[sdiy] Powerline LC filters etc.

[Harry Bissell]

you'll have to try them and see. If you really get 40db its better than nothing. You need to see what kind of voltage
drops you get as well.

btw if you do create ground loops, you will reduce the effectiveness of the filter and possibly mske the source/sink
currents unequal, making the core move toward saturation. 

It's rarely so 'off the shelf' :^)

Do you need to pass emissions testing ?  (boy i hope not, its a pita)

H^) harry




----- Original Message -----
From: Tom Bugs <admin at bugbrand.co.uk>
To: 'Synth-DIY DIY' <Synth-diy at dropmix.xs4all.nl>
Sent: Wed, 29 Feb 2012 11:07:02 -0500 (EST)
Subject: Re: [sdiy] Powerline LC filters etc.

PS - checking back to the datasheet I linked to yesterday: 
http://www.mouser.com/catalog/specsheets/Murata%20BNX%20Series.pdf
The BNX016 has 40dB insertion loss at 100kHz - and it is low profile so, 
fingers crossed, it may be useful for me.

On 29/02/2012 14:33, Harry Bissell wrote:
> I'm not sure I understood the original question. Are we talking about AC Power Line Filters,
> or common mode filters used on DC power system rails ?
>
> In either case, the usual use for these filters is to reduce the passage of EMI (RF) signals in or out
> of the system. Usually this protection exists for frequencies from the 10MHz and higher range, its rare
> to get down as low as 1MHz with any efficiency.
>
> If I got the original point, the use of an inductor (as part of a common mode choke) in the ground has
> several purposes. In the DC case, the return current to the supply cancels out the current from the supply,
> resulting in a nearly zero flux in the coil (so it will not saturate easily).
>
> This does have the downside that there is impedance in the ground line... OK if the circuit is an "island"
> but maybe not so good if the circuit needs to be connected to other items in use (such as other modules, effects,
> amplifiers etc).
>
> Its a very complex issue... what is good for one unit may totally screw up the rest of a larger system.
>
> Tom... what is the filter supposed to do for you ?  (then we can dive deeper :^)
>
>
> ----- Original Message -----
> From: Jeff Brown<guitaricon at verizon.net>
> To: 'Tom Bugs'<admin at bugbrand.co.uk>, 'Synth-DIY DIY'<Synth-diy at dropmix.xs4all.nl>
> Sent: Tue, 28 Feb 2012 20:15:01 -0500 (EST)
> Subject: Re: [sdiy] Powerline LC filters etc.
>
> Try searching for "power line filter".  One that I found:
>
> http://www.ecoca.ro/papers/09_ARtim991.pdf
>
> shows a basic LC filter on the 3rd page.  You can also just buy these - even
> ones built into a chassis mount female receptacle.
> They're also called "EMI filters".  Most medical electronic equipment that
> is mains powered has them.
>
> -Jeff
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Tom Bugs
> Sent: Tuesday, February 28, 2012 5:40 AM
> To: Synth-DIY DIY
> Subject: [sdiy] Powerline LC filters etc.
>
> I would like no learn more about using LC filters for power-line noise
> suppression. On this front, therefore, a couple of questions::
>
> - can anyone recommend a good source of info - a book or a particular
> site - google has got me a bit confused/overloaded
> - I've been looking at the Murata BNX devices -
> http://www.mouser.com/catalog/specsheets/Murata%20BNX%20Series.pdf --if
> you look at the BNX002-01, you see a schematic diagram (similar is used
> on several other devices).
> I am curious about i) having an inductor in the ground line and ii) how
> you may calculate suitable values for the caps&  inductors (as I say,
> linkage to a book/site with info on these areas would be fantastic too).
> Of course, these devices seem to be designed with some specific areas of
> importance (http://www.rapidonline.com/pdf/26-6010e.pdf mentions
> everything being aligned in the same direction) so perhaps it is best to
> use these parts 'off the shelf' rather than trying to DIY - but, still,
> I would love to understand better.
>
> Cheers for any pointers,
> Tom
>
>

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Harry Bissell & Nora Abdullah 4eva