Mitsubishi Electric MELSEC iQ-R Series User Manual page 127

A load momentarily turns on when the external power supply is powered on.
Cause An incorrect output occurs due to the stray capacitance (C) between collector and emitter of a photocoupler.
When a high sensitivity load (such as solid state relay) is used, this incorrect output may occur.
Output module
C
When the voltage rise time is t1: less than 10ms at the power-on of the external power supply (24VDC) after the switch-on, the stray
capacitance (C) between collector and emitter of the photocoupler allows the current, Ic, to flow into the gate of the transistor Tr1 on the
next stage. As a result, the output Y0 is turned on for about t2: 100s.
Action Action 1: Before turning on or off the external power supply, check that the rise time of the external power supply is 10ms or more. Then,
install a switch (SW1) to the primary side of the external power supply.
Primary side
SW1
Action 2: If installing the switch to the secondary side is required, connect a capacitor and resistor to slow down the rise time (10ms or
more).
However, action 2 is not effective for the following source output modules because of the characteristics of the external power supply
circuit, so that take action 1 above.
• RY40PT5P
• RY41PT1P
• RY42PT1P
Y0
12/24VDC
COM
R1: Several tens of ohms
Power capacity  (External power supply current
C1: Several hundreds of microfarads 50V
<Example>
For R1 = 40 and C1 = 300F
Time constant = C1  R1 = 300  10
*1 Check the current consumption of the external power supply for modules used.
*2 Select the power capacity of resistance to be 3 to 5 times as large as the actual power consumption.
Tr1
Ic
Y0
12/24VDC
Constant-voltage
COM
circuit
24VDC
Secondary side
External power supply
Programmable
controller
Load
R1
SW
C1
24VDC
*1 2
)
-6
 40 = 12  10
Y0
Load
SW
24VDC
Output module
External power supply terminal
*2
 Resistance value  (3 to 5)
-3
[s] = 12ms
9.3 Output Circuit Troubles and Corrective Actions
t2
t1
9 TROUBLESHOOTING
125
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