Mitsubishi Electric MELCEC Q Series User Manual page 193

11. TROUBLESHOOTING
Table 11.3 Faults with the output circuit and the corrective actions (continued)
Situation
When the
external power
Example supply turns
5 on, the load
turns on for a
moment.
Cause
Erroneous output due to the stray capacitance (C) between
collector and emitter of photocoupler.
There is no erroneous output at normal road.
An erroneous output may occur at high sensitivity load
(such as solid state relay).
Output module, Combined module
Photocoupler
C
Tr1
IC
Constant
voltage circuit
If the external power supply is turned on precipitously, Ic
current flows due to the stray capacitance (C) between
collector and emitter of photocoupler.
Ic current flows to the next stage of transistor Tr1 gate and Y0
output turns on by 100 s
SW: External power
supply (24V) at On
Output Y0
Y0
CTL+
SW
COM-
24V
10ms or less
Approx. 100 s
11 - 26
Countermeasure
When turning on or off the external power,
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 Secondary
side side
external power supply
Programmable
SW1
controller
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.
Y0
R1
CTL+
C1
COM-
24V
R1: Several tens of ohms
Power capacity
(external power supply current*
resistance value (3 to 5)*
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 40
-6
=12 10 -3 s
=12ms
SW
)
1 2
2