<s>
A	O
stepper	B-Algorithm
motor	I-Algorithm
,	O
also	O
known	O
as	O
step	B-Algorithm
motor	I-Algorithm
or	O
stepping	B-Algorithm
motor	I-Algorithm
,	O
is	O
a	O
brushless	O
DC	O
electric	O
motor	O
that	O
divides	O
a	O
full	O
rotation	O
into	O
a	O
number	O
of	O
equal	O
steps	O
.	O
</s>
<s>
The	O
motor	O
's	O
position	O
can	O
be	O
commanded	O
to	O
move	O
and	O
hold	O
at	O
one	O
of	O
these	O
steps	O
without	O
any	O
position	B-Algorithm
sensor	I-Algorithm
for	O
feedback	O
(	O
an	O
open-loop	O
controller	O
)	O
,	O
as	O
long	O
as	O
the	O
motor	O
is	O
correctly	O
sized	O
to	O
the	O
application	O
in	O
respect	O
to	O
torque	B-General_Concept
and	O
speed	O
.	O
</s>
<s>
Switched	O
reluctance	O
motors	O
are	O
very	O
large	O
stepping	B-Algorithm
motors	I-Algorithm
with	O
a	O
reduced	O
pole	O
count	O
,	O
and	O
generally	O
are	O
closed-loop	O
commutated	O
.	O
</s>
<s>
The	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
known	O
for	O
its	O
property	O
of	O
converting	O
a	O
train	O
of	O
input	O
pulses	O
(	O
typically	O
square	O
waves	O
)	O
into	O
a	O
precisely	O
defined	O
increment	O
in	O
the	O
shaft	O
’s	O
rotational	O
position	O
.	O
</s>
<s>
Stepper	B-Algorithm
motors	I-Algorithm
effectively	O
have	O
multiple	O
"	O
toothed	O
"	O
electromagnets	O
arranged	O
as	O
a	O
stator	O
around	O
a	O
central	O
rotor	O
,	O
a	O
gear-shaped	O
piece	O
of	O
iron	O
.	O
</s>
<s>
The	O
electromagnets	O
are	O
energized	O
by	O
an	O
external	O
driver	O
circuit	O
or	O
a	O
micro	B-Architecture
controller	I-Architecture
.	O
</s>
<s>
The	O
number	O
of	O
groups	O
is	O
chosen	O
by	O
the	O
designer	O
of	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
has	O
two	O
groups	O
identified	O
as	O
A	O
or	O
B	O
,	O
and	O
ten	O
electromagnets	O
in	O
total	O
,	O
then	O
the	O
grouping	O
pattern	O
would	O
be	O
ABABABABAB	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
stepper	B-Algorithm
motors	I-Algorithm
with	O
more	O
phases	O
typically	O
have	O
more	O
wires	O
(	O
or	O
leads	O
)	O
to	O
control	O
the	O
motor	O
.	O
</s>
<s>
There	O
are	O
three	O
main	O
types	O
of	O
stepper	B-Algorithm
motors	I-Algorithm
:	O
</s>
<s>
This	O
detent	O
has	O
a	O
predictable	O
spring	O
rate	O
and	O
specified	O
torque	B-General_Concept
limit	O
;	O
slippage	O
occurs	O
if	O
the	O
limit	O
is	O
exceeded	O
.	O
</s>
<s>
If	O
current	O
is	O
removed	O
a	O
lesser	O
detent	O
still	O
remains	O
,	O
therefore	O
holding	O
shaft	O
position	O
against	O
spring	O
or	O
other	O
torque	B-General_Concept
influences	O
.	O
</s>
<s>
There	O
are	O
two	O
basic	O
winding	O
arrangements	O
for	O
the	O
electromagnetic	O
coils	O
in	O
a	O
two	O
phase	O
stepper	B-Algorithm
motor	I-Algorithm
:	O
bipolar	O
and	O
unipolar	O
.	O
</s>
<s>
A	O
unipolar	O
stepper	B-Algorithm
motor	I-Algorithm
has	O
one	O
winding	O
with	O
center	O
tap	O
per	O
phase	O
.	O
</s>
<s>
Since	O
in	O
this	O
arrangement	O
a	O
magnetic	O
pole	O
can	O
be	O
reversed	O
without	O
switching	O
the	O
polarity	O
of	O
the	O
common	O
wire	O
,	O
the	O
commutation	O
circuit	O
can	O
be	O
simply	O
a	O
single	O
switching	O
transistor	B-Application
for	O
each	O
half	O
winding	O
.	O
</s>
<s>
A	O
microcontroller	B-Architecture
or	O
stepper	B-Algorithm
motor	I-Algorithm
controller	O
can	O
be	O
used	O
to	O
activate	O
the	O
drive	O
transistors	B-Application
in	O
the	O
right	O
order	O
,	O
and	O
this	O
ease	O
of	O
operation	O
makes	O
unipolar	O
motors	O
popular	O
with	O
hobbyists	O
;	O
they	O
are	O
probably	O
the	O
cheapest	O
way	O
to	O
get	O
precise	O
angular	O
movements	O
.	O
</s>
<s>
A	O
quick	O
way	O
to	O
determine	O
if	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
working	O
is	O
to	O
short	O
circuit	O
every	O
two	O
pairs	O
and	O
try	O
turning	O
the	O
shaft	O
.	O
</s>
<s>
A	O
typical	O
driving	O
pattern	O
for	O
a	O
two	O
coil	O
bipolar	O
stepper	B-Algorithm
motor	I-Algorithm
would	O
be	O
:	O
A+	O
B+	O
A−	O
B−	O
.	O
</s>
<s>
A	O
unipolar	O
motor	O
has	O
twice	O
the	O
amount	O
of	O
wire	O
in	O
the	O
same	O
space	O
,	O
but	O
only	O
half	O
used	O
at	O
any	O
point	O
in	O
time	O
,	O
hence	O
is	O
50%	O
efficient	O
(	O
or	O
approximately	O
70%	O
of	O
the	O
torque	B-General_Concept
output	O
available	O
)	O
.	O
</s>
<s>
Though	O
a	O
bipolar	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
more	O
complicated	O
to	O
drive	O
,	O
the	O
abundance	O
of	O
driver	O
chips	O
means	O
this	O
is	O
much	O
less	O
difficult	O
to	O
achieve	O
.	O
</s>
<s>
Multi-phase	O
stepper	B-Algorithm
motors	I-Algorithm
with	O
many	O
phases	O
tend	O
to	O
have	O
much	O
lower	O
levels	O
of	O
vibration	O
.	O
</s>
<s>
Stepper	B-Algorithm
motor	I-Algorithm
performance	O
is	O
strongly	O
dependent	O
on	O
the	O
driver	O
circuit	O
.	O
</s>
<s>
Torque	B-General_Concept
curves	O
may	O
be	O
extended	O
to	O
greater	O
speeds	O
if	O
the	O
stator	O
poles	O
can	O
be	O
reversed	O
more	O
quickly	O
,	O
the	O
limiting	O
factor	O
being	O
a	O
combination	O
of	O
the	O
winding	O
inductance	O
.	O
</s>
<s>
However	O
,	O
it	O
is	O
winding	O
current	O
,	O
not	O
voltage	O
that	O
applies	O
torque	B-General_Concept
to	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
shaft	O
.	O
</s>
<s>
Thus	O
when	O
controlled	O
by	O
a	O
constant	O
voltage	O
drive	O
,	O
the	O
maximum	O
speed	O
of	O
a	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
limited	O
by	O
its	O
inductance	O
since	O
at	O
some	O
speed	O
,	O
the	O
voltage	O
U	O
will	O
be	O
changing	O
faster	O
than	O
the	O
current	O
I	O
can	O
keep	O
up	O
.	O
</s>
<s>
a	O
10mH	O
inductance	O
with	O
2	O
ohms	O
resistance	O
will	O
take	O
5ms	O
to	O
reach	O
approx	O
2/3	O
of	O
maximum	O
torque	B-General_Concept
or	O
around	O
24ms	O
to	O
reach	O
99%	O
of	O
max	O
torque	B-General_Concept
)	O
.	O
</s>
<s>
To	O
obtain	O
high	O
torque	B-General_Concept
at	O
high	O
speeds	O
requires	O
a	O
large	O
drive	O
voltage	O
with	O
a	O
low	O
resistance	O
and	O
low	O
inductance	O
.	O
</s>
<s>
Chopper	O
drive	O
circuits	O
are	O
most	O
often	O
used	O
with	O
two-winding	O
bipolar	O
motors	O
,	O
the	O
two	O
windings	O
being	O
driven	O
independently	O
to	O
provide	O
a	O
specific	O
motor	O
torque	B-General_Concept
CW	O
or	O
CCW	O
.	O
</s>
<s>
This	O
requires	O
additional	O
electronics	O
to	O
sense	O
winding	O
currents	O
,	O
and	O
control	O
the	O
switching	O
,	O
but	O
it	O
allows	O
stepper	B-Algorithm
motors	I-Algorithm
to	O
be	O
driven	O
with	O
higher	O
torque	B-General_Concept
at	O
higher	O
speeds	O
than	O
L/R	O
drives	O
.	O
</s>
<s>
A	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
a	O
polyphase	O
AC	O
synchronous	O
motor	O
(	O
see	O
Theory	O
below	O
)	O
,	O
and	O
it	O
is	O
ideally	O
driven	O
by	O
sinusoidal	O
current	O
.	O
</s>
<s>
It	O
has	O
the	O
same	O
number	O
of	O
steps	O
as	O
the	O
full-step	O
drive	O
,	O
but	O
the	O
motor	O
will	O
have	O
significantly	O
less	O
torque	B-General_Concept
than	O
rated	O
.	O
</s>
<s>
Two	O
phases	O
are	O
always	O
on	O
so	O
the	O
motor	O
will	O
provide	O
its	O
maximum	O
rated	O
torque	B-General_Concept
.	O
</s>
<s>
Wave	O
drive	O
and	O
single	O
phase	O
full	O
step	O
are	O
both	O
one	O
and	O
the	O
same	O
,	O
with	O
same	O
number	O
of	O
steps	O
but	O
difference	O
in	O
torque	B-General_Concept
.	O
</s>
<s>
The	O
motor	O
also	O
has	O
less	O
torque	B-General_Concept
(	O
approx	O
70%	O
)	O
at	O
the	O
full-step	O
position	O
(	O
where	O
only	O
a	O
single	O
phase	O
is	O
on	O
)	O
.	O
</s>
<s>
Step	O
size	O
reduction	O
is	O
an	O
important	O
step	B-Algorithm
motor	I-Algorithm
feature	O
and	O
a	O
fundamental	O
reason	O
for	O
their	O
use	O
in	O
positioning	O
.	O
</s>
<s>
Example	O
:	O
many	O
modern	O
hybrid	O
step	B-Algorithm
motors	I-Algorithm
are	O
rated	O
such	O
that	O
the	O
travel	O
of	O
every	O
full	O
step	O
(	O
example	O
1.8	O
degrees	O
per	O
full	O
step	O
or	O
200	O
full	O
steps	O
per	O
revolution	O
)	O
will	O
be	O
within	O
3%	O
or	O
5%	O
of	O
the	O
travel	O
of	O
every	O
other	O
full	O
step	O
,	O
as	O
long	O
as	O
the	O
motor	O
is	O
operated	O
within	O
its	O
specified	O
operating	O
ranges	O
.	O
</s>
<s>
A	O
step	B-Algorithm
motor	I-Algorithm
can	O
be	O
viewed	O
as	O
a	O
synchronous	O
AC	O
motor	O
with	O
the	O
number	O
of	O
poles	O
(	O
on	O
both	O
rotor	O
and	O
stator	O
)	O
increased	O
,	O
taking	O
care	O
that	O
they	O
have	O
no	O
common	O
denominator	O
.	O
</s>
<s>
To	O
achieve	O
full	O
rated	O
torque	B-General_Concept
,	O
the	O
coils	O
in	O
a	O
stepper	B-Algorithm
motor	I-Algorithm
must	O
reach	O
their	O
full	O
rated	O
current	O
during	O
each	O
step	O
.	O
</s>
<s>
Winding	O
inductance	O
and	O
counter-EMF	O
generated	O
by	O
a	O
moving	O
rotor	O
tend	O
to	O
resist	O
changes	O
in	O
drive	O
current	O
,	O
so	O
that	O
as	O
the	O
motor	O
speeds	O
up	O
,	O
less	O
and	O
less	O
time	O
is	O
spent	O
at	O
full	O
current	O
—	O
thus	O
reducing	O
motor	O
torque	B-General_Concept
.	O
</s>
<s>
As	O
speeds	O
further	O
increase	O
,	O
the	O
current	O
will	O
not	O
reach	O
the	O
rated	O
value	O
,	O
and	O
eventually	O
the	O
motor	O
will	O
cease	O
to	O
produce	O
torque	B-General_Concept
.	O
</s>
<s>
This	O
is	O
the	O
measure	O
of	O
the	O
torque	B-General_Concept
produced	O
by	O
a	O
stepper	B-Algorithm
motor	I-Algorithm
when	O
it	O
is	O
operated	O
without	O
an	O
acceleration	O
state	O
.	O
</s>
<s>
At	O
low	O
speeds	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
can	O
synchronize	O
itself	O
with	O
an	O
applied	O
step	O
frequency	O
,	O
and	O
this	O
pull-in	O
torque	B-General_Concept
must	O
overcome	O
friction	O
and	O
inertia	O
.	O
</s>
<s>
The	O
stepper	B-Algorithm
motor	I-Algorithm
pull-out	O
torque	B-General_Concept
is	O
measured	O
by	O
accelerating	O
the	O
motor	O
to	O
the	O
desired	O
speed	O
and	O
then	O
increasing	O
the	O
torque	B-General_Concept
loading	O
until	O
the	O
motor	O
stalls	O
or	O
misses	O
steps	O
.	O
</s>
<s>
This	O
measurement	O
is	O
taken	O
across	O
a	O
wide	O
range	O
of	O
speeds	O
and	O
the	O
results	O
are	O
used	O
to	O
generate	O
the	O
stepper	B-Algorithm
motor	I-Algorithm
's	O
dynamic	O
performance	O
curve	O
.	O
</s>
<s>
A	O
designer	O
may	O
include	O
a	O
safety	O
factor	O
between	O
the	O
rated	O
torque	B-General_Concept
and	O
the	O
estimated	O
full	O
load	O
torque	B-General_Concept
required	O
for	O
the	O
application	O
.	O
</s>
<s>
Synchronous	O
electric	O
motors	O
using	O
permanent	O
magnets	O
have	O
a	O
resonant	O
position	O
holding	O
torque	B-General_Concept
(	O
called	O
detent	O
torque	B-General_Concept
or	O
cogging	O
,	O
and	O
sometimes	O
included	O
in	O
the	O
specifications	O
)	O
when	O
not	O
driven	O
electrically	O
.	O
</s>
<s>
Stepper	B-Algorithm
motors	I-Algorithm
have	O
a	O
natural	O
frequency	O
of	O
operation	O
.	O
</s>
<s>
Stepper	B-Algorithm
motors	I-Algorithm
 '	O
nameplates	O
typically	O
give	O
only	O
the	O
winding	O
current	O
and	O
occasionally	O
the	O
voltage	O
and	O
winding	O
resistance	O
.	O
</s>
<s>
These	O
figures	O
can	O
be	O
helpful	O
for	O
more	O
in-depth	O
electronics	O
design	O
,	O
when	O
deviating	O
from	O
standard	O
supply	O
voltages	O
,	O
adapting	O
third	O
party	O
driver	O
electronics	O
,	O
or	O
gaining	O
insight	O
when	O
choosing	O
between	O
motor	O
models	O
with	O
otherwise	O
similar	O
size	O
,	O
voltage	O
,	O
and	O
torque	B-General_Concept
specifications	O
.	O
</s>
<s>
A	O
stepper	O
's	O
low-speed	O
torque	B-General_Concept
will	O
vary	O
directly	O
with	O
current	O
.	O
</s>
<s>
How	O
quickly	O
the	O
torque	B-General_Concept
falls	O
off	O
at	O
faster	O
speeds	O
depends	O
on	O
the	O
winding	O
inductance	O
and	O
the	O
drive	O
circuitry	O
it	O
is	O
attached	O
to	O
,	O
especially	O
the	O
driving	O
voltage	O
.	O
</s>
<s>
Steppers	O
should	O
be	O
sized	O
according	O
to	O
published	O
torque	B-General_Concept
curve	O
,	O
which	O
is	O
specified	O
by	O
the	O
manufacturer	O
at	O
particular	O
drive	O
voltages	O
or	O
using	O
their	O
own	O
drive	O
circuitry	O
.	O
</s>
<s>
Dips	O
in	O
the	O
torque	B-General_Concept
curve	O
suggest	O
possible	O
resonances	O
,	O
whose	O
impact	O
on	O
the	O
application	O
should	O
be	O
understood	O
by	O
designers	O
.	O
</s>
<s>
Step	B-Algorithm
motors	I-Algorithm
adapted	O
to	O
harsh	O
environments	O
are	O
often	O
referred	O
to	O
as	O
IP65	O
rated	O
.	O
</s>
<s>
The	O
US	O
National	O
Electrical	O
Manufacturers	O
Association	O
(	O
NEMA	O
)	O
standardises	O
various	O
dimensions	O
,	O
marking	O
and	O
other	O
aspects	O
of	O
stepper	B-Algorithm
motors	I-Algorithm
,	O
in	O
NEMA	O
standard	O
(	O
NEMA	O
ICS	O
16-2001	O
)	O
.	O
</s>
<s>
NEMA	O
stepper	B-Algorithm
motors	I-Algorithm
are	O
labeled	O
by	O
faceplate	O
size	O
,	O
NEMA	O
17	O
being	O
a	O
stepper	B-Algorithm
motor	I-Algorithm
with	O
a	O
faceplate	O
and	O
dimensions	O
given	O
in	O
inches	O
.	O
</s>
<s>
There	O
are	O
further	O
specifiers	O
to	O
describe	O
stepper	B-Algorithm
motors	I-Algorithm
,	O
and	O
such	O
details	O
may	O
be	O
found	O
in	O
the	O
ICS	O
16-2001	O
standard	O
.	O
</s>
<s>
Computer	O
controlled	O
stepper	B-Algorithm
motors	I-Algorithm
are	O
a	O
type	O
of	O
motion-control	B-Algorithm
positioning	O
system	O
.	O
</s>
<s>
In	O
the	O
field	O
of	O
lasers	O
and	O
optics	B-Algorithm
they	O
are	O
frequently	O
used	O
in	O
precision	O
positioning	O
equipment	O
such	O
as	O
linear	B-Algorithm
actuators	I-Algorithm
,	O
linear	O
stages	O
,	O
rotation	O
stages	O
,	O
goniometers	O
,	O
and	O
mirror	O
mounts	O
.	O
</s>
<s>
Commercially	O
,	O
stepper	B-Algorithm
motors	I-Algorithm
are	O
used	O
in	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
flatbed	O
scanners	O
,	O
computer	O
printers	O
,	O
plotters	B-Operating_System
,	O
slot	O
machines	O
,	O
image	B-Application
scanners	I-Application
,	O
compact	O
disc	O
drives	O
,	O
intelligent	O
lighting	O
,	O
camera	O
lenses	O
,	O
CNC	O
machines	O
,	O
and	O
3D	O
printers	O
.	O
</s>
<s>
A	O
stepper	B-Algorithm
motor	I-Algorithm
system	O
consists	O
of	O
three	O
basic	O
elements	O
,	O
often	O
combined	O
with	O
some	O
type	O
of	O
user	O
interface	O
(	O
host	O
computer	O
,	O
PLC	O
or	O
dumb	O
terminal	O
)	O
:	O
</s>
<s>
Indexers	O
The	O
indexer	O
(	O
or	O
controller	O
)	O
is	O
a	O
microprocessor	B-Architecture
capable	O
of	O
generating	O
step	O
pulses	O
and	O
direction	O
signals	O
for	O
the	O
driver	O
.	O
</s>
<s>
Not	O
all	O
drivers	O
are	O
suitable	O
to	O
run	O
all	O
motors	O
,	O
so	O
when	O
designing	O
a	O
motion	B-Algorithm
control	I-Algorithm
system	I-Algorithm
,	O
the	O
driver	O
selection	O
process	O
is	O
critical	O
.	O
</s>
<s>
Stepper	B-Algorithm
motors	I-Algorithm
The	O
stepper	B-Algorithm
motor	I-Algorithm
is	O
an	O
electromagnetic	O
device	O
that	O
converts	O
digital	O
pulses	O
into	O
mechanical	O
shaft	O
rotation	O
.	O
</s>
<s>
Precise	O
positioning	O
and	O
repeatability	O
of	O
movement	O
,	O
since	O
good	O
stepper	B-Algorithm
motors	I-Algorithm
have	O
an	O
accuracy	O
of	O
3	O
–	O
5%	O
of	O
a	O
step	O
and	O
this	O
error	O
is	O
non-cumulative	O
from	O
one	O
step	O
to	O
the	O
next	O
.	O
</s>
<s>
Resonance	O
effect	O
often	O
exhibited	O
at	O
low	O
speeds	O
and	O
decreasing	O
torque	B-General_Concept
with	O
increasing	O
speed	O
.	O
</s>
