Ø
Problems in practical connection
In some circumstances user adopts a star configura-
tion in practical connection. The termination resistors
must be connected to the two equipment 1# and 5# in
picture 9-4.4. As the star configuration is not in confor-
mity with the requirements of Rs485 standards, proble
such as signal reflections, lower anti-interference
performance arise when the cables are long in the conn-
ection. The reliability of control signal is decreased
with the phenomena that the dome does not respond to
or just respond at intervals to the controller, or does
continuous operation without stop.
ms
Trouble
Possible cause
Solution
Dome can
self-testing
but cannot
be controlled
The dome can
be controlled
but the operation
is not smooth
1. Change the address and baud rate of controller
or dome
2. Adjust the + and -connection of Rs485
3. Make sure the connections are fully seated
4. Change RS485 Bus wires
1. Secure the connection
2. Replace RS485 bus wires
3. Add termination resistors to the system
4. Install RS485 distributor
Ø
RS485Bus troubles solution
RS485 distributor
Picture 9-4.5
Picture9-4.4
In such circumstances the factory recommends
the usages 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 transmission.
(Refer to picture 9-4.5)
1. The address and baud rate setting of dome.
are not in conformity with the controller.
2. The + and - connection of RS485 Bus is incorrect.
3. bad connection.
4. there are circuit in the RS485Bus.
1. the RS485Bus is not in good contact with
the connectors.
2. One wire of Rs485 bus is broken.
3. The dome is very far from controller.
4. There are two many domes connected in the system.
36
Appendix