Searching \ for '[PIC] High Power Stepper Motor Driver' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/ios.htm?key=stepper
Search entire site for: 'High Power Stepper Motor Driver'.

Exact match. Not showing close matches.
PICList Thread
'[PIC] High Power Stepper Motor Driver '
2004\10\15@221021 by Lee McLaren

flavicon
face
Hi All,

I am looking for a way to drive a high power stepper motor, my current
understanding (open to correction!) is that to achieve a high step rate with
good torque you need to drive say a 8A 3V stepper with 80v which of course
current limits to the appropiate value once the emf builds up. From my
research some of the commercial units use even higher voltages up to 180v to
maintain torque at high step rates.

There seems to be a lot of info on the web but very little when current and
voltage requirement get up a bit.

I have looked at the linistepper and quite a few others and have found a PIC
based stepper driver that that does the logic conversion  but I need to find
a suitable output stage, I am guessing that I will probably need some sort
of switch mode current limiter as a linear current limiter would have a very
hign dissipation (800w!). FETs seem to be common in this area but again I am
open to suggestions.

I am also looking for a source of large stepper motors in the area of 5NM or
700 Oz/inches holding torque.

Any suggestions?


regards

Lee McLaren

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\15@224058 by Dave VanHorn

flavicon
face

>
>I have looked at the linistepper and quite a few others and have found a PIC
>based stepper driver that that does the logic conversion  but I need to find
>a suitable output stage, I am guessing that I will probably need some sort
>of switch mode current limiter as a linear current limiter would have a very
>hign dissipation (800w!). FETs seem to be common in this area but again I am
>open to suggestions.

Look at the data sheets on the PBL3717 or similar chopped current stepper
drivers.
This should help.

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\15@233522 by Lee McLaren

flavicon
face
Thanks Dave, the PBL3717 looks a little light on for my needs, I need at
least 8Amps and would like the voltage up around 100v at least.

regards

Lee McLaren

{Original Message removed}

2004\10\16@002626 by Dave VanHorn

flavicon
face
At 10:28 PM 10/15/2004, Lee McLaren wrote:

>Thanks Dave, the PBL3717 looks a little light on for my needs, I need at
>least 8Amps and would like the voltage up around 100v at least.

Yes, I just thought you'd find the general technique informative.


_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\16@152504 by Peter L. Peres

picon face

On Sat, 16 Oct 2004, Lee McLaren wrote:

> Hi All,
>
> I am looking for a way to drive a high power stepper motor, my current
> understanding (open to correction!) is that to achieve a high step rate with
> good torque you need to drive say a 8A 3V stepper with 80v which of course
> current limits to the appropiate value once the emf builds up. From my
> research some of the commercial units use even higher voltages up to 180v to
> maintain torque at high step rates.

You *must* obatin data sheet data about the motor insulation being able to
withstand 160V at least (preferraby 320V) before you can use it with
voltage forcing.

Look into chopper drives.

Peter
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\16@152542 by Peter L. Peres

picon face

On Sat, 16 Oct 2004, Lee McLaren wrote:

> Thanks Dave, the PBL3717 looks a little light on for my needs, I need at
> least 8Amps and would like the voltage up around 100v at least.

So you'd like to design a 1HP chopped mode stepper driver from scratch,
with no previous experience, using free advice from the piclist, and use a
25 watt stepper for that ?

Peter
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\16@183027 by Lee McLaren

flavicon
face
Well I wouldn't say no previous experience, I am a electronics tech but I am
new to the area of stepper motors, the motor spec sheets show step rates up
to 180v so I am not concerned about the motor insulation breaking down.

I don't see how you get 1HP, the stepper is rated at say 8A and 0.45Ohm
coils which are paralleled for a bipolar drive, while you supply 100v it is
current limited. So while the initial voltage per step is high it will
quickly drop down to what it is current limited to, so I would suggest that
the power is closer to 100w not 760 but the output need to be able to handle
the voltage.

I have been doing a lot of research on the National and IRF sites so "using
free advice from the piclist" is not the only resource.

As there is considerable interest on the list with CNC I would of thought
that others may be in the same position this may be of help.
I started with a hobbycnc stepper driver and motors but quickly realized
that the drive needs for my mill exceeded the 80oz stepper that I have.

I am using a PIC to create all the logic level stuff and are collecting info
for the output stage and if someone had a pointer for a ref design then that
would help.

And yes I do expect to have to use a chopped mode of some sort as the power
dissipation in the driver will be huge otherwise.

Does this answer your question Peter?

regards


Lee McLaren


{Original Message removed}

2004\10\16@193414 by steve

flavicon
face
Lee,

Peter has a point. There's a big difference between a drive for an 8A
motor and a 1A unipolar or linstep drive.
During your research, you will have probably noticed that there are very
few independent drive manufacturers for motors that big. Most CNC
retrofits are around half that size. The standard solution would be a
microstepping chopper drive. Then you run into mid-band resonance
issues and the drive manufacturers tend to keep their solutions to
themselves.
Nothing is impossible, but you are unlikely to find many other people in
a similar situation.

My first question would be, of you need that much power, why a stepper
and not a servo ?
My second would be, how much are you paying for 8A motors ?

Steve.


On 17 Oct 2004 at 9:24, Lee McLaren wrote:

{Quote hidden}

> {Original Message removed}

2004\10\16@202427 by Lee McLaren

flavicon
face
Hi Steve,

The mill I am trying to drive is around 370Kg and my testing so far has
been:

80 Oz inch stepper with 5:1 reduction        Skips with small amount of presure on
table and very very slow table movements
                                                       Step rates around 15 / sec.
110 Oz inch        direct couple                        Lot better than 80 Oz, works ok with no load on
table and low step rate say around 20 / sec
                                                       Almost usable but I am worried when the load increases.

Both of these are using a unipolar drive of 1.5 and 3A @ 40v chopper.

I can buy a 5.1 Nm (700 Oz) (Sanyo Denki p# 103-845-6741) stepper for around
$360 AUD which requires 10A per phase and to get the most benifit I will
need to use a bipolar drive.
The spec sheet show curves for diff voltages between 75 and 180 volts, I
expect the torque / step rate will drop a lot below this voltage.

I love the idea of using servos but my research shows them costing twice the
price of steppers.
I am open to going either way and are looking for advise. I could almost get
away with the 110 Oz stepper I expect if the drive is right but I will be
right on the edge.


thanks


Lee McLaren


{Original Message removed}

2004\10\16@211158 by hilip Stortz

picon face
i was recently interested in steppers myself, and good chopper drivers.
i found a lot of application notes with a web search and learned a great
deal of the theory, which is applicable with any particular driver
solution.  you definitely have to check what the motor insulation will
tolerate.  

you definitely want to use fets.  there are any number of chips useful
for making the current chopping part or most of the driver minus the
fets.  a lot of the design depends on whether or not you want to
microstep and how finely you want to microstep (it doesn't make a lot of
sense to microstep very finely usually as most motors are not very
linear or sinusoidal between steps though some are designed to be it is
unusual).  you definitely want to make the system very, very robust and
abuse tolerant, you are dealing with high power levels and large
inductors switched at fairly high frequencies, it is not a friendly
environment for man or discrete component.  also, as only a few sources
i found mentioned, a small cap across the windings at the motor is
probably a very good idea.  i'd also strongly consider coax or twinax
for the wiring, or some well shielded cable.

note also that there are several ways of handling the "idle" current of
the motor windings and these affect the dampening of the system and
depending on how fast things are moving different schemes make more
sense, for systems that can eventually reach high step rates it's not
uncommon to see different methods used at different speeds.  all in all
i came away realizing that steppers are an excellent example of a non
ideal system and that dsp probably has value in a high performance system.

the power supply is also a large issue.  my friends small mill system
uses a "linear" 60 hz transformer power supply, which is huge and
dissipates considerable power.  i will be trying to replace this with a
switching power supply simply for efficiency sake though even the power
supply for steppers is not a simple problem.

remember you are going to need at least 360W of power supply capacity
per winding, i would highly recommend a switching power supply if at all
possible.  note also that at rest each winding will only need 24W and
the chopper will be working hard drawing power in narrow spikes from the
power supply.

you are designing a very high performance system, expect some parts of
the implementation to be complex and think creatively.  also look at
chips from many manufacturers.  i've considered using switching power
supply chips as part of the driver circuitry, i.e. for the current
regulation, this may be a good approach for your system.

i believe TI or national had extensive information on driving steppers.
a web search and lots of downloading of acrobat files is in order, it's
best to save all the application notes you find, even those which don't
immediately seem useful.  the data sheets and application notes for
lower current single chip solutions are very informative in many cases.

"Peter L. Peres" wrote:
>
> On Sat, 16 Oct 2004, Lee McLaren wrote:
>
> > Hi All,
> >
> > I am looking for a way to drive a high power stepper motor, my current
> > understanding (open to correction!) is that to achieve a high step rate with
> > good torque you need to drive say a 8A 3V stepper with 80v which of course
---------

--
"We cannot simply suspend or restrict civil liberties until the War of
Terror is over, because the
War on Terror is unlikely ever to be truly over," Judge Gerald Tjoflat
wrote for the three-member
court. "September 11, 2001, already a day of immeasurable tragedy,
cannot be the day liberty
perished in this country." <http://www.cnn.com/2004/LAW/10/16/protesters.terrorism.ap/index.html>

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\16@211733 by hilip Stortz

picon face
and who makes large servo and stepper motors?  and by "servo motors" i
assume we mean well behaved dc motors with rotary encoders?

spam_OUTsteveTakeThisOuTspamtla.co.nz wrote:
---------
> My first question would be, of you need that much power, why a stepper
> and not a servo ?
> My second would be, how much are you paying for 8A motors ?
>
> Steve.
-------

--
"We cannot simply suspend or restrict civil liberties until the War of
Terror is over, because the
War on Terror is unlikely ever to be truly over," Judge Gerald Tjoflat
wrote for the three-member
court. "September 11, 2001, already a day of immeasurable tragedy,
cannot be the day liberty
perished in this country." <www.cnn.com/2004/LAW/10/16/protesters.terrorism.ap/index.html>
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\17@002428 by Lee McLaren

flavicon
face
Thanks for the advise Philip,
I expect I don't really need microstep and FETS where looking to be the best
option from my research as well, for a power supply I was just going to get
a mains 240 - 120v transformer and feed it through a rectifier if my output
stage can handle the voltage. I expect I don't want anything to go wrong
though!

Large (by my standard) motors are available from Sanyo Denki and a spec
sheet can be got from http://www.automotsys.com.au the one I am considering is
5.1Nm holding torque and around 4Nm at 15 rps if driven from 180v.

I like the idea or using servos but don't know of a cheap source, I was
considering modifying a geared 24v DC 250W motor and adding an encoder but I
am worried that the backlash in the gearing would cause problems
http://www.oatleyelectronics.com/images/sc250g.jpg

regards

Lee McLaren



_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\17@020420 by hilip Stortz

picon face
on further thought...  microstepping can help with resonance problems,
so it may be worthwhile to use it at the speeds where that is a problem
(not using it at higher speeds makes sense since you should have a large
ratio between your chopping frequency and your step frequency).  

also, a trick i learned that worked very well for damping oscillation is
to coat things with heat shrink tubing.  in this case they were tripod
legs, about 4" in diameter made from hollow heavy wall aluminum tubing
on an instrument that was very vibration sensitive (enough that a "super
spring", i.e. an active electro mechanical spring) sat below it on
another tripod.  putting heatshrink over the hollow legs made them
completely dead, though it was necessary to first spray them with
silicone conformal coating to keep the heatshrink in place over the long
run (silicone is one of the few adhesives i've found that works well
with pvc, and it was pvc heatshrink).  of course for this application
you want the soft, almost gooey heatshrink (and hopefully not in that
large a size or it will cost as much as motors!).  

other things that occur to me but i have no data on that might help
resonance would be applying short pulses to the opposite set of coils
(though that would be tricky) to round the edges as it were (i.e.
reducing the sharpness of the torque change).  anything to make the
mechanical system more dead would definitely help, the heatshrink tubing
could be put on the shafting and there are deadening materials that can
be applied other places as well, if you can find one thermally
conductive it could also be put on the motor though i don't know of any
such material (other than greases, which could be ok if you built a
secondary enclosure around the motor and filled it with a thermally
conductive grease, most of which are very dead).  in any case dampening
material on the other flat surfaces of the bracketing etc. should help.
there are probably also solutions involving a viscous oil and vane type
of affair thou those would also tend to limit maximum speed (which seems
to be very important in your case).  in any case, the proper lubricant
on the lead screws might help resonance problems.  i suspect a web
search might turn up some useful ideas and a lot of not so useful ideas
(i often wind up doing considerable sifting through search results, but
i'm often looking for odd information).  

protecting the lead screw from oscillating is definitely important, i
think i'd use microstepping and consider filling it's area with grease
even it it slightly increased the dynamic load.  in any case it's
definitely something you want to keep an eye on in testing.  i suppose
magnetic dampening could be used, with strong rare earth magnets along
the length of the lead screw or in a few well chosen places, interrupted
magnets would effectively shorten the length of the free part of the
lead screw and raise the critical frequency.  all in all though probably
best to avoid cogging near critical speed by any means necessary.

your application almost sounds as if it could benefit from a multi-speed
transmission, though that would complicate positioning unless used as
part of a servo system.

i've seen home built cnc mill modifications that used a timing belt and
pulleys, which would make backlash less of a problem for a servo system.
i believe in any case that with a servo design you want the encoder
right on the lead screw, though backlash could still cause oscillation problems.

i do like your' idea of using a linear supply to start with at least,
big, ugly, and heavy but the toughest solution possible.  just remember
to consider the ripple current of your filter capacitors and provide
them with plenty of forced air cooling!  the first thing i did when i
saw my friends setup was to get him another capacitor that would be able
to handle the ripple current, you often have to use one much larger than
what you need for filtering although this makes it harder on the
transformer and rectifier since it decreases ripple voltage and
increases the ripple current still more.  (physically smaller capacitors
are often a bad idea for power supplies because of the heat from ripple
current that must be dissipated, and i have seen heatsinks on power
supply caps before!).

Lee McLaren wrote:
>
> Thanks for the advise Philip,
> I expect I don't really need microstep and FETS where looking to be the best
> option from my research as well, for a power supply I was just going to get
> a mains 240 - 120v transformer and feed it through a rectifier if my output
> stage can handle the voltage. I expect I don't want anything to go wrong
> though!
----------

--
"We cannot simply suspend or restrict civil liberties until the War of
Terror is over, because the
War on Terror is unlikely ever to be truly over," Judge Gerald Tjoflat
wrote for the three-member
court. "September 11, 2001, already a day of immeasurable tragedy,
cannot be the day liberty
perished in this country." <www.cnn.com/2004/LAW/10/16/protesters.terrorism.ap/index.html>
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\17@053207 by William Chops Westfield

face picon face

On Oct 16, 2004, at 3:24 PM, Lee McLaren wrote:

> I don't see how you get 1HP, the stepper is rated at say 8A and 0.45Ohm
> coils which are paralleled for a bipolar drive, while you supply 100v
> it is
> current limited.

Hmm.  i've never designed or used a high power stepper, nor even
researched them very deeply, but the current discussion isn't matching
what I THOUGHT I understood very well...

Isn't your current limited by the .45Ohm coil resistance only?
At 100V, that looks like 200+ Amps to me.  Since the coils are only
spec'ed for 8 amps, limiting the current has to happen outside the
stepper itself, doesn't it?

The "kick"  is that when you attempt to move the rotor, the current
through the winding is no longer limitted by the steady state
resistance,
but by the inductance; for a step applied voltage, you a nice
exponential
multiplied by V.  To get the 8A you want through the coil for max
torque,
thoughout the pulse, you have to apply a much higher voltage and either
make it a complex waveform v(t) or separately current-limit via chopping
or big R or something.  Since V isn't constant, you can get power via
I*I*R, and since I is supposed to be 8A always, that's still ~30W for
the motor (and from the power supply, unless you're dissipating it
elsewhere.)  What you really want from your power supply is a constant
current driven into inductive loads, with complications when (if?) the
inductance isn't constant either as the windings come inline with
magnets,
and/or electrical energy is converted to motion...

BillW

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\17@060916 by hilip Stortz

picon face
exactly!  hence the desire for a high drive voltage, with current
limited by "chopping", i.e. turning the power source on and off and
providing a path for the back emf induced current until it drops bellow
8 amps, and then turning the power back on until it just exceeds 8 amps,
typically at 1khz to 150khz or better.  this is the only way to get high
step rates out of a stepper motor.  this system is more drastic than
most, i.e. smaller systems may use 5V motors with a 24V supply, but it's
the same idea.  the current limit is incorporated directly into the
drive electronics for each coil, and usually has to supply either
polarity so a full bridge is usually used.  for smaller motors, up to
2.5A at least there are single chip solutions that drive both coils and
handle the current limit, and even provide some microstepping (smaller
steps produced by providing current to roughly both windings in sin and
cos magnitude proportions at some number of intermediary electrical
degrees of rotation, easily done by varying the reference of the current
limit circuitry).  it isn't pretty, but it works very nicely.  

there are simpler methods that don't work as well, such as using a
higher voltage and a series resistor, or applying a higher voltage for a
specific time period and then switching to the "rated" voltage for
normal current.  i've seen old 8" floppy drives that used the series
resistor approach for instance on the head motor.

William Chops Westfield wrote:
-------
> The "kick"  is that when you attempt to move the rotor, the current
> through the winding is no longer limitted by the steady state
> resistance,
> but by the inductance; for a step applied voltage, you a nice
> exponential
> multiplied by V.  To get the 8A you want through the coil for max
> torque,
> thoughout the pulse, you have to apply a much higher voltage and either
> make it a complex waveform v(t) or separately current-limit via chopping

-------

--
"We cannot simply suspend or restrict civil liberties until the War of
Terror is over, because the
War on Terror is unlikely ever to be truly over," Judge Gerald Tjoflat
wrote for the three-member
court. "September 11, 2001, already a day of immeasurable tragedy,
cannot be the day liberty
perished in this country." <www.cnn.com/2004/LAW/10/16/protesters.terrorism.ap/index.html>
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\17@202803 by Peter L. Peres

picon face

On Sat, 16 Oct 2004, Peter L. Peres wrote:

> On Sat, 16 Oct 2004, Lee McLaren wrote:
>
>> Thanks Dave, the PBL3717 looks a little light on for my needs, I need at
>> least 8Amps and would like the voltage up around 100v at least.
>
> So you'd like to design a 1HP chopped mode stepper driver from scratch, with
> no previous experience, using free advice from the piclist, and use a 25 watt
> stepper for that ?

8A * 100V > 1HP. You would like these to manifest themselves one at a time
(not together) but while developing circuits accidents will happen. A
device that switches 8A and withstands 300V will often be rated at more
than 150 Watt allowed dissipation. Maybe 1HP is exaggerating a little but
be prepared for fireworks while experimenting.

Peter
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

2004\10\19@232917 by PicDude

flavicon
face
Lee,

Another slightly delayed response, but I might be able to offer some
assistance...

First, 8A is *significant*.  What motor is this for?  If you are looking for
~700 oz-in motors, you won't need 8A.  Check out
http://www.seanet.com/~dmauch/ .  He has steppers in this range, which many
people on the lathe/mill/CNC lists are happy with.  As an example, he has a
680 oz-in motor, requiring 2A, for $95 each.

For the drivers, check out Microchip's AN906 and also the datasheet for
National's LM18245 stepper driver chip.  These explain a lot of how to design
a stepper driver and about microstepping, etc.

(Currently, I'm building a couple 3A bipolar stepper drivers using the LM18245
chip for my CNC lathe conversion.)

You should also get on some of the CNC discussion lists on yahoo groups such
as DIY_CNC, CAD_CAM_EDM_DRO, and others.

Cheers,
-Neil.



On Friday 15 October 2004 09:03 pm, Lee McLaren scribbled:
{Quote hidden}

____________________________________________

2004\10\25@054701 by hilip Stortz

picon face
you might want to check at jameco.com, they have some very large
steppers and servo motors, cheap.  some are in the range you are
planning on using and they have a fairly large selection.  they must be
surplus, but they are new.  they even have the smaller steppers i want
with dual shafts for about $2.50 each!  they look even better than ebay.

Lee McLaren wrote:
--------
> Large (by my standard) motors are available from Sanyo Denki and a spec
> sheet can be got from http://www.automotsys.com.au the one I am considering is
> 5.1Nm holding torque and around 4Nm at 15 rps if driven from 180v.
-------

--
Some people embrace change and the unknown.  Some people are afraid of
the unknown and change.  George Bush is not only
afraid of change, he is afraid of the present.  George Bush's world is
based on fear and distrust, he is incapable of
trusting anyone or of receiving love and joy.  The world only makes
sense to Bush when there is a threat, if Al Queda
did not exist Bush would have to invent them for the world to make sense
to him.  Do we want a leader who's life is
based on fear and distrust or one who will embrace change and the
unknown and lead us with hope into a more joyful
future?
<http://www.philly.com/mld/dailynews/news/columnists/9963983.htm?1c> <http://www.leinsdorf.com/2004/Soaries.htm>
<www.informationclearinghouse.info/article6505.htm>
____________________________________________

2004\10\25@111431 by Bob J

picon face
Lee,
Given your stepper motor current requirements and the fact that you
are building a CNC system, save yourself some hassle and buy a set of
gecko drives (http://www.geckodrive.com).  They are pretty much the de-facto
standard drives for low cost CNC conversions and are very popular,
very reliable, and have good support.  The G201 is priced $114 each,
you'll need one for each axis, and of course will have to build your
own power supply for the system.  There is a lot to keeping a
larger-sized stepper motor happy and running, I would not recommend
building a step-direction driver yourself if its anything larger than
lets say a robotics application.

Regards,
Bob
____________________________________________

More... (looser matching)
- Last day of these posts
- In 2004 , 2005 only
- Today
- New search...