Siemens SIMATIC NET PC PROFIBUS, Руководство по эксплуатации, Страница: 27 / 36

PROFIBUS Optical Bus Terminal (OBT)
Operating Instructions, 04/2016, C79000-G8976-C122-07
27
Help with problems during operation
6
6.1 Help with problems during operation
LED display Possible cause of problems
L+ 24 V LED not lit
•
Power supply failed
• OBT defective
L+ 24 V LED flashes
• The transmission speed could not be set
CH1 LED not lit
•
One or more wires of the RS-485 bus cable is interrupt-
ed
•
Wires A and B of the RS-485 bus cable had been
swapped over
•
Connected PROFIBUS node is defective or is not trans-
mitting
•
PROFIBUS node or RS-485 segment is not connected
or connected or PROFIBUS node is not turned on
CH1 LED lit
PROFIBUS nodes are, however, signaling problems on the
bus
• Wires A and B of the RS-485 bus cable had been
swapped over
•
Short circuit on the RS-485 bus cable
• Interruption of one of the two wires of the RS-485 bus
cable and A or B connected to wrong terminal
•
Missing or incorrect termination
CH2, CH3 LED not lit
•
Send and receive FO cable connected to wrong socket
•
Interruption of the receive FO cable to the partner mod-
ule
•
No partner module connected or connected partner
module is not turned on
•
Connected partner module is defective (not transmitting)
CH2, CH3 LED lit
PROFIBUS nodes are, however, signaling problems on the
bus
•
FO cable connector is loose (bad contact)
• FO cable link to the neighboring module is too long
•
Interruption of the receive FO cable with extraneous light
entering
If no LED indicates an error and you are still experiencing problems in communication (for
example an acknowledgement is not received, unexpected frames), you should check the
monitoring times set on the PROFIBUS nodes (for example the slot time). You will find
details in the description of your PROFIBUS end devices and your configuration software.