RE: [CAD_CAM_EDM_DRO] L297/L298 board concern

Yes, I was just looking at the board and there's a connection for Vref and I
mistakenly left it unconnected. Just out of curiosity, what should Vref be
for what current? If it's unconnected, what would the current be?

Thanks again guys!

Gary

> -----Original Message-----
> From: James Cullins [mailto:jcullins@...]
> Sent: Friday, November 15, 2002 9:03 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] L297/L298 board concern
>
>
> I believe it limits the current during run as well.
> Jim
> ----- Original Message -----
> From: "Rose, Gary" <Gary.Rose@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Friday, November 15, 2002 7:46 AM
> Subject: RE: [CAD_CAM_EDM_DRO] L297/L298 board concern
>
>
> > Thanks for the good information on the Vref, I'm definitely
> going to look
> > into it.
> >
> > I'm not sure if that's my problem though. I was running
> the motor on the
> > bench using a clock generator and a power supply. The
> motor was turning
> > continuously, so I don't think the Vref circuit that lowers
> the current
> > after 100ms would even kick in there.
> >
> > I'm going to try lowering it anyway and see what I get,
> anybody got any
> > other suggestions?
> >
> > Thanks
> >
> > Gary
> >
> >
> > > -----Original Message-----
> > > From: JJ [mailto:jj5412@...]
> > > Sent: Friday, November 15, 2002 7:41 AM
> > > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > > Subject: RE: [CAD_CAM_EDM_DRO] L297/L298 board concern
> > >
> > >
> > > I think the suggestion that the Vref is to high is
> probably correct. I
> > > checked my L298s yesterday after a 4 hour run, and they were
> > > cool, close
> > > to ambient. I have multiwatt-15 heatsinks clipped on with thermal
> > > grease, and they're in an enclosure with a 100cfm fan
> blowing directly
> > > on them.
> > >
> > > Regards,
> > > JJ
> > >
> > > Be Kind, Be Careful, Be Yourself
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: B Snowden [mailto:bsnowde@...]
> > > > Sent: Friday, November 15, 2002 12:46 AM
> > > > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > > > Subject: Re: [CAD_CAM_EDM_DRO] L297/L298 board concern
> > > >
> > > >
> > > > Gary,
> > > >
> > > > I let the smoke out of one of my L298 also awhile back. Mine
> > > > had a heat sink on it. What I have now done, cut angle
> > > > aluminum to 6.75 in long. I have three L298's in a row. I
> > > > connected the aluminum
> > > > to the heat sinks of all three L298's. So what I end up with
> > > > is a heat sink attached to the heat sink of the three L298's.
> > > > When I get the board installed into a case, I plan to use
> > > > a fan to draw
> > > > air over the L298's. By adding the extra heat sink, I
> > > > dropped the temp from about 230+ F to around 160 - 205 F. I
> > > > do not know what the temp was when one of them smoked. The
> > > > fan should cool it even
> > > > more. I think you can get by without the extra heat sink,
> > > > but it would need to be installed in a case where a fan would
> > > > draw air over the L298's in a proper way. The extra heat
> > > > sink allows me to run
> > > > outside a case, and when I do install it, it should allow me
> > > > more margin, provided I have proper air flow.
> > > >
> > > > Bruce
> > > >
> > > >
> > > >
> > > > stirlinguy wrote:
> > > >
> > > > > Guys,
> > > > >
> > > > > I have a L297/L298 board that seems to be getting
> REAL hot. It's
> > > > > basically just the circuit from the L297 datasheet. A
> > > > friend of mine
> > > > > had the board made up with another order. I built it
> a few months
> > > > > ago, got a motor spinning (I think I was only using about
> > > 12v supply
> > > > > then), then put in on the shelf. I was playing with it today.
> > > > >
> > > > > When I run it, the L298 gets really hot. In fact, I
> didn't have a
> > > > > heatsink on it and the smoke got let out. After
> > > replacing the L298
> > > > > (and adding a heatsink), it seems to work OK, but
> still gets very
> > > > > hot. I don't want to run it too much for fear more smoke
> > > > may ruin my
> > > > > day.
> > > > >
> > > > > I am using a 24V power supply, the motor is a size 23
> > > that is rated
> > > > > for 3A, but should work fine with 2. It is stone cold
> > > when running
> > > > > at low speed from the driver. The L298 on the other hand
> > > could cook
> > > > > dinner.
> > > > >
> > > > > Anybody else have this problem? I'm not sure if
> there's something
> > > > > else screwy with the board, but the amount of heat I'm
> > > getting makes
> > > > > me wonder.
> > > > >
> > > > > Thanks in advance
> > > > >
> > > > > Gary
> > > > >
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> > OFF Topic POSTS: General Machining
> > If you wish to post on unlimited OT subjects goto:
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> to reach it if
> you have trouble.
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> >
> > http://groups.yahoo.com/group/jobshophomeshop I consider
> this to be a
> sister site to the CCED group, as many of the same members
> are there, for OT
> subjects, that are not allowed on the CCED list.
> >
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com
> to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider
> this to be a sister site to the CCED group, as many of the
> same members are there, for OT subjects, that are not allowed
> on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
> POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
> EXCEPTIONS........
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> List Mom
> List Owner
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