Mitsubishi MELSEC Q Series User Manual

5 - 10
5.2 Fail-safe Circuit
5
SETTINGS AND PROCEDURES BEFORE OPERATION
(3) Fail-safe measures against C Controller system failure
Failure of the C Controller module is generally detected by the self-diagnostic
function. However, if an I/O control part is faulty, the failure may not be detected by the
C Controller module.
In such a case, all the I/O may turn ON or OFF depending on the failure, and normal
operation and safety of the control target may not be ensured.
Though Mitsubishi products are manufactured under strict quality control, the C
Controller system may fail for unspecific reasons. To prevent mechanical damage
and/or accidents in that case, please configure a fail-safe circuit outside the C
Controller module.
The following shows a system example and a fail-safe circuit example.
* 1 The output module for fail-safe purpose should be loaded in the last slot of the system. (Y80 to
Y8F in the above system.)
* 2 Create a program so that Y80 alternates between ON and OFF at intervals of 0.5 s.
(Use the QBF_Y_Out_BitEx function to turn Y80 ON/OFF.)
* 3 Y80 repeats turning ON and then OFF at 0.5s intervals.
Use a no-contact output module (transistor in the example shown above).
Figure 5.5 System example
Figure 5.6 Fail-safe circuit example
Extension cable
Y80 to Y8F
No. of slots
Output module for fail-safe *
1
16 points
16 points 16 points 16 points16 points
No. of slots
16 points 16 points 16 points16 points
Input
Output
Output
Empty
Output
Output
Output
Input
Input Inout
Y80
0.5s 0.5s
Y80
Y81
Y8F
24V
0V
C Controller
module
T1 T2
24VDC
MC
MC
T2
T1
On delay timer
Off delay timer
1s
1s
External load
L
L
User program *2
Output module
*3

Mitsubishi MELSEC Q Series Specifications

General

Brand	Mitsubishi
Model	MELSEC Q Series
Category	Controller
Language	English