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8. SPECIFICATIONS AND WIRING OF THE I/O BLOCKS
Main or extension module
AC/DC
converter
24+
5
24
24-
V
V 0
Extension block
(d) External circuit for sensor
The input current of this PLC is supplied from the 24VDC power supply in the
PLC. Therefore, when the sensor such as a photoelectric switch is driven by
an external power supply, the voltage of this external power supply should be
24V±4VDC and the output transistor of the sensor should be the NPN open
collector type. However, when the output transistor has sufficient voltage
resistance and there are no diode and resistor in the sensor as indicated in
the dotted line (open collector), the external power supply voltage may be
different.
24VDC
(2) Input connection example
L
N
24+
COM
X000
X001
X002
Input
terminals
24+
4.3kW
X
0
X
1
X
2
X
3
Input
terminals
PLC
24+
IN
4.3k
COM
100 to 240VAC
+10% -15%
Protective ground
conductor with class D
(class-3)
3-wire type
Proximity switch,
photoelectric switch, etc.
2-wire type
8 - 4
MELSEC-A
Sensor
Sneak
External power supply
24±4VDC
Output
transistor
Handle the "power supply circuit",
"empty terminal", "24V+ terminal"
and "COM terminal" correctly in
accordance with Section 2.2
"Performance of the Power Supply Section".
Service power supply for sensor
A bleeder resistor may be needed
for input equipment having a parallel
resistor or for a 2-wire type proximity
switch.
Refer to (3) "Selection of DC input
equipment".
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