User`s manual

11 - 6 11 - 6
MELSEC-Q
11 I/O MODULE TROUBLESHOOTING
Table 11.2 Output Circuit Problems and Corrective Actions (Continued)
Condition Cause Corrective Action
Example 4
When the
external power
supply turns
on, the load
turns on for a
moment.
Erroneous output due to the stray capacitance (C) between
collector and emitter of hotocoupler.
There is no erroneous output at normal road.
An erroneous output may occur at high sensitivity load
(such as solid state relay)
12/24VDC
COM
Output module, Combined module
Y0
Tr1
C
SW
24V
Photocoupler
Ic
L
Constant
voltage circuit
(1) If the external power supply is turned on precipitously, Ic
current flows due to the stray capacitance (C) between
collector and emitter of hotocoupler.
(2) Ic current flows to the next stage of transister Tr1 gate and
Y0 output turns on by 100
s
SW: External power
supply (24V) at On
10ms or less
Output Y0
Approx.100 s
(1) When the external power turns ON/OFF,
check that the external power supply rising
edge must be 10ms or more, and switch the
SW1 to the primary side of external power
supply.
Primary side
Secondary
side
PLC
SW1
external power
supply
(2) When switching to the secondary side of the
external power supply is required, the
external power supply rising edge
connected a condenser must be slow, and
measured 10ms or more.
COM
Y0
SW
24V
R1
C1
L
12/24VDC
R1: Several tens of ohms
Power capacity
(external power supply
current
*1
)
2
resistance value
(3 to 5)
*2
C1: several hundreds of microfarads 50V
*1 Refer to consumption current of the external
power supply for modules used in this
manual.
*2 Select the power capacity of resistance to be
3 to 5 times lager than the actual power
consumption.
(Example)
R1=40
, C1=300 F
Use the below expression to calculated a
time constant
C1
R1=300 10
-6
40
=12
10
-3
s
=12ms