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When an output terminal is off, the LED connected as a load dimly turns on
■Cause
The load operates by the leakage current when the output module is off.
FPGA module
DC output (sink output)
Y0
COM
■Action
Connect a resistor of 5 to 50k in parallel with the LED load.
A load operates only by turning on the external power supply
■Cause
• The external power supply is connected with its polarity reversed.
Load
Y0
Incorrect
External
power
supply
COM-
Output element
protection diode
• The reversed polarity may allow current to flow via the output element protection diode into the load.
■Action
Connect the external power supply with the correct polarity.
Action
LED
24VDC
power supply
Correct
22 TROUBLE EXAMPLES of DC INPUT/OUTPUT
22.2 Troubles and Countermeasures for DC Output Circuits
22
449
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Table of Contents
Troubleshooting
