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'[EE]: Some stepper motor advice, please'
2002\02\23@120125 by michael brown

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I am working on a robot when I have a little spare time (who isn't ;-D)  My
first attempt involved using motors from old 5.25" floppy drives.  They are
cheap and easy to work with, but have virtually no power.  They are 4-phase
motors, making it easy to drive them.  I now need more power, and I found
some cheap(US$7.00) surplus Vexta NMEA-17 2-phase motors.  These motors are
rated at 6V .8A.

My old driver board uses TIP-120's driven thru a buffer IC with extra bypass
diodes added.  These had no trouble with the floppy motors even without heat
sinks.

Now for the questions:

1  Since these are 2-phase, do I absolutely have to flip polarity's on the
winding coils to get the motors to run?  These motors have 6 wires, so it
seems that they are center tapped.  Maybe I can just tie the center taps
together, and drive the motors the way I did the 4-phase motors????

2  Am I going to have to build a new driver board to accommodate the 2-phase
motors.  If so, should I just find some type of stepper control IC?

3  Do you all think that TIP-120's are stout enough to drive these motors?
5 watts doesn't seem like too much of a load on a tip-120, is that correct?
I guess I would need to add some heat sinks, though.

Michael Brown
Instant Net Solutions
http://www.KillerPCs.net

"In the land of the blind, he who has one eye is king"

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2002\02\23@175236 by michael brown

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Update

It turns out that I *can* tie the center taps together.  Once I figured out
the sequencing, I was able to get my driver board to make it go. ;-)  But
I'm still confused as to what is the difference between a 2-phase and a
4-phase vs. uni-polar and bi-polar.  I think I understand the difference
between uni-polar and bi-polar, but I don't get the 2-phase/4-phase thing.
This motor says it is 2-phase, but I am driving it in a uni-polar fashion
(no h-bridge)  Perhaps any 6 (or 5) wire stepper can be driven in either
bi-polar OR uni-polar way???  Perhaps the torque is higher when using it in
a bi-polar way (with h-bridge flipping polarity) since you are using the
full length of the driven coil (as opposed to half the coil energized at a
time) when driving uni-polar)???

The motor did get a little hot, but that's probably due to the fact that I
was using 12V to drive a 6V motor (hey they're cheaper than a new 6V
gel-cell)  With the transistors dissipating twice the power they will have
to at 6V, they still didn't get very warm.  So, I guess that heat sinks
won't be required yet (8 heat sinks cost allot of money)

These things are real stump pullers.  ;-D  I can't believe how much more
torque they have vs. the floppy steppers (these are just a tad bit bigger).
My little creeper bot will really be able to move now.  ;-)

Any ideas on some approximately 6" diameter wheels with 3/16 (5mm) shaft
size?

Sorry so long winded, I'm just trying to provide plenty of information.

Michael Brown
Instant Net Solutions
http://www.KillerPCs.net

"In the land of the blind, he who has one eye is king"

{Original Message removed}

2002\02\23@195913 by Vern Jones

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Michael,

Try this site for a complete tutorial on stepper motors.


http://www.cs.uiowa.edu/~jones/step/index.html

Jones puts it all together in an easy to understand package...

Vern

michael brown wrote:
>
> Update
>
> It turns out that I *can* tie the center taps together.  Once I figured out
> the sequencing, I was able to get my driver board to make it go. ;-)  But
> I'm still confused as to what is the difference between a 2-phase and a
> 4-phase vs. uni-polar and bi-polar.  I think I understand the difference

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2002\02\23@211937 by David P. Harris

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Michael-
Glad things are working out.  I have been playing with floppy steppers, and they
are probably ok for my application, but where did you get the 'real stump
pullers' - I think I could afford $7 each ;-)
David
michael brown wrote:

{Quote hidden}

> {Original Message removed}

2002\02\23@224645 by michael brown

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> Michael-
> Glad things are working out.  I have been playing with floppy steppers,
and they
> are probably ok for my application, but where did you get the 'real stump
> pullers' - I think I could afford $7 each ;-)
> David

I got them from a surplus store here in houston.  They seem to have come
from some type of medical machine.  There is a nifty assembly attached that
with about 15 or 20 little "fingers" in a line.  When the motor turns, the
"fingers" move up and down in a moving sine wave type pattern.  They were
used as a pump in some type of dialysis or bypass machine.

I probably shouldn't have called them stump pullers, but they are
significantly more powerful than the only slightly smaller floppy motors.
They've had these for over a year, and they don't seem to be selling too
fast.  However, some engineer, selling 8052-type development boards just put
together a demo using one of those stepper motors, so they might dry up
quick.  You just never know.

I got them from Electronic Parts Outlet (aka EPO) here in houston.  If you
need, I could get their phone number for you, or even get some and ship them
to you.  They are used and asis, but the two that I got work fine.

BTW, do you know any way to get them to quiet down or to turn more smoothly.
I am already half stepping them, but that is just not as smooth as I'd like.

michael

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2002\02\23@225526 by James Paul

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Hey Michael,

I too am in the Houston area.  Specifically I live in Pecan Grove in
Richmond.    I shop at EPO on Fondren quite often.  Maybe I'll see
you there sometime.



Regards,


Jim
{Original Message removed}

2002\02\23@234632 by Matt Pobursky

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On Sat, 23 Feb 2002 21:43:14 -0600, michael brown wrote:
>
>I got them from a surplus store here in houston.  They seem to
>have come from some type of medical machine.  There is a nifty
>assembly attached that with about 15 or 20 little "fingers" in a
>line.  When the motor turns, the "fingers" move up and down in a
>moving sine wave type pattern.
>They were used as a pump in some type of dialysis or bypass
>machine.
>

I have designed a few of these medical devices -- what you have
is a linear peristaltic pump mechanism from an infusion pump.

A flexible silicone tubing set is fixed in the mechanism and (as
you described) the "fingers" move up and down. As they move, a
segment of fluid is continuosly trapped and squeezed out of the
tube quite precisely. The rate of delivery is set by how fast the
microcontroller drives the fingers up and down.

Matt Pobursky
Maximum Performance Systems

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2002\02\24@002944 by michael brown

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> Hey Michael,
>
> I too am in the Houston area.  Specifically I live in Pecan Grove in
> Richmond.    I shop at EPO on Fondren quite often.  Maybe I'll see
> you there sometime.

Hello Jim,

I live in JV near 290 and the tollway.  Didn't you give a talk about PIC's
at a BVARC meeting?  I was going to go, got side-tracked and missed it.

Anyway, EPO is selling these tiny (55mm*55mm) 8052 based SBC's clipping
along at just over 22Mhz.  The board has a built on ICSP thanks to a PIC
chip.  It seems that the PIC has other tasks also (such as controlling the
contrast on a connected LCD module amongst other things).  It does not have
a boot-loader feature though, since there is no external RAM (kinda weird
for an 8052, huh?).  There is, however, a 4K EEPROM.  It is set up as a
development/learning tool as there are add-on boards that can stack onto the
cpu board.  They have a pre-wired LCD available and a keypad.

I got one because of the small size and partially on impulse cuz it was
right there in front of me. ;-D  I would prefer that it had external ram,
but it is not necessary right now.  At least this way it's kinda like
programming a PIC with only 256 bytes of ram available.  ;-)

hope to meet you sometime

michael

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2002\02\24@021539 by dpharris

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Hi-
WRT smoothing-
There has been some suggestion of using "magic sinewaves" to do this.  This
consists of timing pulses to the steppers such that the result is close to a
sinewave.  I had a go at it, but it did not seem to help that much.  However, My
attempt shouldn't be constued as disproof of concept.  Try here:
http://www.tinaja.com/magsn01.asp
David

michael brown wrote:

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2002\02\24@022831 by dpharris

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Hi-
Lots of stuff on the internet, here's some more:
  * control with a few IC's, and a good explanation of steppers:
    vv.carleton.ca/~neil/robotics/stepper/ttl.html
  * previously mentioned:  http://www.doc.ic.ac.uk/~ih/doc/stepper/
  * stepper controller using 12C509 PIC:
    www.beowulf.demon.co.uk/serial-stepper.html
  * stepper motors for robots: http://www.terra.es/personal4/joan.ilari/
  * stepper motor source, for example:  http://www.futurebots.com/motor.htm
Cheers, David H.

Vern Jones wrote:

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2002\02\25@074208 by Alan B. Pearce

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> Michael-
> Glad things are working out.  I have been playing with floppy steppers,
and they
> are probably ok for my application, but where did you get the 'real stump
> pullers' - I think I could afford $7 each ;-)
> David


One good place to get real "Stump Pullers" is high speed printers. Dot
matrix ones are likely to have two in them (although they are likely to be
different) one for paper feed, and one for carriage movement. Line printers
will also likely have them for paper feed.

I used to like the ones used in Dataproducts printers. The L300, L600,
L900/1000 printers used a hefty motor for paper feed, and there are
thousands of these printers out there, many marketed by OEM's under there
own name/model number. The motors were almost indestructible.

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2002\02\25@101714 by Eoin Ross

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Check out http://www.meci.com - killed many an hour wandering around their third floor - ALL kinds of stuff there

>>> EraseMEn5qmgspam_OUTspamTakeThisOuTAMSAT.ORG 02/23/02 10:43PM >>>
> Michael-
> Glad things are working out.  I have been playing with floppy steppers,
and they are probably ok for my application, but where did you get the 'real stump pullers' - I think I could afford $7 each ;-)
> David

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