gave me with some good board layout tips for EMC.

Stick at it

Conundrum

Wed Jun 26 2013, 05:21AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Put the boards in a picture frame and sell on Ebay as "Electronics Art" with a certificate of authenticity.

Avalanche

Wed Jun 26 2013, 07:26AM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

here's the document on layout tips
]pcb_design_guidelines_for_reduced_emi.pdf[/file]

Experimentonomen

Wed Jun 26 2013, 05:45PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

Modded the layout slightly moore:

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