Profibus DP Troubleshooting - Kone cranes Rev 1507.pdf

17-Jul-23 1
Profibus DP Troubleshooting ABC.ppt
Profibus DP
Troubleshooting ABC

17-Jul-23 2
Profibus DP Troubleshooting ABC
Contents
• Fault top 5
• Siemens S7-300/400 indicator LEDs
• Sub-D 9-pin connectors
• Multimeter troubleshooting
• Signal level troubleshooting
• Troubleshooting checklist

17-Jul-23 3
Fault top 5
1. Termination (80%)
2. Cabling problems (10%)
3. Configuration faults (5%)
4. Faulty devices (3%)
5. Other faults (2%)

17-Jul-23 4
Siemens S7 indicator LEDs 1/5
Master and slave indicator LEDs:
• Indicator LEDs can tell basic start information for troubleshooting.
• There are usually 3 LEDs (Siemens PLC CPU, ET200M).
• LED “SF” = System Failure.
• LED “BF” = Bus Failure.
ON BF SF FAULT CONDITION
1 0 0 Everything OK
1 1 0 No communication
1
1/0
(blinking)
0 Communication, but not in data exchange
1 1 1 Configuration not OK

17-Jul-23 5
SF
BF
ON
Everything OK:
• Only LED “ON” is lit.
• There are no problems with bus
communication.
• All slaves have correct parameters.
• System ready for operation.
SF=0
BF=0
ON=1

17-Jul-23 6
SF
BF
ON
No communication:
• LEDs “ON” and “BF” are lit.
• There are no valid messages detected
on the bus.
• Possible causes:
– Wiring problems (break, cross-
connection…)
– Master PLC is OFF
SF=0
BF=1
ON=1

17-Jul-23 7
SF
BF
ON
Not in data exchange:
• LED “ON” is lit and “BF” is blinking.
• There is communication on the bus, but
the device is not in data exchange.
– “Nobody is talking to the device”.
• Segment wiring & connections are
probably OK.
– Device is not configured to the master
bus layout.
SF=0
BF=0/1
ON=1

17-Jul-23 8
SF
BF
ON
Configuration not OK:
• LEDs “ON”, “SF” and “BF” are lit.
– System configuration is not correct.
– Local problem (configured bus devices
offline…)
SF=1
BF=1
ON=1

17-Jul-23 9
Sub-D 9-pin connectors 1/2
• Usually two bus cables can be
connected into a sub-D connector:
– IN
– OUT
• When termination is switched ON line
OUT is disconnected.
– All devices in the bus after the
termination will be cut out of the active
bus.
OFF ON
OFF ON
T

17-Jul-23 10
Sub-D 9-pin connectors 2/2
• Table underneath shows sub-D connector pins:
PIN SIGNAL DESCRIPTION
1 SHD Shield/functional ground
2 M24 Ground for +24 V output voltage
3 LINE B Bus line B
4 CNTR-P Repeater control signal
5 DGND Digital/data ground
6 VP 5 V supply voltage
7 P24 24 V Output voltage
8 LINE A Bus line A
9 CNTR-N Repeater control signal
PIN 5/DGND
PIN 6/VP
390 Ω
PIN 3/LINE B
PIN 8/LINE A
220 Ω
390 Ω

17-Jul-23 11
Multimeter troubleshooting 1/7
• The resistance (measured with a multimeter) of each device connected in
parallel between the bus lines should be 30kΩ…220kΩ.
• Terminating resistors from both ends of the bus segment should be
disconnected before measurements.
• Before measuring draw a clear picture of the bus wiring and devices:
(T) T
LINE B
LINE A
220Ω
30kΩ…220kΩ
(each device)
220Ω
SHIELD
D
2
C
D
2
H
P
L
C
T T

17-Jul-23 12
Terminating resistor check:
• Measure resistance between lines A
and B. Value should be some kilo-Ohms
(kΩ).
• If there are extra terminating resistors
the measured value will be less than
220 Ω (e.g. 1:215 Ω, 2:100 Ω, 3:70
Ω,…)
D
2
C
D
2
H
P
L
C
Rmeas=Rwires+RD2C||RD2H ||RPLC
11k
Ω
SHD
B
A

17-Jul-23 13
Wires cross-connected:
• Measured resistance between lines A
and B should be some kilo-Ohms
(normally OK value  needs more
measuring).
• Connect one line (e.g. line B) to shield
from the other end of the bus cable. 
Measurement between the other line
(e.g. line A) and shield should give
some Ohms.
D
2
C
D
2
H
P
L
C
SHD
B
A
11k
Ω
Rmeas=Rwire+RSHD
D
2
C
D
2
H
P
L
C
5.0
Ω
SHD
B
A

17-Jul-23 14
Wire broken:
and B should be some kilo-Ohms
(normally OK value  needs more
measuring).
• Connect one line (e.g. B) to shield from
the other end of the bus cable and
measure between the line (B) and
shield.
– If resistance is large (kΩ) the line (B) is
broken.
D
2
C
D
2
H
P
L
C
Rmeas=Rwires+RD2C||RD2H
SHD
B
A
15k
Ω
D
2
C
D
2
H
P
L
C
55k
Ω
SHD
B
A
Rmeas=Rwire+RD2C||RD2H+RPLC +RSHD

17-Jul-23 15
Wire short-circuit:
and B should be some Ohms (wire
resistance in parallel with device
resistances).
• The place of short-circuit can be found
by using termination to cut out parts of
the bus.
– If termination is switched ON before
short-circuit measured value will be
about 220 Ω.
– If termination is switched ON after short-
circuit measured value will be some
Ohms.
D
2
C
D
2
H
P
L
C
SHD
B
A
3.0
Ω
D
2
C
D
2
H
P
L
C
SHD
B
A
221
Ω
Rmeas=Rwires+RTerm||RD2C
T

17-Jul-23 16
Line short-circuit to shield:
and B should be some kilo-Ohms (OK
value  needs more measuring).
• Measured resistance between short
circuited lines (e.g. B and shield)
should be some Ohms.
D
2
C
D
2
H
P
L
C
SHD
B
A
15k
Ω
D
2
C
D
2
H
P
L
C
SHD
B
A
1.4
Ω
Rmeas=Rwire +RSHD

17-Jul-23 17
Shield broken:
and B should be some kilo-Ohms (OK
value  needs more measuring).
• Connect one line (e.g. B) to shield from
the other end of the bus cable and
measure between the line (B) and
shield.
– If resistance is large (MΩ) then shield is
broken (if line B is OK).
D
2
C
D
2
H
P
L
C
SHD
B
A
D
2
C
D
2
H
P
L
C
SHD
B
A
9M
Ω
15k
Ω

17-Jul-23 18
Profibus DP Troubleshooting ABC Signal
level troubleshooting 1/2
• Profibus signal propagation (travelling)
delay in copper wires is about 4.2 ns/m.
• Using this information the distance to a
reflection source (short-circuit, open
circuit, faulty device…) can be
calculated:
0
ns
420
ns
0
ns
420
ns
100 m
Meas. Time = T
9
9
10
4
,
8
10
2
,
4
2












T
T
Distance

17-Jul-23 19
Profibus DP Troubleshooting ABC Signal
level troubleshooting 2/2
• The measured signal form depends on both the measuring place and the
reflection place.
• When measuring from the same side of the problem as the signal source
the reflection can be seen.
SOURCE
T=250 ns
PROBLEM
BOUNDARY
30 m
Distance =T/(8,4*10-9)
=250* 10-9/(8,4*10-9)
=30 (m)

17-Jul-23 20
Troubleshooting checklist 1/2
• Termination
– If communication problems arise, always check terminating resistors first.
– Termination should be turned on from both ends of every segment.
– Draw the bus topology in way that every segment can be easily seen or follow
the bus cable from one end to the other.
– Be careful with the sub-D connector terminating switch.
• Sub-D connectors:
– Often cabling problems are found inside sub-D connectors.
• Air gaps
– Air gaps between power lines and bus cables should be large enough (>20 cm).
– Air gaps between control signal lines and bus cables should be large enough
(>10 cm).

17-Jul-23 21
Troubleshooting checklist 2/2
• Cabling rules
– Segment cable lengths should be according to Profibus standard (1500kbit/s
max 200m).
– Stub line lengths should be according to Profibus standard (1500kbit/s max
6,6m).
– 1 meter rule should be observed.
– Grounding should be correct.
• Masters and slaves should be configured correctly.
• All devices connected to the bus should be operating and undamaged.

Profibus DP Troubleshooting - Kone cranes Rev 1507.pdf

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