Omron DEVICENET - Minimizing Noise in the Network; Precautions to Prevent Noise

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Minimizing Noise in the Network Section 2-5
2-5 Minimizing Noise in the Network
2-5-1 Precautions to Prevent Noise
• To prevent inductive noise, separate the communications lines, PLC
power supply lines, and other power lines. In particular, be sure to keep
the power lines for inverters, motors, regulators, and contactors at least
300 mm away from both the communications lines and the power supply
lines. Also, provide separate conduits or ducts for the communications
lines and power lines.
• Make the power supply lines to the control panel as short as possible, use
heavy-gauge wire, and ground the power supply properly (100
Ω max.)
• Avoid installing any DeviceNet devices in a control panel that contains
high-voltage devices.
• Install surge suppressors on devices that generate noise, particularly
devices that have an inductive component such as motors, transformers,
solenoids, and magnetic coils.
• If a surge suppressor cannot be installed, installing a ferrite core directly
next to the device's contacts, such as a contactor may be effective.
• Noise emanating from the communications cable can be reduced by
installing a ferrite core on the communications cable within 10 cm of the
DeviceNet Master Unit.
300 mm min.
300 mm min.
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2
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1
2
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2
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PLC power lines and
general control circuit lines
Communications lines
and PLC I/O lines
Power lines
Ground
(100
Ω max.)
Suspended
ducts
Floor
ducts
Conduit
Power lines
Communications lines
and PLC I/O lines
Low-voltage
communications
cables
Control
cables
Power
cables
Surge suppressor
(just before device)
Surge suppressor
(just before device)
Device
(such as a motor)
Device
(such as a motor)
DC Device
AC Device
Ferrite core
Device
(such as a motor)