10 TROUBLESHOOTING
10.5 Fault Examples with the Safety Remote I/O Module
131
10
Output circuit troubles and corrective actions
The load in the off state momentarily turns on at power off (transistor output).
■Cause
When an inductive load is connected, the load [2] in the off state may turn on due to a sneak current from the back EMF at the
shutoff [1].
■Action
Take either of the following two actions:
• To suppress the back EMF, connect a diode in parallel with the load under the back EMF influence [3].
• Configure another current path by connecting a diode across positive and negative of the external power supply.
D1 indicates the following.
Reverse voltage VR (VRM)
*1
Forward current IF (IFM)
*2
*1 Approximately 10 times as high as the rated load voltage in the performance specifications
Example: 24VDC Approximately 200VDC
*2 Twice as high as the maximum load current (common) in the performance specifications or more
Example: 2A/1 common 4A or higher
Y0
Y1
IO24V
ON
OFF
COM-
IO24G
[2]
[3]
Load
Load
Back electromotive
force
[1] Shut off
Source output
Load
Back electromotive
force
+
-
ON
OFF
Y0
Y1
COM-
IO24V
IO24G
[2]
[3]
D1
Load
Load
Source output
Back electromotive
force
[1]
Shut off
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