Re: Choosing a ferrite bead

Mike Noone wrote:
> "Anthony Fremont" <spam@xxxxxxxxxxxx> wrote in
> news:mCUwf.243$1J1.235@xxxxxxxxxxxxxxxxxxxx:
> > "Mike Noone" wrote:

> >> Hi - I was recently reccomended to use a ferrite bead to get rid of
> > noise
> >> on a very noisy supply line. I have never used a ferrite bead so am
> >> unfamiliar with their usage. The supply line is a 6VDC line and it is
> >> supplying a GPS module that consumes approximately 70ma. The noise is
> >> caused by 18 motors running on the same 6V line. I don't care about
> > the
> >> motors getting a noisy supply but I've been told I need to keep noise
> > under
> >> 100mV on the GPS supply. Can anybody tell me how to choose a ferrite
> > bead
> >> for this application? I don't have any measurements for just how
> >> noisy
> > this
> >> 6V line is as the board is still being designed! So what that in
> >> mind,
> > I'd
> >> like to error very far on the side of caution.
> >
> > Here's some decent information about using them:
> >
> > http://www.antennex.com/shack/Dec99/beads.htm
> >
> > I'm not sure how much they will help you though, since you're not
> > really talking about RF frequencies, but they may help tame the
> > spikes. Make sure you have bypass caps on your motor terminals and
> > use some bypass and filter caps near the GPS module.
> >
> >
>
> Oh I should have bypass caps on the motors? I thought bypass caps were
> only for things that were sensitive to large loads. Any idea how large
> of a bypass cap I should use? The motors peak at about 200ma at 6VDC.
> Thanks,
>
> -Mike

make sure theyre ceramic plate, not wound types.

Another approach is to put your gps supply through a diode and
reservoir cap. The cap function is obvious, half the noise is
eliminated by the cap staying at 5.4v when the noise is down-going
(cant think of a better word!) and positive going noise has to face the
diode resistance then the cap.


NT

.

Relevant Pages

  • Re: Choosing a ferrite bead
    ... >> supplying a GPS module that consumes approximately 70ma. ... The noise is ... >> caused by 18 motors running on the same 6V line. ... Oh I should have bypass caps on the motors? ...
    (sci.electronics.design)
  • Re: Choosing a ferrite bead
    ... >>> supplying a GPS module that consumes approximately 70ma. ... The noise is ... >>> caused by 18 motors running on the same 6V line. ... > Oh I should have bypass caps on the motors? ...
    (sci.electronics.design)
  • Re: Replace capacitors Part 2
    ... but separate issue to noise on the supply rail. ... We are talking about capacitor legs here - any induced hf wobbles are ... going to get damped by the cap anyway. ... Long leads are bodges to a greater or lesser extent, ...
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  • Re: Flyback transformer design confusion!!
    ... Fred Bartoli wrote: ... next you will be asserting that the change in energy stored in a cap is ... Ask lemonjuice what he thinks about amplifiers noise :-) ... Have you been snooping around peoples homes without low noise ...
    (sci.electronics.design)
  • Re: Low Frequency Mains Noise
    ... the meter needle all over the place one you try to see noise below 1mV. ... parallel to the last 100uF cap in the filter line up, ie, the filter cap ... Zeners placed across the second cap in an CRCRCRC filter can reduce LF ... the simplest shunt reg that isn't ...
    (rec.audio.tubes)