Re: [CAD_CAM_EDM_DRO] Re: L298 goes boom ( It's Fixed!- Yeah! )

Taus,
I also put a wirewound resistor in series from the main PS to drop
down it a little.
RichD

tauscnc wrote:

>
> Hey Afogassa,
> Man sounds like your really having trouble keeping them cool. I would
> like to see a pic of your homemade heat sink when you get the time. I
> have ran files (say 30 to 1 hour long) can checked the heat coming
> from the homemade heatsinks I have. There hot but not untouchable.
> The main ones that get REALLY hot is when I step the voltage down
> from 38v using a 7812 to 7805. I guess I am at the peak of the 7812
> as it says max voltage 35V but my VOM says my transformer in puting
> out 38V (after the brigde and cap).
>
> I connected the "Dreaded" switch that got me into this mess and its
> working! I now have AWO feature on the 3 axis board and a switch for
> it on my box :)
>
> later
> tauseef
>
> --- In CAD_CAM_EDM_DRO@y..., "afogassa" <afogassa@y...> wrote:
> > --- In CAD_CAM_EDM_DRO@y..., "tauscnc" <tauscnc@h...> wrote:
> > > Hey guys,
> > > well the day is almost over and I finally got my mill working!
> > well,
> > > 3 out of the 4 axis :) I got the stuff from mouser today and
> > quickly
> > > went to work. I put in the L298 and L297 into all axis and
> started
> > > checking the voltage switch and stuff on the camtronic board. As
> I
> > > was checking pin 1 on the L298, I slipped and the lead from the
> VOM
> > > touched pin 3 also. A little "Tick and a spark" and it was
> history
> > > for the Z axis L298 :( I did a quick check by plugging in the
> > stepper
> > > (No Power) and it was very gritty :(
> > >
> > > I then de-soldered the L298 from the single 4th axis, man what a
> > > project. Put that into the Z axis and checked everything. Held my
> > > breath and plugged it in, and a little "zap" at that L298 or so
> it
> > > seemed! O man! I quickly unplugged it and plugged in the stepper
> to
> > > see if it was gritty but to my surprise it wasn't...a good sign.
> > >
> > > I thought, I wondered and I asked what I got myself into :) I
> > plugged
> > > it in again (not knowing what to check) and nothing worked other
> > then
> > > the fan and the power and check LED did not come on!! After some
> > > thinking I found the 7812 burned out. Back to radio shack, and I
> > got
> > > a new 7812 and 7805 plus 2 of there beefier heatsinks to add to
> > mine
> > > homemade ones. Put everything back togeher and to make this very
> > long
> > > story short...IT WORKS!!!!!
> > >
> > > Since I only bought 4 L298, I have just removed the 4th axis as I
> > > really don't use it. I don't think having 4 drivers is of any use
> > to
> > > a hobbiest as we don't have/ can't afford 4D converting programs,
> > as
> > > I learn more.
> > >
> > > I plan to get another single unit from Dan, get one L298 from him
> > to
> > > fix the "4th axis" and use those 2 on the lathe. Not much for cnc
> > but
> > > more so I don't have to crank the handles so much :)
> > >
> > > It's still working, keep your fingers crossed!
> > >
> > > thanks for the help everyone
> > > tauseef
> >
> > I know how you feel, after replacing my l298 i have added a digital
> > termometer to the chip it self and I'm monitoring the temp on them,
> > it goes as high as 120f, with 1.3amps/fase. Ihave a custom made
> heat
> > sink with a aluminum plate and about 90 aluminum pins about 1" long
> > press fit at the aluminum plate and a big fan blowing across it.
> > I think I 'll need a better heat sink with about two small fans
> > direct bolted to the heat sink to keep it from over heating.
> > The problem is to get a big heat sink to fit in the board, if the
> > l298 were at the edge of the board it would be easyer.
>
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