Omron DEVICENET -, Operation Manual

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95
Step 1: Evaluating the Configuration with Graphs Section 3-4
nected in the very center of the Network. Placing it slightly off center allows
power to be supplied properly to all nodes.
The current consumption for individual nodes is as follows:
Total power supply length on left = Total power supply length on right = 120 m
Total current consumption on left: 1.1 + 1.25 + 0.5 = 2.85 A
Total current consumption on right: 0.25 + 0.25 + 0.85 = 1.35 A
Maximum current on the left side (see table for thick cable) = approx. 2.5 A
Maximum current on the left side (see table for thick cable) = approx. 2.5 A
(using straight line approximation between 100 to 150 m)
Because the total current flow on the left side (2.85 A) is greater than the max-
imum current allowed on the left side (2.56 A), the power supply cannot sup-
ply current to all nodes properly when it is placed at the center of the network.
This problem can be corrected by moving the communications power supply
as shown in the following diagram.
Total power supply length on left = 100 m
Total power supply length on right = 140 m
Total current consumption on left: 1.1 + 1.25 = 2.35 A
Total current consumption on right: 0.5 + 0.25 + 0.25 + 0.85 = 1.85 A
Maximum current for 100 m on the left (see table for thick cable) = 2.93 A
Maximum current for 140 m on the right (see table for thick cable) = 2.1 A
(using straight line approximation between 100 to 150 m)
Because the total current flow on both the left and right sides is now less than
the allowed maximum current, the power supply can be placed as shown in
the diagram and supply current properly to all nodes.
120 m 120 m
3 m
max.
1.25 A 0.5 A 0.25 A 0.25 A 0.85 A 1.1 A
Power Supply Tap
Power
Supply
Node Node Node
Terminating
Resistor
Node Node Node
Terminating
Resistor
Trunk line
Power supply cable
Trunk line
(5-wire cable)
Trunk line
(5-wire cable)
100 m 140 m
3 m
max.
1.25 A 0.5 A 0.25 A 0.25 A 0.85 A 1.1 A
Power Supply Tap
Power
Supply
Node Node Node
Terminating
Resistor
Node Node Node
Terminating
Resistor
Trunk line
Power supply cable
Trunk line
(5-wire cable)
Trunk line
(5-wire cable)