Minimizing Noise In The Network; Precautions To Prevent Noise - Omron DEVICENET Operation Manual

Minimizing Noise in the Network

2-5

Minimizing Noise in the Network

2-5-1

Precautions to Prevent Noise

82
• 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.
Communications lines
and PLC I/O lines
PLC power lines and
general control circuit lines
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.
DC Device
Surge suppressor
(just before device)
• 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.
Ferrite core
• 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.
Suspended
Low-voltage
ducts
communications
cables
Control
300 mm min.
cables
Power
300 mm min.
cables
Ground
(100 Ω max.)
Device
(such as a motor)
Device
(such as a motor)
Section 2-5
Floor
ducts
1
2
1
2
Communications lines
1
Conduit
and PLC I/O lines
1 2
Power lines
2
AC Device
Surge suppressor
(just before device)
Device
(such as a motor)