When Choosing A Power Supply, Keep The Following Tips; Verify Network Voltages - Parker H Series Installation & Service Instructions Manual

5-8 Correct and Prevent Network Problems
if voltage
on the black V- wire differs from one point
of the network to another by more than
4.65V
between the red V+ wire and the black V-
wire drops below 15V

Verify Network Voltages

Publication DNET-UM072C-EN-P - July 2004
When choosing a power supply, keep the following tips in mind:
We recommend that the DeviceNet power supply be used
IMPORTANT
to power only the DeviceNet network.
• The thin wire trunk line is rated to 3A current flow. The thick wire trunk
line is rated to 8A current flow. In North America, however, current is
limited to 4A. You can install multiple power supplies on a DeviceNet
network, but no section of cable should allow more current flow than
that for which the trunk line is rated.
• If you install multiple power supplies on the network, break the red V+
wire between the power supplies to isolate one power supply from the
other.
• On DeviceNet networks with multiple devices or extra long trunk lines,
which result in drawing large currents at longer distances, common
mode voltage can affect network operation.
then
communications problems could result
The DeviceNet network communicates using a three-wire signal voltage
differential among the CAN_H (white), CAN_L (blue), and V- (black) wires.
DeviceNet messages consists of ones and zeros. A one is recessive, meaning
that the difference in voltage between CAN_H and CAN_L should be as close
to 0V as possible. A zero is dominant, meaning that the difference in voltage
between CAN_H and CAN_L must be within certain limits when the zero bit
is set.
Out-of-range differential voltages can be caused by such factors as:
• opens or shorts in signal wires
• faulty devices (particularly transceivers)
• severe interference
• incorrect media
To check for proper voltage, use a voltmeter in dc mode. Measure voltages at
the DeviceNet scanner.
so you should
• move an existing power supply
closer to the heavier current loads
• add an additional power supply