Omron NT-DRT21, Operation Manual

Page: 52 / 135

3-4 Section Grounding the Network
37
Internal Circuitry of the Power Supply Tap
Power Supply Tap
5-wire cables
on side B
Schottky
diode
Fuses used:
Little fuse 312008
Rated amperage: 8 A
Rated voltage: 250 V
6.35
Φ
x 31.75 mm
Ground
terminal
Power supply device
V+
CAN H
Shield
CAN L
V–
V–
Fuse A Fuse B
V+
CAN H
Shield
CAN L
V–
5-wire cables
on side A
V+
Remove fuse A when disconnecting cables on side A, and fuse B when discon-
necting cables on side B.
3-3-7 Dual Power Supply
Power Supply Taps can be used to construct a dual power supply system in the
network. Dual power supply differs from parallel operation of power supplies, so
the following restrictions apply.
Dual power supply is basically used to ensure backup power supply, not parallel
operation of power supplies. Therefore, each power supply to be used must
meet the power allocation specifications (must satisfy steps 1 and 2).
3-4 Grounding the Network
The DeviceNet network is grounded only one point to prevent ground loops.
Also, connect the ground as close as possible to the center of the network.
Connect the cable shield to the ground terminal (FG) on the communications
power supply and then connect to a ground of 100
Ω
max., as shown in the fol-
lowing diagrams.
Power supply with cable grounded
(one location only)
Power supply without cable grounded
T-branch Tap or Power Supply Tap
Communications
power supply
Ground (100
Ω
max.)
Communications
cable
Power Supply Tap
Communications
power supply
Ground (100
Ω
max.)
Communications
cable
V+
CAN H
Shield
CAN L
V– FG
V+
V+ V– FG
CAN H
Shield
CAN L
V+
V– V–
If more than one communications power supply is connected to the same net-
work, ground only the one nearest the center of the network. Do not connect the
shield wire at the other power supplies. Always use Power Supply Taps when
connecting more than one communications power supply to the same network.
(The power supplies are not counted as network nodes.)
Note 1. Always ground the communications cable shield at one and only one loca-
tion in the network.
Restrictions