Omron OMNUC W R88A-NCW152-DRT, Руководство пользователя

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6 DeviceNet Communications
6.3.1 Providing the Communications Power Supply
6-6
6
6.3 Precautions for Communications Line Design
This section explains how to provide communications power supply and communications line
noise prevention.
6.3.1 Providing the Communications Power Supply
This section explains how to locate the communications power supply and its concept, how
to determine the located power supply (steps 1 to 3) , and dual power supply.
„ Locating the Communications Power Supply and Its Concept
The power supply location patterns and the basic concept are described below.
Basic Concept
Basic precautions are as follows:
• The communications power supply must be 24 V DC.
• Make sure that the power is supplied from the trunk line.
• When providing power to several nodes from one power supply, try to locate the nodes
in both directions from the power supply if possible.
• Provide power through Power Supply Taps. It is, however, possible to use T-branch Taps
instead when there is one communications power supply in the system and the total cur-
rent consumption is 5 A or less.
• The power supply capacity for cables is restricted to 8 A for thick cables and 3 A for thin
cables.
• A single network is usually supplied by one power supply. It is, however, possible to
have more than one power supply when power supply specifications cannot be met with
a single power supply. (Refer to
Step 3: Splitting the System into Multiple Power Sup-
plies on page 6-14. )
• Fully consider the power supply capacity allowance in the design.
• If the power supply is switched OFF during the operation of the network, there may be a
malfunction in the nodes.
• The current capacity of the drop line varies according to its length. The longer the drop
line, the lower its maximum capacity becomes. This is the same whether the cable is
thick or thin. Calculate the current capacity passing through the drop line I (the total cur-
rent consumption at the drop line) using the following formula.
• I = 4.57/L
I: Permissible current (A), L: Length of the drop line (m)