Mitsubishi MELSEC System Q Manual page 107

An Introduction to Programming
b Close gate automatically after 20 seconds
When the gate is open limit switch S3 activates and input X3 is switched off. (For safety reasons
S3 is a break contact.) When this happens timer T0 starts the 20s delay (K200 = 200 x 0.1s =
20s). When the timer reaches 20s the gate is closed.
NOTE Timer are described in detail in the next chapter.
b Stop gate with STOP switch
Pressing the STOP button resets the two local variables, stopping the gate motor.
b Identifying obstacles with the photoelectric barrier
If an obstacle is registered by the photoelectric barrier while the gate is closing the close oper-
ation is halted and the gate is opened again.
b Switching the motor off with the limit switches
When the gate is open limit switch S3 is activated and input X3 is switched off. This resets the
local variable OPEN_GATE and stops the motor.
When the gate is fully closed S6 is activated, turning off the motor also. For safety reasons the
limit switches are break contacts. This ensures that the motor is also switched off automatically
(or cannot be switched on) if the connection between the switch and the input is interrupted.
NOTE The limit switches must be wired so that they also switch off the motor automatically without
support from the PLC (see wiring diagram in chapter 4.9.3).
MELSEC System Q Beginners Manual
Programming PLC Applications
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