External Wiring Precautions - Mitsubishi FX3U SERIES User Manual

FX Series Programmable Controllers
3U
User's Manual - Hardware Edition

12.3.4 External wiring precautions

1. Protection circuit for load short-circuits
A short-circuit at a load connected to an output terminal could cause burnout at the output element or the
PCB. To prevent this, a protection fuse should be inserted at the output.
Use a load power supply capacity that is at least 2 times larger than the total rated fuse capacity.
• External Wiring of Sink Output Type
Load
Fuse
• External Wiring of Source Output Type
Load
Fuse
2. Interlock
For loads such as forward/reverse contactors, etc., where a hazardous condition could result if switched ON
simultaneously, an external interlock should be provided for interlocking the PLC's internal programs, as
shown to the right.
• External Wiring of Sink Output Type
Limit of normal
rotation
Limit of reverse
rotation
• External Wiring of Source Output Type
Limit of normal
rotation
Limit of reverse
rotation
216
Y
COM1
PLC
Y
+V0
PLC
Interlock
PLC output
element
Interlock
PLC output
element
12.3 External Wiring of Transistor Output (Sink/Source) Type
12 Output Wiring Procedures