
1.CONNECTING THE DeviceNet CONNECTION B-64044EN/01
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Maximum current obtained from the table for thick-wire cables (right
side) = Approx. 2.1A
(On the right side, these values are obtained by liner approximation
between 100 m and 150 m.)
This satisfies "Total power consumption < Maximum current" on
both ends and power can be supplied to all nodes.
1.7.4 Verification Using the Expression
When rough calculation by the graph cannot be satisfied, make a
verification based on the actual layout of nodes and the power supply
for communication.
In DeviceNet, the maximum voltage drop allowed in the system is
defined as 5 V for each of the voltage lines (V+ and V-) according to
the voltage specifications of the power supply for communication (24
VDC) and the input voltage specifications of power supplies for
communication for devices (11 to 25 VDC).
Of 5 V, the voltage drop allowed for the main line is 4.65 V and that
allowed for branch lines is 0.35 V.
A voltage drop by a cable is considered as follows.
In the DeviceNet standard, a voltage drop by a cable is defined as 5 V
or less including a margin according to the specifications of the power
supply for communication (24 VDC) and the specifications of power
supplies for communication for devices (11 to 25 VDC).
V1
V2
Voltage drop VA of V+
Voltage drop VB of V-
Voltage supplied to power
supply for communication
Voltage supplied to each node
Vl: Voltage supplied to power supply for communication. V1 is
23V with the fluctuation range of the power voltage considered.
V2: Voltage supplied to each node. V2 must be greater than or
equal to 13 V with a margin considered.
VA: Voltage drop by the power cable (V+)
VB: Voltage drop by the power cable (V-)
In DeviceNet, VA and VB must be less than or equal to 5 V.
The voltage drop by communication cables is defined as 5 V or less
for each of power lines (V+ and V-).
Of 5 V, the voltage drop allowed for main lines is 4.65 V and that
allowed for branch lines is 0.35V.
Expression
First, measure the distances between the power supply and the nodes
and the current consumption of communication units of the nodes.
Check whether the following expression is satisfied. If it is satisfied,
the conditions for supplying power for each node are satisfied.
However, be careful not to exceed the maximum current capacity of a
cable (8 A for thick-wire cables or 3 A for thin-wire cables).