Inputs And Outputs; Allowed Sensor Types On Digital Inputs; Inputs; Safe Option Monitoring (So Mon) - Danfoss VLT Safety Option MCB 152 Installation Manual

Installation Guide | VLT®Safety Option MCB 152

3.9 Inputs and Outputs

3.9.1 Allowed Sensor Types on Digital Inputs

The following list describes how digital inputs are activate depending on sensor types.
• NCNC: A digital input is active when there is 0 V at both channels of the input.
• Antivalent switches: A digital input is active only when there is 0 V at channel A and 24 V at channel B.
• NC: The functionality is similar to NCNC.
Sensors with 2 NO switches are not applicable.
The safe digital inputs are configured for both directly connecting safety sensors, for example emergency stop control devices or light
curtains, and for connecting preprocessing safety relays, for example, safe controls. See examples of connecting the safe digital input,
in accordance with EN ISO 13849-1 and EN IEC 62061 in

3.9.2 Inputs

The dual-channel digital inputs are used to activate the safety functions. 1 or both digital inputs can be disabled.
DI 1 can have 1 of the following functions:
• STO: Safe Torque Off.
• SO Mon: Safe option monitoring through the safe fieldbus.
DI2 can have 1 of the following functions:
• STO: Safe Torque Off.
• SO Mon: Safe option monitoring.
• Reset: Extra safe input to reset the safety option after a fault, or after deactivating a safety function on input DI1.

3.9.3 Safe Option Monitoring (SO Mon)

The PLC can use the digital inputs of the safety option as safe inputs. If a digital input is set to Safe Option Monitoring (SO Mon), the
safety option maintains all signal checks (discrepancy, and so on) on the digital inputs, but the safety option does not activate safety
functions if a signal changes. All safety logic is carried out by the PLC.

3.9.4 Output

S37 is the safe, single-channel output that goes to the STO input of the drive. For information about the events that trigger STO, see
Safe Torque Off - STO.

3.9.5 Signal Filtering

If a sensor with NCNC or antivalent is selected, the safety option checks the signals of the safe digital input for consistency. If NCNC is
selected, consistent signals at both inputs always assume the same signal state (high or low). If antivalent is selected, it checks the right
state of each input.
With electromechanical sensors (for example, emergency stop buttons or door switches), the 2 sensor switches never switch at the
same time (discrepancy). A long-term discrepancy points towards a fault in the wiring of a safe input, for example, a wire break. An
Danfoss A/S © 2020.02
8.1 Connecting Safe Digital Inputs.
Functions
AN327351953089en-000101 / 130R0578| 17
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