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Re: [Electronics_101] Re: Crystals and oscilators and such - pic

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  • Roy J. Tellason
    ... Yeah, I know about them. ... Maybe they put one in there to keep stuff from getting to the logic? ... Or maybe it s to keep other noise in the environment
    Message 1 of 32 , May 1, 2005
      On Saturday 30 April 2005 03:06 pm, Dave Mucha wrote:
      > > > EMIGUARD product.
      > > >
      > > > Ferrite cores on both legs and a varistor mixed in there
      > > > somewhere.
      >
      > > Varistor?
      >
      > The varistor is a surge protection device that is connected directly
      > across the AC input.
      >
      > This would be a clamping device. They are common in the cheap power
      > strips you buy.

      Yeah, I know about them.

      > Not sure where it would have a use here though.

      Maybe they put one in there to keep stuff from getting to the logic?

      > > You miss the point, though. This sort of thing started showing up
      > > all over the place (along with ferrite beads and lots of other filtering)
      > > when noise emitted by various bits of digital electronics started to
      > > become a problem with regard to interfering with radio and tv
      > > communications. This isn't so much to protect the circuitry that's in the
      > > box as it is to keep those really sharp transitions put out by the chips
      > > in the box from getting out, and causing interference.
      > >
      > > This is also why so many keyboard and mouse and monitor cables have
      > > a fat spot where there's a large ferrite bead included in the cable.
      > >
      > > Thanks to the FCC for all that sort of thing...
      >
      > There are two of thses puppies on the main sensing line that reads
      > the analogue voltage of the machine after a voltage difiver and
      > filter. that divider and filter are external so one would not expect
      > a huge amount of noise in this panel. better safe than sorry thought.

      Or maybe it's to keep other noise in the environment from getting in...

      Hard for me to say without looking at the unit, or a schematic of it.

      > As for noise eneraged from the circuit, the most crude stepper motor
      > driver will have orders of magnitude greater generated noise. This
      > circuit is only to monitor if the parameters are out, then tell which
      > way to move to get it back.

      Ok.

      > I have not pulled one of the components as it is a customers board
      > and it does not appear that the problem is in the area of these parts.

      You could get some idea if our guesses were close by just measuring across one
      of them without pulling it. If it's >10 ohms, or close to that, then it's
      probably what we're talking about here.

      > The power supply is +12/-12 to the LM324, and I think the op-amp is
      > fine.

      Easy enough to verify. Put your meter on an output, then short both inputs
      with a small screwdriver (most all circuits have enough resistors in there to
      make this not be a problem). The output should go to zero for bipolar
      supplies. Most common op amp failure I run across all the time is a short to
      one of the supply rails, most commonly the negative one in my experience.

      > It appears to be the relay and not the logic. the realy is also
      > powered thru one of these chips, but I think the relay itself is bad.

      Driven by one of the op amps, by any chance?
    • Dave Mucha
      After a couple e-mails with the engineering department, they think it might be a capacitor. link to data sheets http://tinyurl.com/duayq The equivalent circuit
      Message 32 of 32 , May 4, 2005
        After a couple e-mails with the engineering department, they think it
        might be a capacitor.

        link to data sheets
        http://tinyurl.com/duayq

        The equivalent circuit shows the two outter legs as being inductors
        with a non polarized capacitor in the center.

        Dave









        --- In Electronics_101@yahoogroups.com, "Stefan Trethan"
        <stefan_trethan@g...> wrote:
        > On Fri, 29 Apr 2005 20:49:07 -0000, Dave Mucha <dave_mucha@y...>
        > wrote:
        >
        > >
        > > Op's files sections, last item zzz-resonator
        > > Dave
        >
        >
        > That's really looking like one of those resonator buggers.. maybe a
        > filter..
        > You poke it with probes already?
        >
        > look here:
        > <http://hem.passagen.se/communication/ceramic.html>
        > that is the same MFG logo...
        >
        > ST
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