The Auxiliary I/O connector on these models is a standard screw terminal connector and is wired according to the pin-out shown in Table 3-11 and in section 3.6.10, Connection Diagrams (note that these models are available with either DeviceNet or Profibus network connectivity). Because the connections are made to screw terminals, no prefabricated cable is offered for Auxiliary I/O connections for these models.

Detailed descriptions for each signal on the Auxiliary I/O connector are shown in the following table.

Auxiliary I/O Break Out Terminal board (part #44A726268-001) can be used to provide screw terminal interface for the connections. (Applies to 4A and 7A servo models and 5A stepper model only.)

Analog Output (AO)

The hardware analog output is primarily used as a process input to the controller programs, but it can also be used a diagnostic output for various signals used in the tuning and debugging process. The Analog Common pin is used for the signal return. The Analog Output (AO) software parameter allows you to configure this output to represent one of the following signals:

• Actual velocity (AO = VLA)

• Actual output current (AO = CMD)

• Following error (AO = FE)

The output can also be forced to a specific voltage value by setting the AO parameter to the desired voltage from a program, PC terminal emulator, or Motion Developer terminal window. The analog Output value can be queried in the terminal window using the “?” command.

Use 20-28 AWG twisted-pair wire with an overall shield for this signal interface. For best noise immunity connect the shield to the Analog Common pin on the Auxiliary I/O connector. The internal schematic for the analog output circuit is shown below.

Enable Input

The Enable discrete input allows the host controller to enable or disable the power output stage of the controller and reset faults. The Enable input must be active to run the servo motor. This Enable hardware input works in tandem with a logical (software) enable register called the Power Output Stage Enable (POE) register. The POE register will allow current to flow into the motor only when set true and no faults are present on the controller. Since a Lost Enable (LE) fault is generated when this hardware enable input is false, ensure that POE=1, the hardware enable input is true, and all faults have been cleared (RSF register) to activate the power stage of the controller.

The current state of the Enable input can be queried using the Fault Code (FC) register in the terminal window. The Enable input should be connected as shown in the connection diagrams in Section 3.6.10. The internal schematic for the enable input circuit is shown below.

OK Output

The OK discrete output allows the S2K to communicate status information to the host controller. The OK output is active when the controller is enabled and no faults are present. The S2K LED status register will display OK when this output is active. The internal schematic for the OK output circuit is shown below.

Analog Inputs

There are two 12-bit differential analog inputs that support an operating voltage range of ± 10Vdc. These general-purpose inputs can be read as a voltage value in user programs using the AI command. The analog input values can also be queried in the terminal window using the “?” command. Wiring connections should use twisted shielded cable for best noise immunity. Connect the cable and shield as shown in Section 3.6.10, Connection Diagrams.

Auxiliary Encoder Input

The auxiliary encoder input is a flexible input that can be used as a master input for cam or electronic gearing applications, a secondary position monitor, a remote axis position feedback or as secondary position feedback for dual position loop control for the S2K servo controllers. The auxiliary encoder is selected as the master position source for camming by setting the Cam Shaft Position Type (CAT) equal to PSX. The auxiliary encoder is the default command source when gearing is enabled (GRE=1). If the Handwheel Input is enabled (HWE=1), digital inputs 5 and 6 are used for connecting an A/B type hand wheel for use as the gearing command source instead of the auxiliary encoder.

If the Position Feedback Enable is set (PFE=1), the axis position (PSA) is updated from the auxiliary encoder rather than the motor encoder. In addition, when the Position Feedback Numerator (PFN) is non-zero the S2K controller uses a dual position loop mode where the motor encoder is used for the primary position loop and the auxiliary encoder is used for secondary position loop. In this case the auxiliary encoder should be connected to the load to allow the S2K to accurately control the load position without the effects of lost motion from the mechanics. This dual loop arrangement is a very powerful feature that provides excellent servo stability while eliminating the inaccuracy caused by backlash and compliance in the system mechanics. The auxiliary encoder input is connected on the Auxiliary I/O connector for the STI105, SSI104, SSI107, and SSI407 models and to the Pulse Input connector for the SSI216, SSI228, and SSI420 models. Wiring connections should use twisted shielded cable for best noise immunity. Connect the cable and shield as shown in Section 3.6.10, Connection Diagrams. The auxiliary encoder inputs are labeled with “IN_” prefix on these diagrams.

The S2K controller includes an electronic gearing mode that allows the motor to follow a master encoder (follower) or pulse command source (stepper emulator). The Auxiliary Encoder Type (QTX) register configures this input for one of the following signal types:

• Pulse/Direction input

• CCW/CW pulse input

• Quadrature (encoder) input

If an Auxiliary Encoder Input is being driven by a 26LS31 or equivalent differential line driver, it is recommended that a 120-ohm parallel termination resistor be used (please see specifications for RS422 communications for details). If being used in a singled-ended circuit, see the section called “Tie” below.

Note that the S2K Primary Encoder feedback receivers have internal termination resistors.

Note that on the SSI216, SSI228, and SSI420 models, the auxiliary encoder input and the +5Vdc output are located on the Pulse Input connector on the bottom of the controller. The internal schematic for the encoder input circuit is shown below.

NOTE: when the Auxiliary Encoder input is used with a single-ended signal source, see the next section titled “Tie” below.
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