Omron DEVICENET -, Operation Manual

Page: 105 / 163

84
Minimizing Noise in the Network Section 2-5
Considerations when
Using Flat Cable To prevent unstable operation due to interference when using flat cable in mul-
tiple DeviceNet systems, keep each flat cable at least 5 mm apart from any
other flat cable.
2-5-2 Correcting Malfunctions due to Noise
When noise is thought to be the cause of a malfunction in the DeviceNet net-
work, the following countermeasures may be effective.
Problems with the
Communications
Cable Shielding
Isolate the communications cable shielding wire by disconnecting it from the
ground.
Disconnecting the ground will reduce the noise transferred from the ground to
the communications cable. This countermeasure also reduces the noise cur-
rent that flows in the shield wire.
Problems with the
Communications
Power Supply
Isolate the communications power supply.
This countermeasure reduces the noise transferred from the communications
power supply ground to the communications cable and the noise current that
flows in the communications cable. A switching power supply is usually con-
nected to the case with capacitors as shown below, so the power supply itself
must be insulated from the control board as well as being disconnected from
the FG terminal.
Typical Switching Power Supply Construction
Isolating the Communications Power Supply
AC power supply AC input
Switching power supply
Power
supply
circuit
DC output
Case
Typical switching power supply construction
S82J Power Supply
S82Y- @@ N (Mounting Tool)
DC power supply
Example 1:
Isolating an S82J Power Supply
Example 2:
Isolating another Power Supply
Insulator such as
plastic or acrylic