
B-64044EN/01 CONNECTION 1.CONNECTING THE DeviceNet
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- When there are differences in total power consumption between the left side and
the right side (example 3)
The following provides an example of placing the power supply for
communication at a point slightly displaced from the center of a
network using a thick-wire cable (THICK cable) with a total extended
length of 240 m for supplying power.
Power on one side may become insufficient even though the power
supply for communication is placed in the center. This is because
there are differences in total power consumption between the left and
the right. In this case, try to displace the power supply slightly from
the center to satisfy the conditions.
Power consumption for each node is assumed as shown below.
When the power supply is placed in the center
Terminator
Node Node
Power supply
for
communication
erminator
Power tap
NodeNode
120m
Main cable (5-wire cable)
0.85A0.25A
1.25A1.1A
120m
3 m or less
Node
0.5A
Node
0.25A
Total extended length of power supply line (left side) = Total
extended length of power supply line (right side) = 120 m
Total power consumption (left side) = 1.1A+1.25A+0.5A=2.85A
Total power consumption (right side) =0.25A+0.25A+0.85A=
1.35A
Maximum current obtained from the table for thick-wire cables (left
side) = Approx. 2.5 A
Maximum current obtained from the table for thick-wire cables (right
side) = Approx. 2.5A
(These values are obtained by linear approximation between 100 and
l50 m.)
Since "Total power consumption (left side) > Maximum current (left
side)" is satisfied, power on the left side becomes insufficient.
Therefore, move the power supply to the left as shown in the figure
below.
Terminator
Node Node
Power supply for
communication
Terminator
Power tap
NodeNode
140m
Main cable (5-wire cable)
0.85A0.25A
1.25A1.1A
100m
3 m or less
Node
0.5A
Node
0.25A
Total extended length of power supply line (left side) = 100 m
Total extended length of power supply line (right side) = 140 m
Total power consumption (left side) = 1.1A+1.25A=2.35A
Total power consumption (right side) =0.5A+0.25A+0.25A+
0.85A=1.85A
Maximum current obtained from the table for thick-wire cables (left
side) = Approx. 2.93A