Ø
Problems in practical connections
In some circumstances user adopts a star co-
nfiguration in practical connection. The termina-
tion resistors must be connected to the two equi-
pment 1# and 5# in Picture 9-6.4. As the star con-
figuration is not in conformity with the require-
ments of RS48 5 standards, problems such as sig-
nal reflections, lower anti-interference perform-
ance arise when the cables are lon g in the conne-
ction. The reliability of control signals is decrea-
sed with the phenomena that the dome does not
respond to or just responds at intervals to the co-
ntroller, or does continuous operation without
stop.
Trouble
Possible cause
Solution
Dome can do
self-testing
but cannot be
controlled
The dome can be
con trolled but
the operation is
not smooth.
A
Secure th e conn ection
B
Re place R s485 B us Wi res
C
Ad d term ination resist ors to t he sys tem
D
Ins tall Rs 485 di stribut or
Ø
Rs485 Bus troubleshooting
Rs485
Distribu tor
B-
1#
2#
3#
120
120
120
A+
1#
32#
1 5#
6#
Main contr oller
Picture 9-6.4
P ictu re 9- 6.5
1 20
120
A
T he Rs4 85 Bus line is n ot in g ood
conta ct with the con nector s.
B
O ne wire of the Rs485 Bus is
broke n.
C
T he dom e is ver y far fr om
contr oller.
D
T here ar e too m any domes
conn ected in the sy stem.
A
The address and baud rate setting of dome
are not in conformity with those of controller.
B
The "+" and "-"connection of Rs485 Bus is
incorrect.
C
The dome is very far away from controller.
D
There are too many domes connected in the
System.
A
Change the address and baud rate of controller or dome
B
Replace Rs485 Bus wires
C
Make sure the connections are fully seated
In such circumstances the factory recommends
the usage of RS485 distributor. The distributor can
change the star configuration connection to the mode
of connection stipulated in the RS485 standards.
The new connection achieves reliable data transmi-
ssion. (Refer to Picture 9 -6.5).
41
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