Omron OMNUC W R88A-NCW152-DRT, Manual

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6 DeviceNet Communications
6.3.1 Providing the Communications Power Supply
6-14
6
Example
The following example shows a Network that requires power to be supplied for 240 m on
thick cable. The power supply is located in the center of the network.
• Calculation on the left of the power supply
Node 1: (120
×
0.015
+
3
×
0.005)
×
0.1
=
0.1815 (V)
Node 2: (80
×
0.015
+
2
×
0.005)
×
0.25
=
0.3025 (V)
Node 3: (40
×
0.015
+
1
×
0.005)
×
0.2
=
0.121 (V)
→
0.1815
+
0.3025
+
0.121
=
0.605 V
≤
4.65 V
Thus, the best location for the nodes can be determined by using the condition formula.
• Calculation on the right of the power supply
Node 4: (40
×
0.015
+
1
×
0.005)
×
0.15
=
0.09075 (V)
Node 5: (80
×
0.015
+
2
×
0.005)
×
0.25
=
0.3025 (V)
Node 6: (120
×
0.015
+
3
×
0.005)
×
0.15
=
0.27225 (V)
→ 0.09075 + 0.3025 + 0.27225 = 0.6655 V ≤ 4.65 V
Thus, the best location for the nodes can be determined by using the condition formula.
„ Step 3: Splitting the System into Multiple Power Supplies
Go to Step 3 if the best location for the nodes cannot be calculated from the formulae. In the
third step, there are multiple power supplies and the power supply system is split.
Splitting the Power Supply System
• Be sure to use a Power Supply Tap for each power supply when the network is supplied
by two or more power supplies.
• Remove the fuses in the Power Supply Tap to split the power supply system.
Once the power supply system is split, return to Step 1 or 2, and determine the best location
of the nodes in each system.
Communications
power supply
Node 1
Trunk line
(DeviceNet special cable)
Terminating
resistor
0.1 A 0.25 A 0.2 A 0.15 A 0.25 A 0.15 A
40 m 40 m 40 m 40 m 40 m 40 m
Within 3 m
Trunk line
(DeviceNet special cable)
Terminating
resistor
Node 2
Node 3 Node 4 Node 5 Node 6