42
Network Configuration Section 2-2
Configuration A:
Configuration B:
Note The low voltage limit for the internal circuit power supply is higher than the low
voltage limit for the communications power supply. To meet the voltage speci-
fications for the internal circuit power supply, be sure to follow the specifica-
tions listed in SECTION 3 Communications Power Supply Methods.
2-2-10 Grounding Methods
Proper Grounding
Practices
Ground the DeviceNet shield wire to 100 Ω max. at one and only one point in
the network. Grounding more than one point can cause ground loops and
noise in the network.
Generally, the communications power supply’s FG terminal is grounded to
100
Ω max. and connected to the V- terminal and the Power Supply Tap’s
shield (S) terminal, as shown in example A below. It is also acceptable to con-
nect the communications power supply’s FG terminal and the V- terminal and
ground the network from the Power Supply Tap’s shield (S) terminal, as shown
in example B below.
In either case, ground the network as close to the center of the network as
possible.
When there are two or more communications power supplies in the network,
determine which power supply is closest to the center of the network. Connect
V− V+ − +
24 VDC
24 VDC
V− V+ − +
Shared communications
and internal circuit
power supply
Correct
Communications
power supply
Internal circuit
power supply
Communications
power supply
Internal circuit
power supply
Vv V+ − +
24 VDC
V− V+ − +
24 VDC
Incorrect
Shared communications
and internal circuit
power supply
Communications
power supply
Internal circuit
power supply
Communications
power supply
Internal circuit
power supply
V+
CAN H
CAN L
V−
V+
V+ V− S
V+ V− FG
CAN H
CAN L
V−
V+
CAN H
CAN L
V−
V+
V+ V− S
V+ V− FG
CAN H
CAN L
V−
Power Supply Tap
Example A Example B
Power Supply Tap
Shield (S) Shield (S)
DeviceNet
cable
Communications
power supply
Ground to
100
Ω max.
Ground to
100
Ω max.
Shield (S) Shield (S)
DeviceNet
cable
Communications
power supply
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