Rs485 Bus Faq - Dahua SD42C Series Installation Manual

7.4 RS485 Bus FAQ

Phenomenon Possible Reasons

Speed dome
can run self-
diagnosis but I

cannot control
it.



I can control
the speed
dome but is not

smooth


Host address(baud rate) and
speed dome address(baud rate)
are not match;
Positive and negative end of
RS485 Bus are misconnected;
Connection cable is loose；
RS485 Bus connection are cut
off;
RS485 Bus connection are not
good；
One RS485 bus is off；
The distance between host and
speed dome is too far；
Parallel connected too much
speed domes.
Figure 7-2
Solution

Modify host or speed dome setup ；

Switch RS485 positive end and
negative end；

Fix connection cable firmly；

Replace RS485 Bus.

Connect RS 485 Bus again；

Replace RS485 Bus；

Add terminal matching resistance；

Add RS485 distributor.
22