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11 TROUBLESHOOTING
11.5 Examples of Troubles with the I/O Module
Troubleshooting for output circuit
This section describes the troubleshooting for output circuit.
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.)
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 100s.
Y0
C
SW
24V
Ic
Tr1
COM-
CTL+
Output module
Photocoupler
Constant-
voltage circuit
Load
SW: External power
supply (24V)
at On
10ms or less
Output Y0
Approx.100µs
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