MID-7604/7602Power Drive 18 ni.com
If the encoder cable length is greater than 10 ft, use encoders with line
driveroutputs for your applications. Power for a +5 V encoder—generated
bya power supply inside the MID-7604/760 2—isavailable on pin 7.
Note If you require other encoder powervoltages, reference an external power supply to
the Digital Ground signal on the 8-pin encoder terminal block.
TheMID-7604/7602 supports differential inputs for Phase A, Phase B, and
Indexsignals. You can easily accommodate encoders with various phase
relationshipsby swapping the signals and/or connecting them to the
invertinginputs as specific applications require. The Index signal must
occurw hen both PhaseA and Phase B signals are low,as shown in
Figure 7. If the Index polarity is inverted,try reversing the Index and Index
signals on differentialencoders or usingt he Index input on single-ended
encoders.
Figure 7 showsthe proper encoder phasing for CW (forward)motor
rotation.
Figure7. Encoder Signal Phasing, CW Rotation
Closed-loop stepper applications require consistent directional polarity
between the motor and encoder for correct operation. The National
Instruments motion control standard directional polarity is as follows:
•Positive= forward = clockwise (C W) facing motor shaft
•Negative= reverse = counter-clockwise (CCW) facing motor shaft
PhaseA
PhaseB
Index