Stepper Motor Basics

B

Bill Bowden

Guest
I have a stepper motor from Airpax, modle C82710 that has 6 wires
connected to 2 windings with a center tap. It's rated at 12 volts, 36
ohms from center tap to the end of the winding, and 7.5 degrees per
step.

I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.

I played around with it, and found I could move the motor shaft one
step at a time by just alternating the connection to either side of
one of the windings with the center tap common. But it only goes so
far and stops, and the second winding was not being used.

So, the question is, what is a proper polarity and timing sequence on
the various connections to continuously move the motor in the same
direction?

-Bill
 
On Apr 13, 2:02 pm, Bill Bowden <wrongaddr...@att.net> wrote:
I have a stepper motor from Airpax, modle C82710 that has 6 wires
connected to 2 windings with a center tap. It's rated at 12 volts, 36
ohms from center tap to the end of the winding, and 7.5 degrees per
step.

I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.

I played around with it, and found I could move the motor shaft one
step at a time by just alternating the connection to either side of
one of the windings with the center tap common. But it only goes so
far and stops, and the second winding was not being used.

So, the question is, what is a proper polarity and timing sequence  on
the various connections to continuously move the motor in the same
direction?
Click to expand...

Look here:

http://en.wikipedia.org/wiki/Stepper_motor

Cheers
 
On Sat, 12 Apr 2008 19:02:05 -0700 (PDT), Bill Bowden
<wrongaddress@att.net> wrote:

I have a stepper motor from Airpax, modle C82710 that has 6 wires
connected to 2 windings with a center tap. It's rated at 12 volts, 36
ohms from center tap to the end of the winding, and 7.5 degrees per
step.

I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.

I played around with it, and found I could move the motor shaft one
step at a time by just alternating the connection to either side of
one of the windings with the center tap common. But it only goes so
far and stops, and the second winding was not being used.

So, the question is, what is a proper polarity and timing sequence on
the various connections to continuously move the motor in the same
direction?
Click to expand...
Sounds like you have a uni-polar stepper there. The simplest way to
drive it is just to use four transistors. Apply your 12 V to the
common and setup the transistors to turn on to provide a ground path
for the desired winding. Sequence them in the order A, B, ~A, ~B.

Once you have that part working, you can look into half-stepping (two
phases on at once) and beefier drive circuits (choppers) that control
the current through the windings for higher torque and speed.

Wikipedia has a pretty good article with additional links.
http://en.wikipedia.org/wiki/Stepper_motor

--
Rich Webb Norfolk, VA
 
On Apr 13, 11:39 pm, Rich Webb <bbew...@mapson.nozirev.ten> wrote:

Wikipedia has a pretty good article with additional links.http://en.wikipedia.org/wiki/Stepper_motor
Click to expand...
Is there an echo in here?

Cheers
 
Or use 2 dpdt toggle switches as a quick visualization tool... switch
them in the order 00 01 11 10 to go one way, reverse switch order to
step the other way.
 
Bill Bowden wrote:
On Apr 13, 4:39 am, Rich Webb <bbew...@mapson.nozirev.ten> wrote:
On Sat, 12 Apr 2008 19:02:05 -0700 (PDT), Bill Bowden



wrongaddr...@att.net> wrote:
I have a stepper motor from Airpax, modle C82710 that has 6 wires
connected to 2 windings with a center tap. It's rated at 12 volts, 36
ohms from center tap to the end of the winding, and 7.5 degrees per
step.
I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.
I played around with it, and found I could move the motor shaft one
step at a time by just alternating the connection to either side of
one of the windings with the center tap common. But it only goes so
far and stops, and the second winding was not being used.
So, the question is, what is a proper polarity and timing sequence on
the various connections to continuously move the motor in the same
direction?
Sounds like you have a uni-polar stepper there. The simplest way to
drive it is just to use four transistors. Apply your 12 V to the
common and setup the transistors to turn on to provide a ground path
for the desired winding. Sequence them in the order A, B, ~A, ~B.

Once you have that part working, you can look into half-stepping (two
phases on at once) and beefier drive circuits (choppers) that control
the current through the windings for higher torque and speed.

Wikipedia has a pretty good article with additional links.http://en.wikipedia.org/wiki/Stepper_motor

--
Rich Webb Norfolk, VA


Thanks, but I'm not sure of the sequence A,B,-A,-B. Suppose I have
both center taps connected to +12 and the other 4 lines are connected
to transistors. The problem is which side of which winding should I
start with? And will the next transistor supply a ground to the other
side of the same winding? An then there is a phase problem dealing
with the second winding? How do I know which side of the second
winding to ground next?

-Bill
Playing with stepper motors I did the following:
Click to expand...
attach both centre taps to 5 volts, and attach
a 10-15 cm piece of wood(I used a shaslik stick)
to the stepper motor axis.
Now ground one of the four wires,and mark the place
pointed at by the stick. Use your hand to damp the motion,
and in this way you get 4 marks close together.
Now just check which wire belongs to one of those
positions, and you know in which order you have to power them.
I connected a 4 channel buffer IC to them, and connected
the buffer to my computers printer port.
I also put 4 leds on those outputs, to be able to
see what my printerport did to those inputs.
For medium force, just energise them 1-2-3-4-1-2-3-4 etc.
For high force, use 12-23-34-41-12-23-34-41 etcetera.
 
On Apr 13, 4:39 am, Rich Webb <bbew...@mapson.nozirev.ten> wrote:
On Sat, 12 Apr 2008 19:02:05 -0700 (PDT), Bill Bowden



wrongaddr...@att.net> wrote:
I have a stepper motor from Airpax, modle C82710 that has 6 wires
connected to 2 windings with a center tap. It's rated at 12 volts, 36
ohms from center tap to the end of the winding, and 7.5 degrees per
step.

I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.

I played around with it, and found I could move the motor shaft one
step at a time by just alternating the connection to either side of
one of the windings with the center tap common. But it only goes so
far and stops, and the second winding was not being used.

So, the question is, what is a proper polarity and timing sequence on
the various connections to continuously move the motor in the same
direction?

Sounds like you have a uni-polar stepper there. The simplest way to
drive it is just to use four transistors. Apply your 12 V to the
common and setup the transistors to turn on to provide a ground path
for the desired winding. Sequence them in the order A, B, ~A, ~B.

Once you have that part working, you can look into half-stepping (two
phases on at once) and beefier drive circuits (choppers) that control
the current through the windings for higher torque and speed.

Wikipedia has a pretty good article with additional links.http://en.wikipedia.org/wiki/Stepper_motor

--
Rich Webb Norfolk, VA
Click to expand...

Thanks, but I'm not sure of the sequence A,B,-A,-B. Suppose I have
both center taps connected to +12 and the other 4 lines are connected
to transistors. The problem is which side of which winding should I
start with? And will the next transistor supply a ground to the other
side of the same winding? An then there is a phase problem dealing
with the second winding? How do I know which side of the second
winding to ground next?

-Bill
 
On Apr 13, 5:38 pm, Sjouke Burry <burrynulnulf...@ppllaanneett.nnlll>
wrote:
Bill Bowden wrote:
On Apr 13, 4:39 am, Rich Webb <bbew...@mapson.nozirev.ten> wrote:
On Sat, 12 Apr 2008 19:02:05 -0700 (PDT), Bill Bowden

wrongaddr...@att.net> wrote:
I have a stepper motor from Airpax, modle C82710 that has 6 wires
connected to 2 windings with a center tap. It's rated at 12 volts, 36
ohms from center tap to the end of the winding, and 7.5 degrees per
step.
I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.
I played around with it, and found I could move the motor shaft one
step at a time by just alternating the connection to either side of
one of the windings with the center tap common. But it only goes so
far and stops, and the second winding was not being used.
So, the question is, what is a proper polarity and timing sequence on
the various connections to continuously move the motor in the same
direction?
Sounds like you have a uni-polar stepper there. The simplest way to
drive it is just to use four transistors. Apply your 12 V to the
common and setup the transistors to turn on to provide a ground path
for the desired winding. Sequence them in the order A, B, ~A, ~B.

Once you have that part working, you can look into half-stepping (two
phases on at once) and beefier drive circuits (choppers) that control
the current through the windings for higher torque and speed.

Wikipedia has a pretty good article with additional links.http://en.wikipedia.org/wiki/Stepper_motor

--
Rich Webb Norfolk, VA

Thanks, but I'm not sure of the sequence A,B,-A,-B. Suppose I have
both center taps connected to +12 and the other 4 lines are connected
to transistors. The problem is which side of which winding should I
start with? And will the next transistor supply a ground to the other
side of the same winding? An then there is a phase problem dealing
with the second winding? How do I know which side of the second
winding to ground next?

-Bill

Playing with stepper motors I did the following:
attach both centre taps to 5 volts, and attach
a 10-15 cm piece of wood(I used a shaslik stick)
to the stepper motor axis.
Now ground one of the four wires,and mark the place
pointed at by the stick. Use your hand to damp the motion,
and in this way you get 4 marks close together.
Now just check which wire belongs to one of those
positions, and you know in which order you have to power them.
I connected a 4 channel buffer IC to them, and connected
the buffer to my computers printer port.
I also put 4 leds on those outputs, to be able to
see what my printerport did to those inputs.
For medium force, just energise them 1-2-3-4-1-2-3-4 etc.
For high force, use 12-23-34-41-12-23-34-41 etcetera.
Click to expand...

Yes, I drew a little line on the shaft to watch the position and
connected the 4 lines to push button switches so I could ground them
in any order. After a few tries, I found a sequence that keeps moving
the motor the same way. Haven't figured out how to reverse it yet, but
it's a fun game pushing switches to see which way the motor moves.

-Bill
 
On Sat, 12 Apr 2008 19:02:05 -0700 (PDT) in sci.electronics.basics,
Bill Bowden <wrongaddress@att.net> wrote,
I'm not too familiar with stepper motors, but understand the shaft can
be moved in either direction one step at a time. I read some articles
on Google but couldn't find any that showed the necessary signals and
timing to rotate the motor continously in one direction.
Click to expand...
Still the best: Jones on Stepping Motors
http://www.cs.uiowa.edu/~jones/step/

..
 
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