12
TROUBLESHOOTING
12.5 I/O Module Troubleshooting
12.5.2 Output Circuit Troubleshooting
12 - 259
9
EMC AND LOW
VOLTAGE
DIRECTIVES
10
LOADING AND
INSTALLATION
11
MAINTENANCE AND
INSPECTION
12
TROUBLESHOOTING APPENDICES INDEX
12.5.2 Output Circuit Troubleshooting
This section explains trouble examples and troubleshooting methods in the output circuit.
Table12.20 Output circuit troubleshooting
Condition Cause Corrective Action
Example 1
Excessive
voltage is
applied to load
when output
turns off.
• When load is half-wave rectified inside (This
is typical of some solenoids.)
• When the polarity of the power supply is [1],
the capacitor C is charged. When the polarity
is [2], the voltage charged in C plus the power
supply voltage is applied to across D1. The
maximum value of the voltage is approx. 2.2E.
(This usage does not pose problems to the
output components but may deteriorate the
diode built in the load, causing burnout, etc.)
• Connect a resistor of several ten K to
several hundred K across the load.
Example 2
Load does not
turn off.(Triac
output)
• Leakage current due to the built-in surge
suppressor
• Connect a resistor across the load.
(If the wiring from the output module to the
load is long, be careful since there may be a
leakage current due to the line capacity.)
Example 3
The load is not
turned OFF.
(Triac output)
• The load current is lower than the minimum
load current.
• When the load current is lower than the
minimum load current of the output module,
the triac does not operate since the load
current flows into a phototriac as shown
below.When an inductive load is connected,
the load may not be turned OFF since surge
at the time of OFF is applied to the phototriac.
• Connect a resistor to both ends of a load so
that the load current is higher than the
minimum load current.
Output module
QY22
D1
[1]
[2]
Load
Resistor
Load
Load
Leakage current
QY22
Output module
Resistor
Load
Phototriac
QY22
Triac
Surge suppressor
Control
circuit
Load
Resistor
Load
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