Siemens SIMATIC S5 Manual page 101

IP 266
The IP 266 provides two options for establishing a reference point:
• Approach reference point
• Set reference point
Approach reference point
When you configured the drive, you installed a reference point switch. The
reference point switch must lie in the positioning range between the two
hardware limit switches. This switch is required for the "Approach reference
point" mode.
Note:
Hardware limit switches cannot be used as reference point switch.
Figure 5-13 illustrates the use of the various switches and their layout in a drive
system.
From the instant at which a switch is actuated until the instant at which it is
passed, the drive moves a specific distance. This distance, or path, is represented
as the spatial extent of the switches. This extent is absolutely necessary for the
correct functioning of the system. The drive must be so designed that it can be
decelerated from the maximum speed without passing the switch.
Forward
(actual value increases)
N H S
A A A
N : Emergency limit switches start/end
A/E
H : Hardware limit switches start/end
A/E
S : Software limit switches start/end
A/E
Ref: Reference point switch
Figure 5-13. Drive Starting Positions for a Reference Point Approach
EWA 4NEB 812 6057-02
Machine Data, Modes and Traversing Programs
B
A C
REF
Range of the linear axis
A:
B:
C:
D:
D
S H N
E E E
Possible drive
positions prior to a
reference point
approach
5-29