Technology instructions
10.3 Motion control
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
725
Table 10- 51 Configuration parameters for homing the axis
Input reference point switch
(Active and passive homing)
Select the digital input for the reference point switch from the drop-down list box. The
input must be interrupt-capable. The onboard CPU inputs and inputs of an inserted
signal board can be selected as inputs for the reference point switch.
The default filter time for the digital inputs is 6.4 ms. When the digital inputs are used
as a reference point switch, this can result in undesired decelerations and thus inac-
curacies. Depending on the homing velocity and extent of the reference point switch,
the reference point may not be detected. The filter time can be set under "Input filter"
in the device configuration of the digital inputs.
The specified filter time must be less than the duration of the input signal at the refer-
Reference point switch
(Active and passive homing)
• Active homing: Select whether the axis is to be referenced on the bottom or top
side of the reference point switch. Depending on the start position of the axis and
the configuration of the homing parameters, the reference point approach se-
quence can differ from the diagram in the configuration window.
• Passive homing: With passive homing, the traversing motions for purposes of
homing must be implemented by the user via motion commands. The side of the
reference point switch on which homing occurs depends on the following factors:
– "Reference point switch" configuration
– Current travel direction during passive homing
Auto reverse after reaching the
hardware limit switches
(Active homing only)
Activate the check box to use the hardware limit switch as a reversing cam for the
reference point approach. The hardware limit switches must be configured and acti-
vated for direction reversal.
If the hardware limit switch is reached during active homing, the axis brakes at the
configured deceleration (not with the emergency deceleration) and reverses direction.
The reference point switch is then sensed in reverse direction.
If the direction reversal is not active and the axis reaches the hardware limit switch
during active homing, the reference point approach is aborted with an error and the
axis is braked at the emergency deceleration.
Approach direction
(Active and passive homing)
With the direction selection, you determine the "approach direction" used during ac-
tive homing to search for the reference point switch, as well as the homing direction.
The homing direction specifies the travel direction the axis uses to approach the
configured side of the reference point switch to carry out the homing operation.
Approach velocity
(Active homing only)
Specify the velocity at which the reference point switch is to be searched for during
the reference point approach.
Limit values (independent of the selected user unit):
Start/stop velocity ≤ approach velocity ≤ maximum velocity
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