Re: Question For Dan Mauch

I have some of those drives. The ones that I got came from General
Controls. They got them from SGS.
They are actually pretty good drives- they ran very well, seemed immune to
electrical noise, never blew up :) I don't think that you could use them
to piggyback on to bigger mosfets and still have current limiting/control.
The L297 has a pin on it that reads the voltage going across a sensing
resistor that indirectly tells it how much current the H-bridges is
outputting. You would need to be able to gain access to this resistor and
even then, you don't have the the phase outputs from the L297 (a, A, b, B).
So, you would be better off starting from scratch on that one. One thing
that the SGS book says is possible is to run several L298s or L6203s (3 amp
pentawatt chip) in parallel. But, sadly, in practice a lot of people have
found that this isn't reliable. Check out the Stepper motor discussion
forum at www.eio.com. There is a lot of info on the SGS stuff.
The dallas robotics club has a web page that shows a rough sketch of a
scaled up L298. I think that Roger Arrick drew this on a piece of paper-
but I don't know if it's been tested. It is described as being capable of
10 amps or more using big-ass mosfets. You would need to build two of
these H-bridges to replace every L298.
My favorite DIY stepper drive is the Ericsson design that Dan Mauch has
now. It uses 2 ICs and 8 mosfets to put out over 5 amps. Apparently, with
good design, and good shielding, good airflow, it should be able to put out
10 amps- I ran 9 amps for a little while, before roasting some mosfets.
Ask Dan about the 5amp boards/kits.

Dan Falck
Nashville,TN.

At 08:01 PM 5/29/99 -0500, you wrote:

>From: William Scalione <scalione@...>
>
>Dan, or anyone else who might know;
>
>Have you ever tried to use an SGS Thompson GS-D200? It is basically a
>L297/L298
>with most of the glue components in one module. Add a couple resisters,
>a current limiting pot and some wire and your done. What I was wondering
>about was
>since the output is only 2 amps could those outputs be run into some
>high power
>transisters to acheive approx 10 amps. If so how would the current
>limiting be
>accomplished? Design so the gain of the output transisters is approx. 5
>then
>adjust the current limiting pot on the GS-D200 (or L297/L298 combo) to
>equal 2
>amps at the output of the H-Bridge (2A * 5 = 10A)?
>
>Thanks
>
>Bill
>
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