External Wiring Precautions - Mitsubishi Electric MELSEQ FX3S Series User Manual

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

12.2.3 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.
2. Contact protection circuit for inductive loads
When an inductive load is connected, connect a diode
(for commutation) in parallel with the load as necessary.
The diode must comply with the following specifications.
Item
Reverse voltage 5 to 10 times of the load voltage
Forward current Load current or more
3. 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.
12.2 External Wiring of Transistor Output (Sink/Source) Type
Guide
12 Output Wiring Procedures
Load
Fuse
Load
Fuse
Inductive
load
Fuse
Inductive
load
Fuse
Sink output type
+
Limit of
normal rotation Interlock
Limit of
reverse rotation
Source output type
–
Limit of
normal rotation Interlock
Limit of
reverse rotation
11
Sink output type
12
Y000
COM0
Main unit
13
Source output type
Y000
+V0
14
Main unit
Sink output type
Y000
15
COM0
Main unit
Source output type
16
Y000
+V0
Main unit
17
–
Normal
rotation
Reverse A
rotation
PLC output
element
+
Normal
rotation
B
Reverse
rotation
PLC output
element
C
115