Precautions When Connecting An Encoder - Mitsubishi Electric MELSEC Q Series User Manual

4.6.2

Precautions when connecting an encoder

This section describes precautions when connecting an encoder.
(1) Operation of the QD73A1 (deviation counter and feedback pulses)
The deviation counter in the QD73A1 counts up and down.
An addition/subtraction switchover can be processed through the phases of feedback pulses.
When "0: Positive voltage is output when the positioning address increases." is set for "Rotation direction setting"
in the switch setting.
When feedback pulses are input with the phase A leading the
phase B by 90°, the number of command pulses is subtracted.
This input method is for counting positive command pulses when
the speed command is positive voltage (when the motor is rotating
forward).
When feedback pulses are input with the phase B leading the
phase A by 90°, the number of command pulses is added.
This input method is for counting negative command pulses when
the speed command is negative voltage (when the motor is
rotating reverse).
If the sequence of the phase A and phase B is reversed, the number of command pulses and feedback pulses
are counted together. This can cause an excessive error of accumulated pulses, resulting in the stop of the
control.
(a) Switch setting and the encoder
When "1: Negative voltage is output when the positioning address increases." is set for "Rotation direction
setting" in the switch setting, the count process (positive or negative) of the feedback pulses varies depending
on "Feed back pulse addition/subtraction setting" of the switch setting as shown below.
"Rotation direction setting"
0: Positive voltage is output when the
positioning address increases.
1: Negative voltage is output when the
positioning address increases.
Command
pulse
× DIR
Rotation direction setting
When 0 is set: DIR = 1
When 1 is set: DIR = -1
66
Switch setting
"Feed back pulse
addition/subtraction setting"
-
0: Add when the phase A proceeds 90
degrees than phase B.
1: Subtract when the phase A proceeds
90 degrees than phase B.
Deviation
counter
+
+/-
Feedback pulse
addition/
subtraction setting
Multiplication
setting
Feedback pulse
Phase A
Phase B
Phase A
Phase B
When the phase A
proceeds 90 degrees than
phase B
Subtraction
Addition
Subtraction
Analog voltage
D/A
converter
Feedback
Rotation
pulse addition
When the phase A
direction
/subtraction
proceeds 90 degrees
setting
setting
than phase B
0 0 - (subtraction)
0
1
1 - (subtraction)
Feedback pulse
When the phase B
proceeds 90 degrees than
phase A
Addition
Subtraction
Addition
Feedback pulse
When the phase B
proceeds 90 degrees
than phase A
+ (addition)
+ (addition) - (subtraction)
+ (addition)