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Programmable Logic Controllers
2.5
Controller Design
All the controllers in the series have the same basic design. The main functional elements and
assemblies are described in the glossary in section 2.5.7.
2.5.1
Input and output circuits
The input circuits use floating inputs. They are electrically isolated from the other circuits of
the PLC with optical couplers. The output circuits use either relay or transistor output techno-
logy. The transistor outputs are also electrically isolated from the other PLC circuits with optical
couplers.
The switching voltage at all the digital inputs must have a certain value (e.g. 24 V DC). This volt-
age can be taken from the PLC's integrated power supply unit. If the switching voltage at the
inputs is less than the rated value (e.g. <24 V DC) then the input will not be processed.
The maximum output currents are 2 A on 250 V three-phase AC and non-reactive loads with
relay outputs and 0.5 A on 24 V DC and non-reactive loads.
2.5.2
Layout of the MELSEC FX
Mounting hole
Power supply
connection
Interface for expansion
adapter boards
Cutout for adapters or
control panel
2 analog potentiometers
Connection for
programming units
Connection for the
service power supply
Terminals for
digital outputs
FX Beginners Manual
base units
1S
0 1 2 3
4 5 6 7
IN
POW ER
RUN
ERRO R
FX -14M R
1S
OUT
0 1 2 3
4 5
M IT SU BI SH I
Controller Design
Protective cover
Terminal cover
Terminals for
digital inputs
LEDs for indicating
the input status
RUN/STOP switch
LEDs for indicating
the operating status
LEDs for indicating
the output status
Protective cover
2 – 7
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