RE: [CAD_CAM_EDM_DRO] Re: Higher power from L298 etc.

I was looking at the L6208 datasheet the other day, it's basically a 297 and
298 combined. When I tried to source it locally the suppliers had no idea
what I was talking about, eventually one said that the minimum amount that
they would bring in (to South Africa) is 800 pieces at $8 each... I THINK
NOT!!!

-----Original Message-----
From: JJ [mailto:jj5412@...]
Sent: Friday, November 08, 2002 2:57 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: Higher power from L298 etc.


As someone pointed out to me (forgot who, sorry), the L6203 has a higher
current rating than the L298. You also use 2 per axis. Total current per
device is 4A. They also don't require schottky diodes on the outputs.
Cost would be about US$15 per axis for the L6203s.

http://us.st.com/stonline/books/pdf/docs/1373.pdf

Regards,
JJ

Be Kind, Be Careful, Be Yourself

> -----Original Message-----
> From: Van Der Sandt Coert [mailto:vandersandtc@...]
> Sent: Thursday, November 07, 2002 7:20 AM
> To: 'CAD_CAM_EDM_DRO@yahoogroups.com'
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Higher power from L298 etc.
>
>
> No problem, I will check the boards and try to do a circuit
> layout. Better
> yet, I will take some pics and post them tomorrow.
>
> -----Original Message-----
> From: Tony Jeffree [mailto:tony@...]
> Sent: Thursday, November 07, 2002 12:55 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: Higher power from L298 etc.
>
>
> Apologies - disregard that comment - just spotted that you said 4
> L298's - the SGS Thompson config was 2 L298's. So they may well be
> right about 4A/phase. Apologies for the confusion. Presumably they
> are using 4 drivers in paralell for each phase. Interesting!
>
> Regards,
> Tony.
>
>
> --- In CAD_CAM_EDM_DRO@y..., Van Der Sandt Coert <vandersandtc@a...>
> wrote:
> > Oh OK - I suppose that the cards are over spec'd then. Good to know
> for
> > future ref.
> >
> > Thanks
> > Coert
> >
> > -----Original Message-----
> > From: Tony Jeffree [mailto:tony@j...]
> > Sent: Thursday, November 07, 2002 12:18 PM
> > To: CAD_CAM_EDM_DRO@y...
> > Subject: [CAD_CAM_EDM_DRO] Re: Higher power from L298 etc.
> >
> >
> > Yes, the SGS Thompson datasheet shows such a configuration;
> however,
> > they indicate a max of 3A (not 4A) DC and 3.5A repetitive (80:20
> duty
> > cycle with n on time of 10ms) for that configuration. So it sounds
> to
> > me like the boards you have are a touch over spec'd according to
> the
> > words in the SGS Thompson datasheet.
> >
> > Operating the drivers independently, the datasheet indicates
> 2A/phase
> > DC and 2.5A/phase repetitive. So by using an extra 297 to allow all
> 4
> > drivers to be current limited independently, it seems to me that
> you
> > could end up with 4A/phase DC and 5A/phase repetetive.
> >
> > Anyone know of/tried such a configuration?
> >
> > Regards,
> > Tony
> >
> > --- In CAD_CAM_EDM_DRO@y..., Van Der Sandt Coert
> <vandersandtc@a...>
> > wrote:
> > > Hi Tony
> > > I have four controllers (Avistep) that I bought surplus. Each
> > controller has
> > > four 298's and only one 297. Claimed current per phase is 4A. I
> > could never
> > > test this as none of my setups is that power hungry. My point is
> > that it is
> > > possible to get 4A / phase with 4 298 and one 297. Unfortunately
> I
> > do not
> > > have the circuit diagrams for the controllers only the physical
> > controllers.
> > >
> > > BTW : Has anyone ever heard of Avistep controllers? Net searches
> > don't seem
> > > to be able to find any references to these controllers.
> > >
> > > Cheers
> > > Coert
> > >
> > > -----Original Message-----
> > > From: Tony Jeffree [mailto:tony@j...]
> > >
> > >
> > > I was musing about the problem of getting better than 2A/phase
> out
> > of
> > > L298s (or better than 2.5A/phase out of Allegro 3977s). The
> > datasheet
> > > for the L298 suggests that it is possible to use 2 L298s, and
> > deliver
> > > 3A/phase, by paralelling the two driver stages in one 298 to
> drive
> > > one motor coil, and paralelling the other driver stages to drive
> > the
> > > second coil. Presumably, you can't get the full 4A/phase when
> doing
> > > this because of imperfect matching of the driver characteristics,
> > > which would cause one driver to take more of the current, and the
> > > current sense operates on the sum of the currents through each
> > > driver, leading to the danger of thermal runaway & release of the
> > > magic black smoke.
> > >
> > > It occurred to me that there is an alternative approach that
> could
> > > work with 8-wire motors; instead of wiring the L298 outputs in
> > > paralell, you use one half of a 298 to drive the A coil, and the
> > > other to drive the B coil; similarly, use one half of the second
> > 298
> > > to drive the A' coil, and the other half to drive the B' coil.
> > > Unfortunately, you would have to double up on L297's as well, in
> > > order to control all four coils independently; the step-and-
> > direction
> > > signals into these would simply be wired in paralell.
> > >
> > > All four drivers should then be able to operate up to their full
> > > 2A/phase, as they would be generating their own independent
> current
> > > sense signals back to their respective 297s. In effect, you would
> > > then have the same result as driving the 8-wire motor in bipolar
> > > paralell configuration, and would set the current limit on the
> > > drivers to 1/2 the value you would normally use for bipolar
> > paralell.
> > >
> > > Presumably this same approach could also be used with other
> driver
> > > chipsets such as the Allegro 3977, etc.
> > >
> > > So this would seem allow driving up to 4A/phase into 8-wire
> motors
> > > using two sets of 297/298, or 5A/phase using two 3977s.
> > >
> > > Can anyone see a problem with this approach (other than the cost
> of
> > > an extra chipset & ancilliary components per motor, and the
> > > limitation of using 8-wire motors)?
> > >
> > > Regards,
> > > Tony
> > >
> > >
> > >
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