Installation manual

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Opens or shorts may be the biggest problem. On an idle bus (without traffic) voltages can indicate
problems. CAN_L and CAN_H should be about 2.5 to 3.0 volts relative to V-. If there is traffic,
CAN_L will be a little lower, CAN_H a little higher.
Use an OHM meter to check resistance between CAN_H and CAN_L when idle. This should be
about 60 ohms (two 120 ohm terminators in parallel). This value may be as low as 50 ohms if
there are many nodes attached. Make sure all wires are well attached to the right places. The V+
level, relative to V-, should always be between 11 to 25 volts.
One common problem people run across is incorrect setting of baud rates and node addresses.
Always verify the nodes address and baud rate before installing it on a network. And try not to
change a nodes baud rate while on the network. Do all baud changes on a point-to-point only
connection.
Ground Loops
Before trying this make sure the shield is grounded in only one place.
Use the oscilloscope to determine if there are ground loops in your system. You should NOT see
60 Hz or Harmonics in your signal. Assuming you use DC coupling on the oscilloscope you
should see....
2.8 VDC offset on both Can_High & Can_Low NO Sinusoidal signal; ie 60 Hz components.
DeviceNet Cable (Color Codes and Signals)
BLACK Common -- COM
BLUE-- Signal Low -- CAN_L
Uninsulated Shield -- SHIELD
WHITE Signal High -- CAN_H
RED Power Supply -- VDC+
GREEN Chassis Ground -- EARTH GROUND
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