Troubleshooting For Output Circuit - Mitsubishi Electric NZ2GF2B1-16D User Manual

12.6.2

Troubleshooting for output circuit

This section describes the troubleshooting for output circuit.
(1) A load momentarily turns on when the external power supply is powered on
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
Photocoupler
C
Ic
Constant-
voltage circuit
When the external power supply is powered on rapidly, the current (Ic) flows
due to the stray capacitance(C).
The current (Ic) flows to the gate of the transistor (Tr1) of the next stage and
the output Y0 turns on for approximately 100s.
SW: External power
supply (24V)
at ON
Output Y0
*1 For the current consumption of the external power supply for output part, refer to the manuals.
*2 Select the power capacity of resistor to be 3 to 5 times as large as the actual power consumption.
252
Cause
Tr1
Y0
CTL+
SW
COM-
24V
10ms or less
Approx.100 s
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.
When installing the switch to the secondary side, connect a capacitor and
resistor, and increase the rise time (10ms or more).
• Sink output
Load
• Source output
R1: Several tens of ohms
Power capacity &Operator_GreaterEqual; (external power supply current
resistance value  (3 to 5)
C1: Several hundreds of microfarads 50V
(Example)
R1 = 40, C1 = 300F
Time constant is calculated as shown below.
C1  R1 = 300  10
-3
= 12  10
s
= 12ms
Action
Primary Secondary
side side
External power
supply
SW1 Programmable
controller
Y0
R1
CTL+
C1
COM-
24V
Y0
R1
CTL-
C1
COM+
24 V
*2
- 6
 40
Load
SW
Load
SW
*1 2

)