Use ctrlX SAFETY to control STO function of ctrlX DRIVE

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In the following we show to you how to control the STO function of ctrlX DRIVE via ctrlX SAFETY in using digital I/Os.

All the functions and screen shots are based on:

  • ctrlX SAFETY Engineering version >=
  • SAFEX Runtime / Firmwareversion >= (C-sample)
  • ctrlX DRIVE Engineering version 01V12
  • Runtime / Firmware version of drive AXS-V0304
  • Runtime / Firmware version of drive AXS-V0210

A connection to the ctrlX SAFETY control and ctrlX DRIVE has been successfully established, the devices are correctly wired and 24 V are successfully put on. As well the engineering tools ctrlX SAFETY and ctrlX DRIVE Engineering have been started.


Mind that attached to the article you find the ctrlX SAFETY program and ctrlX DRIVE parameter as sample. The word file of the article is as well attached for download for use without Internet connection.


1. Function of the established SAFEX logic program

The principle function of the SAFEX logic program is the following:


If at the ctrlX SAFETY the EMERGENCY STOP button is pressed or the ModeSelector is switched, the non-safety-functional E-Stop function at the drive is activated immediately, which leads to a deceleration of a still moving axis. With a time delay of in here chosen 0,5 s, which is the time the axis needs to stop in worst case, the SAFEX control activates the safe STO function at the drive which prohibits a further movement. If the drive acknowledges the standstill (which is a non-safety-function only) already before the 0,5 s are exceeded, the safe STO function is directly activated after the drive acknowledges this standstill condition.

If the EMERGENCY STOP button is released again, the Reset button needs to be shortly pressed that the EMERGENCY STOP and thus the STO function is released again as well. Then the drive can be activated again.

If only the ModeSelector has been switched and is now switched back again, the STO function is directly released again. No Reset button needs to be pressed. Then the drive can be activated again.

Timing diagrams

The following timing diagram show the sequence for the functionality:


Fig. 1.: Timing diagram with normal behavior at pressing EMERGENCY STOP button (axis is in movement but reaches standstill more quickly than time foreseen)


Fig. 2.: Timing diagram with behavior at pressing EMERGENCY STOP button (axis is in movement but doesn´t reach standstill in the time foreseen)

The timing diagram for switching the ModeSelect is exactly the same like for pressing the EMERGENCY STOP button.



Fig. 3.: Timing diagram after releasing EMERGENCY STOP button


Fig. 4.: Timing diagram after switching ModeSelect back

2. Wiring schematics

The SAFEX control´s input devices are:

  • One double channel EMERGENCY STOP button fed by pulsed 24V
  • One double channel Mode Select switch fed by pulsed 24V
  • One single channel reset button fed by non-pulsed 24V
  • Two single channel inputs coming from two ctrlX DRIVE indicating that standstill is achieved

The output devices are:

  • One single channel output for control of so-called E-Stop function of drives (quick changeover to standstill)
  • Two OSSD fed outputs connected to double channel STO input of drives


Fig. 5.: Wiring schematics

3. Settings inside SAFEX control

The settings of the SAFEX control and the devices connected to the ctrlX SAFETY control should be according to the following.


Fig. 6.: Settings of SAFEX control


Fig. 7.: Settings of “Emergency Stop” button connected to SAFEX control


Fig. 8.: Settings of “ModeSelect” switch connected to SAFEX control


Fig. 9.: Settings of “Start/Reset” button connected to SAFEX control



Fig. 10.: Settings of “Drive standstill” inputs connected to SAFEX control


Fig. 11.: Settings of E-Stop output of SAFEX control

Mind that the E-Stop is not using an OSSD output.
In order to achieve this, the property SIL Level of the SAFEY control needs to be set to SIL2 (see Fig. 6). Then the Output type may be selected as Standard (see in here Fig. 11)”.
If using OSSD output signals the overall SIL Level for those safety functions is SIL3, even if only SIL2 is been selected.









Fig. 12.: Settings of STO outputs of SAFEX control

4. Safe logic inside SAFEX control

The safe logic inside the SAFEX control is created according to the following schematics.


Fig. 13.: Safe logic inside SAFEX control


Fig. 14.: Settings of Restart block


Fig. 15.: Settings of Timer (in here as delay time 0,5 s is chosen, in your application this time may differ)

5. Wiring of ctrlX DRIVE

The wiring of ctrlX DRIVE with STO is done according to the following:


Fig. 16.: Wiring of ctrlX DRIVE with STO

6. Settings of ctrlX DRIVE

The settings inside ctrlX DRIVE are done according to the following:


Fig. 17.: Settings of ctrlX DRIVE (1): I/O signal settings


Fig. 18.: Settings of ctrlX DRIVE (2): Error reaction settings


Fig. 19.: Settings of ctrlX DRIVE (3): E-Stop reaction settings


Record of revision: Version 03, 2021-09

Editorial Department: Drives Support [UwWe]



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