Connecting the encoders, Encoder input circuitry – Adept SmartMotion User Manual

Page 40

Chapter 2 - System Installation

Adept SmartMotion Installation Guide, Rev. C

Connecting the Encoders

Each encoder channel has its own 9-pin D-connector. The connectors are intentionally not
keyed and can be interchanged for diagnostic purposes, provided that no attempt is made
to enable the associated axis. The pin assignment for each connector is detailed in

Table

2-9

. For best protection against noise, use shielded twisted-pair cable. The shield should

encase only those signals associated with that particular encoder channel. A separate
terminal is provided for connection of the shield. To avoid creating a “ground loop,” the
shield should normally be left floating (not connected) at the encoder end, unless the
encoder body is electrically isolated from the equipment it is mounted to.

Encoder Input Circuitry

All incremental-encoder input circuits are identical. Standard hardware configurations of
the sMI6 support RS-422 +5VDC signal levels in a differential mode. Adept strongly
recommends using differential encoders for maximum noise immunity. Using differential
encoders also enables the Encoder failure detection system to function. However, Adept
SmartMotion hardware is compatible with single-ended and open-collector outputs.
Schematics to connect these types of encoders are located in

Figure 2-12

and

Figure 2-13

NOTE: If you use single-ended inputs, say by connecting the encoder's A
signal to the sMI6's “A-” input as in earlier MI6 systems, then you must
now connect the opposite polarity signal, “A+” in this example, to the
encoder and sMI6 power supply common.

If an older MI6-based system is being retrofitted with the sMI6, the connections of any
single-ended encoder signals must be modified in the customer wiring. The unused
differential signal input on A, B or Index, must be connected to the encoder power
common. For example, the standard wiring scheme was to connect the encoder
single-ended A to Adept's A-, the encoder B to B- and encoder Index to Index-. For this
example, the Adept A+, B+, and Index+ signals must be connected to Power Com in the
user wiring, say at the 9-pin connector, for the single-ended encoder to work on the sMI6.
See

Table 2-9

The encoder signals pass directly through the MP6-E to the sMI6 module. All encoder
inputs use RS-422 receivers on the differential inputs.

Figure 2-10

and

Figure 2-11

illustrate the input circuit for each encoder channel. The A, B, and Index signals are then
digitally filtered to improve noise immunity.

Table 2-9. Encoder Channel Pin Assignments (Channel 1 to 6)

Pin Number

Encoder Signal

Pin Number

Encoder Signal

A +