Panasonic MSM (and Fanuc SL) motors with MFE2500P8NB Encoders

Motor/Feedback Description –

The Fanuc SL series motors appear to have the same feedback and same alignment as the Panasonic MSM motors, so in this discussion we will not distinguish one from the other.

The newer MFE2500P8NX encoder is a purely serial encoder that is supported with our MFE test software, however it should not be confused with the legacy MFE2500P8NB encoder that has incremental outputs.  In this document, we are discussing the incremental encoder. It is a 2,500 pulse/rev (10,000 count/rev) incremental encoder with standard A, B, and Z channels, but it also has a serial RX channel. The serial channel provides encoded commutation signals, but our current tester software does not support using this RX channel. However, the A, B, and Z incremental signals can be used to check and set commutation with the TI-5000JX and to run the motor with the TI-3000JX. Some suggestions on checking the RX channel signals will be provided later in this document.

The TI-5053 cable is compatible with this feedback device using the 15 pin AMP connector.

The following information is known to be correct for a Panasonic MSM042A1G and a Fanuc C800SLM075N2XE25B motor. It undoubtedly extends to other similar motors, but these were the
motors used to get the information. You should verify for yourself that this information is usable
for any similar motor you may have. These motors were 8 poles with a forward armature direction
of CW at the drive shaft end. Refer to the TI-5053 cable for feedback pinouts. The armature
connections for the 4 pin and 2 pin AMP connectors were as follows:

Pin       Function            Color
1          U                        RED
2          V                        WHI
3          W                       BLK
4          GND                   GRN
1           24V BRK            YEL
2           24V BRK            YEL

Alignment –

Lockup Polarity              Electrical Angle        Comm Signals (Decoded Serial Stream using Scope)

U        V         W                                               U       V       W

+         -                          120E                          H>L  H       L

+                    -               180E                          L        H       L>H

-                      +              0E                             H       L        H>L

TI-3000JX Setup –

Feedback Manufacturer = Generic Encoder
Counts/rev = 10,000
Poles = 8
Direction = S
+U –V Lockup Angle = 120E degrees

RX Channel Serial Data –

Along with the A, B, Z and complement lines, these encoders also have a RX and RX* lines. These lines produce a U, V, W commutation type pattern as 8 bit serial data. At this time there is no tester support for these lines, however, they produce data all the time that can be observed by connecting a scope. The bit pattern can be seen to change as the encoder is rotated. It would be good to check for activity on these lines until support can be developed for these signals.

The basic idea is similar to the Yaskawa C Channel encoders in that the three commutation signals are encoded onto one pair of lines. However there are enough differences that this signal cannot be decoded using Yaskawa C Channel support. 

The signal on the RX line is described as follows:

1. The signal idle state is HI.
2. The data bit time is 1 µS.
3. There are 8 bits of data as follows: Start bit (always goes LO), W*, U*, V*, V, U, W, parity.
4. The time from one start bit to the next is 12 µS. This means that the data word takes 8 µS and the idle time is 4 µS.

At a minimum, you will probably want to put a scope on the RX and RX* lines to verify that the signals are present. You will also be able to see that they are the complement states of each other.

If you are really industrious, you can try to visually decode the states as described in step 3 above and verify the commutation states at the lockup points as shown in the alignment information above.