Omron DEVICENET Operation Manual page 115

Step 1: Evaluating the Configuration with Graphs
Example 1:
Power Supply at the
End of the Network
Power Supply Tap
Terminating
Resistor
Power
Supply
Example 2:
Power Supply in the
Center of the Network
Terminating
Node
Resistor
0.1 A
Example 3:
Uneven Power Supply
Distribution
94
In this example, the power supply is at one end of a Network with a total
length of 200 m of thick cable. The power supply is located on the end of the
Network. The current consumption of the individual nodes is as follows:
Node Node
0.1 A 0.15 A
200 m
Total power supply length = 200 m
Total current consumption = 0.1 + 0.15 + 0.05 + 0.25 + 0.1 = 0.65 A
Maximum current for 200 m (see table for thick cable) = 1.53 A
Because the total current consumption (0.65 A) is less than the maximum cur-
rent (1.53 A), the power supply can be placed at the end of the network and
supply current to all nodes.
In this example, the power supply is in the center of a Network with a total
length of 240 m of thick cable. Because the power supply is in the center, the
maximum permissible current can flow both to the left and right, so the power
supply can supply twice as much current as it could when placed at the end of
the network. The current consumption for individual nodes is as follows:
Power Supply Tap
Trunk line
(5-wire cable)
Node Node
0.25 A 0.2 A
120 m
Total power supply length on left = Total power supply length on right = 120 m
Total current consumption on left: 0.1 + 0.25 + 0.2 = 0.55 A
Total current consumption on right: 0.15 + 0.25 + 0.15 = 0.55 A
Maximum current on the left side (see table for thick cable) = approx. 2.5 A
Maximum current on the right side (see table for thick cable) = approx. 2.5 A
(using linear approximation between 100 to 150 m)
Because the total current flow (0.55 A) is less than the maximum current
(approx. 2.5 A) on both the left and the right sides, the power supply can be
placed at the center of the network and provide power to all nodes.
In this example, the power supply is initially located in the center of a Network
with a total length of 240 m of thick cable. The power supply is moved to one
side because the current consumption is significantly higher on that side and
the current flow to that side would be insufficient if the power supply were con-
Node Node
0.05 A 0.25 A
Trunk line
(5-wire cable)
Node
0.15 A
3 m
max.
Power
Supply
120 m
Section 3-4
Terminating
Node
Resistor
0.1 A
Trunk line
Power supply cable
Terminating
Node Node
Resistor
0.25 A 0.15 A
Trunk line
Power supply cable