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MELSEC-Q

12 CONTROL SUB FUNCTIONS

12.4.4 Hardware stroke limit function

WARNING

When the hardware stroke limit is required to be wired, ensure to wire it in the negative logic using b-contact.
If it is set in positive logic using a-contact, a serious accident may occur.

In the "hardware stroke limit function", limit switches are set at the upper/lower limit of
the physical moveable range, and the control is stopped (by deceleration stop) by the
input of a signal from the limit switch. Damage to the machine can be prevented by
stopping the control before the upper/lower limit of the physical moveable range is
reached.
Hardware stroke limit switches are normally "installed inside the stroke limit/stroke end
on the drive unit side", and the control is stopped before the stroke limit/stoke end on
the drive unit side is reached.

The details shown below explain about the "hardware stroke limit function".
[1] Control details
    [2] Wiring the hardware stroke limit
[3] Control Precautions
    [4] When the hardware stroke limit is not used

[1] Control details

The following drawing shows the operation of the hardware stroke limit function.

Mechanical stopper

QD75

Movement
direction

QD75 control moveable range

Start

Drive unit
stroke limit

Lower limit

Upper limit

Deceleration stop at
upper limit switch
detection

Deceleration stop at
lower limit switch
detection

Lower limit switch

Upper limit switch

Drive unit
stroke limit

Drive unit

Fig. 12.22 Hardware stroke limit function operation