Re: L297/L298

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Phil Mattison"
<mattison20@...> wrote:

>
> I've been experimenting with various designs for bipolar
> stepper motor drivers and I'm curious if anyone has had a
> similar experience. Is it just my perception or is the
> L297/L298 combo a piece of junk? It seems no matter
> how I configure it the thing just runs way hot if it
> carries anything near its rated current.

Phil:

I'll give a somewhat contrarian point of view here.

The L298 is a bi-polar device and consequently
generates more heat in operation than its FET
counterparts (e.g. A3977.) With a good heat sink,
a fan and operated within specifications, L298's
operate just fine.

From a price point of view, they are still quite
competitive with their FET IC counterparts. For
example, the L298 can be purchased from Jameco
for less than $3 quantity 1. A heat sink for
the multiwatt15 package can be obtained from
Mouser for about $1 (Mouser #: 532-655010B3400G ~$1).
Of course, you also need some free wheel diodes like
the 1N5822, but those are inexpensive as well.

From a convenience point of view the FET IC's win
hands down. If you are only building one, the FET's
are the way to go. If you are thinking about building
hundreds, it is not as easy to dismiss the L298.

The L297 is at best a half step chip. These days
a micro-step solution tends to be preferred. It
is fairly easy to dump the L297 and replace it with
a microcontroller. My most recent table top drive
electronics are posted on-line at the following URL:

<http://gramlich.net/projects/cnc/axis4/index.html>

It works just fine. I make chips with my Sherline
CNC conversion using the driver above. I'm still
tweaking my total software toolset, but the basic
microstepper stuff using the L298's works quite well.
No, I can't step at 500kHz, but realistically I doubt
that most table top machines need to run quite that
fast. My driver won't win any IPM drag race derby's
but it will make chips just fine.

This is probably not be the consensus view on L298's.

-Wayne