Re: L298 goes boom

hey rich,
I have not check the diodes to see if one/several are burned out.
Again, the whole thing was running just fine untill I connected J4 to
J8 and then a switch...NEVER a problem since then.
I will see how a diode is checked to see if its burned out.

thanks
tauseef

--- In CAD_CAM_EDM_DRO@y..., RichD <cmsteam@s...> wrote:
> Taus,
> One little bit more.
> Those big super high speed diodes that Dan specifies and is very
> explicit about insertion direction, have you checked them?
> Best done with the L298 out and motors pulled off.
> These diodes are the protection to snuff (limit) back EMF and
> "accidental" disconnects that produce high voltages, but they are
not
> absolutely guaranteed to save you everytime you abuse the rules.
> Any baddies or mistakes here will destroy drivers everytime.
> I have never lost an L298 without also having to change the L297.
> RichD
>
> tauscnc wrote:
> >
> > Hey,
> > well I don't know enough about electronics or what how EMF works.
I
> > do know what if I unplug a running fan from my 110V house outlet
> > there is a spark due to the difference in current etc. I assume
this
> > is the same thing that occurs if a stepper is at idle (still on)
or
> > running (still on).
> >
> > I look at it this way, Dan makes the boards, he designes the
boards,
> > he knows what he is doing, HE says NOT to disconnect a stepper
when
> > the power is on (as every other place I have seen), I figure heck
who
> > am I to disagree, hes gotta know what he is doing. Besides, why
> > chance it, its not that hard to switch off the power.
> >
> > just my .02
> >
> > tauseef
> >
> > --- In CAD_CAM_EDM_DRO@y..., "exeric1" <exeric1@y...> wrote:
> > > Hoyt,
> > > It normally takes a lot to get me stirred up but you managed it.
> > > There is easily enough EMF generated when the magnetic field
> > > collapses to jump the gap as the contacts are disconnected. This
> > > forum is for "helping" people - not generating bad info that
will
> > be
> > > expensive and discouraging to the people on it. May as well not
> > have
> > > a forum if information like this gets disseminated.
> > >
> > > Eric
> > >
> > > --- In CAD_CAM_EDM_DRO@y..., bjammin@i... wrote:
> > > > At 10:57 AM 8/4/02 -0400, RichD wrote:
> > > > >You are quite wrong. Any inductance carrying current will
> > generate
> > > large
> > > > >voltages when disconnected as the flux field collapses.
> > > >
> > > > Not back EMF, by definition. Also, it's not able to affect
> > drivers,
> > > as it
> > > > doesn't occur until disconnected from them. BUT, if you take
> > power
> > > off
> > > > steppers when connected, there *will* be a magnetic field
> > collapse
> > > that
> > > > puts voltage on the drivers ... and nobody even you has
cautioned
> > us
> > > > against that! Therefore, you need to think these things thru a
> > bit
> > > more
> > > > before writing.
> > > >
> > > > Regards, Hoyt McKagen
> > > >
> > > >
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address
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