C
ONNECT
STC
S
TO
A
MPS
/M
OTOR
/E
NCODER
4-4
P
C
X
,
S
T
D
,
1
0
4
X
,
C
P
C
I
&
V
6
U
C
o
n
n
ec
ti
o
n
s
to
S
te
p
M
o
to
rs
Connections to Step Motors
Open-Loop Step Motors
The DSP controllers can control step motors in both open-loop (no encoder) and closed-loop
configurations. In the open-loop configuration the step pulse output (connected to the drive) is
fed back into the line receivers and used to keep track of the “actual position.” With open-loop
step configuration selected, the DSP closes the loop internally on a pair of axes. DSP control-
lers are compatible with full, half and micro stepping drives.
Figure 4-3
Typical Open-Loop Step Motor Connections (PCX/CPCI/STD/V6U/104X)
Closed-Loop Step Motors
DSP Series controllers can control step motors with encoder feedback. Closed-loop steps are
controlled by a PID algorithm running on the DSP in real time. The controllers accept TTL-
level (0V to 5V, 40mA max) encoder input from either differential or single-ended encoders.
Differential encoders are preferred due to their excellent noise immunity. The connections for
a single-ended encoder is identical to a differential encoder except that there are no connections
made to channel A- and channel B-. (The A- and B- lines are pulled up internally to 2.5V).
Encoder signals are read in quadrature. Every line on the encoder will produce a rising edge
and a falling edge on channels A+ and B+ which is interpreted by the DSP controller as 4 en-
coder counts.
Connecting closed-loop step motors to the controller is similar to servo motors, except that the
step and direction lines are connected instead of the analog signal. The minimum connections
are:
Step+ (or Step-)
Di (or Direction-)
Signal Ground
Encoder A+ and B+ lines
+5V
M
OTOR
M
OTOR
STC-26
STC-26
12
11
1
1
12
10
Step -
Step +
GND
STEP
DIR
GND
STEP
DIR
S
TEP
D
RIVE
This connection is for step drives that trigger on
the
falling edge
.
This connection is for step drives that trigger on
the
rising edge
.
From
PCX
CPCI
STD
V6U
104X
From
PCX
CPCI
STD
V6U
104X
S
TEP
D
RIVE
T
O
O
PEN
-
LOOP
S
TEP
M
OTORS
GND
Direction
GND
Direction
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