Re:Mesa 7i77 differencial encoder connection.

I have ordered some 5i25 + 7i77 plug-n-go bundle. I was going through the manual of 7i77 and saw that their encoder connectors have 8 pins for each encoder while my servo encoder provides 15pin connection.

My motor's encoder pins are as below.

12 Power supply(5V) +5V
13 Public ground 0V
1 Encoder A+ input A+
6 Encoder A- input A-
2 Encoder B+ input B+
7 Encoder B- input B-
3 Encoder Z+ input Z+
8 Encoder Z- input Z-
4 Encoder U+ input U+
9 Encoder U- input U-
5 Encoder V+ input V+
10 Encoder V- input V-
14 Encoder W+ input W+
15 Encoder W- input W-
11 Inhibit ground FG


While 7i77 provides following.

1 QA0 TO 7I77
2 /QA0 TO 7I77
3 GND FROM 7I77
4 QB0 TO 7I77
5 /QB0 TO 7I77
6 +5V FROM 7I77
7 IDX0 TO 7I77
8 /IDX0 TO 7I77

Does one set go to the drive and one set to the controller?

I am afraid I don't know! The whole connection comes through a multi-cored cable and goes directly to the driver via serial cable type connector. But from Driver's output, there is A+,A-,B+,B-,Z+,Z- and GND and ZOC. Total eight connector output they provide.

John !
I think it's the same thing as you asked. driver provides one set of output to controller. But is it a good idea to take feedback from driver ? and not from encoder directly ?

The drive needs the U,V,W wires for motor commutation. Its probably best to use the drives A,B,Z outputs so you dont have to "tee" any signals. Depending in the drive, these encoder outpus may just be buffered copies of the encoder inputs or they may be scaled by the drives DSP.

I appreciate you all ! Thanks.

Now it becomes clear that I should use drives output as an encoder feedback.

Thanks again.

ABZ are the encoder lines, 1000+ pulses per rev. Incremental quadrature + Index
UVW are the Hall sensors, 6 unique patterns per rev, low resolution but absolute position.

ABZ are used for positioning, UVW purely so the drive knows which coils need power as the motor rotates.

Wonderful information. I appreciate your knowledge andypugh.