Adept EX SmartContoller - Manual (Page 91)

Chapter 7: Adept DeviceNet
Termination of the DeviceNet Network
The DeviceNet network uses the Controller Area Network (CAN) bus as the physical layer.
This requires that the trunk line of your DeviceNet network be terminated with a resistor at
each end. This terminates the signal lines.
The terminating resistor:
l Prevents reflection of communication signals on the network.
l
Connects the two signal conductors.
l Must be sealed if the end node uses a sealed tee.
l Must be open if the end node uses an open-style tap.
When using the open-style terminating resistor, connect a 121 ohm, ¼ W resistor to CAN_H
and CAN_L (between blue and white data-pair wires).
NOTE: A terminating resistor must also be used whenever a short drop line exceeds 6 m (20 ft).
Figure 7-5. Example of a Terminating Resistor Installation on a DeviceNet Bus
Power Supply and the DeviceNet Bus
The DeviceNet network allows distribution of power supplies on the network cable system. Fol-
low these general rules to achieve safe and reliable operation:
l
Use power supplies rated at 24 V.
l Minimize installation problems by using a single power supply with sufficient current
to operate all the attached nodes. This must comply with national and international
safety standards.
l Make sure that each power supply incorporates current-limit protection.
l
Make sure each power supply is temperature compensated.
l
Provide over-current protection for each segment of your DeviceNet cable installation.
NOTE: Adept does not supply the 24 V operating voltage for the DeviceNet bus on the Smart-
Controller or any other Adept component.
Adept SmartController EX User’s Guide, Rev. B
Page 91 of 96