[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: RE: Re: How do I get rid of noise spikes on my Power lines

From: Sandor Ajzenstat   sandorinterlog.com
Date: Mon, 16 Aug 2004 12:48:01 -0700

A! Sent via the Art & Robotics Group mailing list: arg-list@xxxxxxxxxxxxxxx
R! Use your "Reply All" to  reply to the list, "Reply" for private response
G!

Hi again Jess,

This is just a bit more detail on my experience with placing a 1uF nonpolar
cap across Signal and GND where it entered a circuit board.  As I mentioned
the cap effectively filtered out all data pulses as well as noise spikes.
The first thing I tried was to extend my high-going data pulse duty cycles
by 50 NOP instructions (my PIC was running at 40MHz).  This was not
sufficient because the cap still filtered it all out.  I then went right to
500 NOP instructions and this was sufficient, so I just left it at 500.  If
you're sending serial data as opposed to just discrete pulses like I was,
and you think there is a chance that noise pulses are getting onto your
Signal lines, then maybe part of your solution would be to reduce your baud
rate.

I should mention that after the capacitor conditioned my signal, it was
necessary to put the signal through a schmitt trigger to sharpen up the
transitions.

Take care,
Sandor




----- Original Message -----
From: "Bruce Cannon"
To: "Arg-List@Interaccess. Org" <arg-list@xxxxxxxxxxxxxxx>
Sent: Monday, August 16, 2004 11:22 AM
Subject: ARG: RE: Re: How do I get rid of noise spikes on my Power lines


> A! Sent via the Art & Robotics Group mailing list:
arg-list@xxxxxxxxxxxxxxx
> R! Use your "Reply All" to  reply to the list, "Reply" for private
response
> G!
>
> Great suggestions.  Another is instead of a multi-supply use a simple 12v
> supply, perhaps linear, and regulate down AFTER the long wire runs, at
each
> board, for sensitive electronics.  Fans etc. don't care about reliable
> voltage much.
>
> --Bruce
>
> PC switchers are fussy.  They have min current draw for each output else
> their outputs are not stable, sometimes not even on at all.  If you aren't
> meeting the mins with your lads, you might have to add dummy loads (big
> resister) to get the system stable.  I find generic PC supplies unsuitable
> for most low-current applications because of hassles like these.
>
>
>
> > -----Original Message-----
> > From: The ARG Mailing List On Behalf Of Sandor Ajzenstat
> > Sent: Monday, August 16, 2004 2:11 PM
> > To: jessica field; arg-list@xxxxxxxxxxxxxxx
> > Subject: ARG: Re: How do I get rid of noise spikes on my Power lines
> >
> >
> > A! Sent via the Art & Robotics Group mailing list:
> > arg-list@xxxxxxxxxxxxxxx
> > R! Use your "Reply All" to  reply to the list, "Reply" for
> > private response
> > G!
> >
> > Dear Jessica,
> >
> > I have had great luck in eliminating spikes using 1uF nonpolar
capacitors.
> > Everything I'm describing here is related to things I needed to do for
one
> > piece in order to get rid of intermittent spikes.  I would suggest
picking
> > up 10 or 15 of these 1uF nonpolar caps, as well as an assortment
> > of smaller
> > value nonpolar caps, and experimenting with them in various places.
> >
> > Step one.  I would certainly suggest placing one across the power
> > lines that
> > feed the fan  I would start by placing the cap as close as I can to the
> > actual fan inputs..  Also, I would place one across the DC power lines
> > wherever they enter any circuit board after running along a cable.
> > Experiment with them in other places too.
> >
> > Step two would be to ensure that for long cable runs that your
> > wire gauge is
> > sufficient.  Believe it or not I have found that to run 5 volts
> > DC along say
> > 20 feet or so I really need to use at least 18 (or prefferably 16) gauge
> > wire.  Otherwise the resistance which accumulates along the length of
the
> > conductor can weaken signal strength too much in relation to
> > spike strenght.
> > If you don't think wire gauge is an issue then skip this step and
possibly
> > return to it later if necessary.
> >
> > Step three.  After having done the above, I still had intermittent spike
> > problems, although they now occurred at different times.  I found that
> > placing a 1uF nonpolar cap across from Signal to GND where those wires
> > entered a circuit board, completely cleaned up absolutely every spike.
> > Unfortunately it also cleaned up all my data pulses too.  In order to
get
> > around this I substantially lengthened the duty cycle for all my
> > data pulses
> > until they were of a long enough duration to get past the cap.
> > To do this I
> > just used a whole bunch of NOP instructions.  This may not apply in your
> > case because all your signals may travel via wireless, and not via
copper
> > conductor.  Mind you, on a given circuit board spikes may be entering
your
> > signal lines, so it's worth thinking about. If your existing
> > spike durations
> > are very short in relation to your data transition durations then it
ought
> > to be possible to find the right value of cap to clean up spikes without
> > affecting the data transitions. This would take time and
experimentation.
> >
> > Step four.  When you're next at Supremetronics, use diagrams to
precisely
> > describe your problem to Kirk.  He's one of the younger guys behind the
> > counter there.  Kirk may be able to make recommendations or suggestions.
> >
> > Do not worry.  There is a solution.  The way to find it is by
> > patiently and
> > systematically trying things, and by keeping track of your
> > progress in note
> > form as you go.
> >
> > Generally, as I have done tests with various caps, I have left in
> > place the
> > ones I've already positioned, while adding other ones in other places.
A
> > complete solution may require numerous caps strategically placed in a
> > project.
> >
> > Good luck, but you won't need it.  You'll work it all out.
> > Sandor
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "jessica field" 
> > To: <arg-list@xxxxxxxxxxxxxxx>
> > Sent: Monday, August 16, 2004 6:20 AM
> > Subject: ARG: How do I get rid of noise spikes on my Power lines
> >
> >
> > > A! Sent via the Art & Robotics Group mailing list:
> > arg-list@xxxxxxxxxxxxxxx R! Use your "Reply All" to reply to the list,
> > "Reply" for private response G!
> > > I am using a PC power supply to power my electronic
> > application.  If I use
> > the +5 V output that does not run when the Power supply's fan is on, my
> > wireless network works perfectly.  As soon as I turn on the other
voltages
> > and the fan in the power supply, I get noise spikes on my +5 V
> > supply and I
> > have no wireless communication.  I need +12 V to run other
> > periferials so I
> > need to have my wireless working when the PC power supply's fan is on.
I
> > have designed my casing to have the PC power supply so I would very much
> > like to use it so I don't have to redesign everything.  I am on a
> > tight time
> > crunch to finish my project.
> > >
> > > I was wondering if anyone knew some good solutions.  I have
> > used a 220 nf
> > capacitor on the positive and negative line to try to clean up the
noise.
> > It helps a bit but I still need a better filtering system.  My
electronics
> > are on more than one board and my wireless transiever is
> > relatively far from
> > power supply and the Main board in wiring.
> > >
> > > Any help would be very appreciated.
> > >
> > > Jessica
> > >
> > >
> > >
>
> --------------------------------------------------------------------------
> > ------
> > > Don't just Search. Find! The new MSN Search: Fast. Clear. Easy. A! R!
> > messages saved at http://www.interaccess.org/arg/arg-list.html G!
> > unsubscribe/help requests to mailto:Majordomo@xxxxxxxxxxxxxxx
> > >
> >
> >
> > A!
> > R!      messages saved at http://www.interaccess.org/arg/arg-list.html
> > G!      unsubscribe/help requests to mailto:Majordomo@xxxxxxxxxxxxxxx
> >
> >
> >
>
>
>
> A!
> R!      messages saved at http://www.interaccess.org/arg/arg-list.html
> G!      unsubscribe/help requests to mailto:Majordomo@xxxxxxxxxxxxxxx


A!
R!      messages saved at http://www.interaccess.org/arg/arg-list.html
G!      unsubscribe/help requests to mailto:Majordomo@xxxxxxxxxxxxxxx