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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 Mattison

Phil,
There are some threads on these chips on
<>. My memory is that
they were not very complimentry. There seem to be better single chip
solutions available such as the ones used by
<>. As for me, I'll stick with Gecko's. I'm
way more interested in chips and machines than electronics :->

Roger

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 Mattison

Phil Mattison 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.

This is at least 15 year-old technology, and way past obsolete. it is using bipolar
transistors, for instance, not FETs. I used it in a project I built in 1991 or so, and it
was a mature product then!

Jon

Phil Mattison 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.

Needs a good heatsink ;)
No problem in Divisionmaster, and the three channel NCStep board runs nicely, but I'm sticking with the LMD18245 for the single channel controller. EAS have done a good job with the PCB for that.

--
Lester Caine - G8HFL
-----------------------------
L.S.Caine Electronic Services -
Model Engineers Digital Workshop -
Treasurer - Firebird Foundation Inc. -

--- In CAD_CAM_EDM_DRO@..., "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:

<>

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

In a message dated 8/4/2006 3:26:02 P.M. Central Daylight Time,
johnd@... writes:

The L298 is a bi-polar device and consequently generates more heat in
operation than its FET counterparts<<
I think someone should clarify "bipolar" as used here for the non-techie
types:

There are basically TWO realms of semiconductors, those like diodes and NPN
and PNP transistors are called "bipolar;" and the other kind, "FET's"
(Field-Effect Transistors).

This should NOT be confused with "bipolar steppers and drivers!" "UNIpolar"
stepper-drivers have four transistors that alternately connect two
motor-wires to negative, the positive "always" supplied via center-taps in the two
windings in "UNIpolar" motors.

"BIpolar" motors have two windings with NO center-taps, and the two wires
per winding (four such wires in all) are "fed" positive and negative by the
driver, and this polarity is simply SWAPPED to negative and positive,
respectively, first in ONE winding for ONE step and then in the other winding for the
NEXT step, and so on.

A "Bipolar driver" can be made with EITHER "bipolar" or "FET" transistors!
Sorry if I've confused you all by my poor explanation! JRR

Hi Wayne,
You make some good points. I was looking at the L298 mainly because it's
cheap and abundant. The LMD18245 looks really swell but at over 6X the cost
(since you need 2) it changes the economics quite a bit. I've seriously
considered going to discreet MOSFETs but the gate drive requirements for the
high-voltage MOSFETs looks like a real pain in the keester. Sure would be
nice if you could get discreet high-voltage MOSFETs with built-in gate
drivers to accept logic-level control signals. Haven't been able to find
anything like that. Anyone seen such an animal?

I've been working on a controller for serial communications as well using a
PIC16C745, and have been able to generate rapid moves up to 50 KHz with
trapezoidal acceleration profiles. Better than I expected. Certainly not
adequate for high-speed servo drives with 1024-step encoders, but plenty
adequate for many hobby applications, especially for steppers. Anyway,
unless you're using a really coarse pitch lead screw or big gear reduction,
a 1024-step shaft encoder seems like major overkill to me. Most hobbyists
seem to be looking for bargains, and overkill is counter-productive in that
quest.
--
Phil Mattison

Phil Mattison wrote:

Hi Wayne,
You make some good points. I was looking at the L298 mainly because it's
cheap and abundant. The LMD18245 looks really swell but at over 6X the cost
(since you need 2) it changes the economics quite a bit. I've seriously

It is worth bearing in mind here that the LMD18245 has the output diodes built in, and does not need a large current resistor. Saves on the additional component costs, and reduces board area.
Perhaps if we can get a few more people using it we can get volumes up and the price will come down. I need another 20 for the next batch of kits ;)

--
Lester Caine - G8HFL
-----------------------------
L.S.Caine Electronic Services -
Model Engineers Digital Workshop -
Treasurer - Firebird Foundation Inc. -

Nicely done Wayne.

John Dammeyer

I was going to build something like one of these

since it looks like a bulletproof version of the standard L297 + L298-based
circuits, as I have on breadboards hooked up to the steppers on my mill. I
think I will build pminmo's version, because it will work, and is just an
upgrade of what I already have, and then later I can swap them out for
something more sophisticated when I need to.

The reprap group is mucking about with a dozen different things. I'm fairly
certain we're going to end up with one PIC16Fxxxx per axis, I don't know
about the drive chips although we're toying with L298s this week. Some of
the PIC16F and PIC18F chips will do usb, which will be handy:


We're using the SNAP protocol to send orders from the master microcontroller
to each axis, but I think we're going to tweak it a bit. Or toss it.

I haven't built any of these things, or even built a microcontroller
programmer yet, but:
Here's a stepper driver with a PIC16F chip and a UDN2559


Some other varients, via searching for "stepper" in






I have a question regarding servos versus steppers:
Steppers seem fairly standardized. I can specify a bipolar 1.8 degrees/step
nema 23 mount stepper in a parts listing, and know that a reprap builder can
find one. How standardized are servo motors - is each model unique, or can I
specify a motor with certain characteristics and know that people will be
able to find them? If I'm doing a cnc conversion on a mill, I'm willing to
design my circuits, motor mounts, and shaft adapters around what I can
scrounge. For several thousand user-built machines, it's not clear to me
that I can specify servos.

We're thinking of building linear encoders along each axis, based on photo
etched dots on metal sheet, or something, so who knows what we'll end up
doing?

-Sebastien

HI Phil,

It's an old part! Check out the Semiconductor LMD18245 and the EAS website
I posted.

Alan KM6VV

Hi Jan,

Perhaps set up your quoting of messages a bit clearer. I did not write the
fragment below. The credit for that goes to Wayne Gramlich who has a pretty
nice implimentation. All I did was compliment him for posting the entire
thing on his web site.

John Dammeyer

================

In a message dated 8/4/2006 3:26:02 P.M. Central Daylight Time,
johnd@... writes:

The L298 is a bi-polar device and consequently generates
more heat in
operation than its FET counterparts<<

================

I think someone should clarify "bipolar" as used here for the
non-techie
types:

There are basically TWO realms of semiconductors, those like
diodes and NPN
and PNP transistors are called "bipolar;" and the other kind,
"FET's"
(Field-Effect Transistors).

This should NOT be confused with "bipolar steppers and
drivers!" "UNIpolar"
stepper-drivers have four transistors that alternately connect two
motor-wires to negative, the positive "always" supplied via
center-taps in the two
windings in "UNIpolar" motors.

"BIpolar" motors have two windings with NO center-taps, and
the two wires
per winding (four such wires in all) are "fed" positive and
negative by the
driver, and this polarity is simply SWAPPED to negative and
positive,
respectively, first in ONE winding for ONE step and then in
the other winding for the
NEXT step, and so on.

A "Bipolar driver" can be made with EITHER "bipolar" or "FET"
transistors!
Sorry if I've confused you all by my poor explanation! JRR




[Non-text portions of this message have been removed]



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--- In CAD_CAM_EDM_DRO@..., JanRwl@... wrote:

In a message dated 8/4/2006 3:26:02 P.M. Central Daylight Time,
johnd@... writes:

The L298 is a bi-polar device and consequently generates more

heat in

operation than its FET counterparts<<
I think someone should clarify "bipolar" as used here for the non-

techie

types:

There are basically TWO realms of semiconductors, those like

diodes and NPN

and PNP transistors are called "bipolar;" and the other

kind, "FET's"

(Field-Effect Transistors).

This should NOT be confused with "bipolar steppers and

drivers!" "UNIpolar"

stepper-drivers have four transistors that alternately connect

two

motor-wires to negative, the positive "always" supplied via

center-taps in the two

windings in "UNIpolar" motors.

"BIpolar" motors have two windings with NO center-taps, and the

two wires

per winding (four such wires in all) are "fed" positive and

negative by the

driver, and this polarity is simply SWAPPED to negative and

positive,

respectively, first in ONE winding for ONE step and then in the

other winding for the

NEXT step, and so on.

A "Bipolar driver" can be made with EITHER "bipolar" or "FET"

transistors!

Sorry if I've confused you all by my poor explanation!

JRR

All:

Yikes! Both John and Ballendo are correct. I was
using the "techie" terminology for silicon transistors.
The first transistors that were invented are called
PNP and NPN silcon transistors (actually they used
Germanium first; but I digress.) Silicon transistors
drop .2 volts when they are saturated and consequently
radiate .2V * (current) watts of heat. For the L298,
if you have 4 coils turned full on, that 4 (coils) *
(2 amps) * .2 volts = 16 watts. This is quite hot and
needs a heat sink.

FET (field effect transistors) are newer and have
a lower voltage drop when the are "on". Thus, they
radiate much less heat. I'm not as comfortable talking
about FET's, since most of my experience is with the
older silicon NPN/PNP transistor techonology. I'll
let other more experienced people on the list chime
in about FET transistors.

-Wayne

P.S. I'm out on vacation, and my internet access is
kind of spotty; hence, the delay in my responses.

A MOSFET does have a region between full-on and full-off where it acts like
a linear device, i.e. source-drain current is proportional to the gate
voltage. If operated in this region it will dissipate as much heat as a
bipolar (silicon junction) transistor. This is why fast switching is so
important with MOSFETS. Actually both types are made of silicon, they just
operate differently. Bipolar transistors are controlled by current and FETs
are controlled by voltage.
--
Phil Mattison

All:

Yikes! Both John and Ballendo are correct. I was
using the "techie" terminology for silicon transistors.
The first transistors that were invented are called
PNP and NPN silcon transistors (actually they used
Germanium first; but I digress.) Silicon transistors
drop .2 volts when they are saturated and consequently
radiate .2V * (current) watts of heat. For the L298,
if you have 4 coils turned full on, that 4 (coils) *
(2 amps) * .2 volts = 16 watts. This is quite hot and
needs a heat sink.

FET (field effect transistors) are newer and have
a lower voltage drop when the are "on". Thus, they
radiate much less heat. I'm not as comfortable talking
about FET's, since most of my experience is with the
older silicon NPN/PNP transistor techonology. I'll
let other more experienced people on the list chime
in about FET transistors.

-Wayne

P.S. I'm out on vacation, and my internet access is
kind of spotty; hence, the delay in my responses.





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subjects, that are not allowed on the CCED list.

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Just blew a set when trying to clear a problem on a customers DivisionMaster. Looks like a short between pins which only became a problem when you drive the motor in continuous mode.

The L297/L298 seem quite forgiving on the actual output, but make sure that the interconnecting wiring is clean before powering the circuit up!

It's annoying because I have not had any real problems with the pair up until now.

--
Lester Caine - G8HFL
-----------------------------
L.S.Caine Electronic Services -
Model Engineers Digital Workshop -
Treasurer - Firebird Foundation Inc. -

This is a really old thread, but I am just catching up on my email and
wanted to add my 2c, for the record:

The one advantage of L297/L298 solution is that you can chain several L298
chips in parallel. You can't do that with an LMD18245. Yes, the PCB routing
gets hairy pretty quickly, but it can be done, and it works. I am currently
using boards utilizing that very method - 3 L298 chips in parallel per axis
driving stepper motors with 5A per axis (

).

Of course, one could argue that if higher currents are needed, one should
just go with discreet FETs anyway, and I wholeheartedly agree, but that's a
different topic. The point is that, in a pinch, you could get some extra
power out of a L297/L298-based solution, and it is a remarkably simple
circuit.

Vlad

--
Vlad's shop

--- In CAD_CAM_EDM_DRO@..., "Vlad Krupin" <vlad.cnc@...>
wrote:

This is a really old thread, but I am just catching up on my email and
wanted to add my 2c, for the record:

The one advantage of L297/L298 solution is that you can chain

several L298

chips in parallel. You can't do that with an LMD18245. Yes, the PCB

routing

gets hairy pretty quickly, but it can be done, and it works. I am

currently

using boards utilizing that very method - 3 L298 chips in parallel

per axis

driving stepper motors with 5A per axis (

).

Of course, one could argue that if higher currents are needed, one

should

just go with discreet FETs anyway, and I wholeheartedly agree, but

that's a

different topic. The point is that, in a pinch, you could get some extra
power out of a L297/L298-based solution, and it is a remarkably simple
circuit.

Vlad

Hi Vlad,

I thought that using big power FET's was a super simple solution to
the higher power problem ?

Dave

On 9/2/06, turbulatordude <dave_mucha@...> wrote:
[snip]

Hi Vlad,

I thought that using big power FET's was a super simple solution to
the higher power problem ?

Not necessarily super-eimple, at least not for me, but yes, indeed, this is
the solution. You are absolutely correct. Just to quote myself from the
previous email:

Of course, one could argue that if higher currents are needed, one should
just go with discreet FETs anyway, and I wholeheartedly agree

:)

I was merely underlying the advantages of using L298 in some applications.

Vlad


Dave

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--
Vlad's shop