2.5.3.10 The Polarity Of The Hardware Limit Switches - Siemens SIMATIC S5 Manual

Machine Data and their Structure
Fig, 2/1 3 Backlash
The backlash can be a value between O and 64,999 mm (0,1 inches or degrees).
The backlash can only be taken into account when the carriage can be moved directly by the
drive, This is always the case when a distance greater than the backlash has been travel led. In a
reference point approach this is always fulfilled, (=> Section 4.2.3,1 "Reference Point Ap-
proach"). After "setting" the reference point you must make sure that this movement takes place
(to take up any play),
The backlash compensation value is ignored until a distance is travelled which is equal to or
greater than the selected backlash compensation value. Correct detection or display of the ac-
tual position is not affected.
A backlash less than the positioning resolution cannot be compensated. The backlash compen-
sation value is always a multiple of the resolution.

2.5.3.10 The Polarity of the Hardware Limit Switches

In addition to the software limit switches, two hardware limit switches are also evaluated via digi-
tal inputs, These should normally be after the software limit switches. If they are in front of the
software limit switches, they limit the traversing range instead of the software limit switches,
These hardware limit switches can either both be stipulated as normally closed ("1") or both as
normally open ("O") using the parameter "polarity HW limit switches". A normally open switch
generates a positive edge at the corresponding digital input and is therefore high-active, A nor-
mally closed switch generates a negative edge and is therefore low-active. For safety reasons,
you should use normally closed switches as the hardware limit switches. The IP247 then recog-
nizes a wire break during operation as the tripping of a limit switch and stops the movement. The
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Backlash
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M : Motor
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