14
RS485 connection
-
Connecting the Keypad or DVR to the Dome
.
The dome is controlled by an RS485 data signal that is given by either a KEYPAD or a
suitable DVR. This data signal tells the dome to pan, tilt etc. Its important that you
read the early section of these instructions to understand the fundamental principle of
RS485 cabling techniques so that you get it right.
RS485 has two cores, A and B or sometimes known as RS485 + (A) and RS485 – (B) if you get these two
the wrong away around then you will not be able to control the dome. Sometimes installers get the
connections right on one dome but not on the other and find only one dome works. They then swap the wires
around at the keyboard only to find out one dome has now burst into life and the other one now fails!! But
they don’
t put 2 + 2 together and realise their mistake that they have wired one dome different to the other.
Take great care getting these the right way around and make sure you wire each dome IDENTICALLY so
that if you have to swap the A & B lines over at the keyboard you know all domes are wired the same!!
The PTZ200 series adopts the following RS485
convention:
ORANGE = RS485 + or A
YELLOW = RS485 – or B
You should initially be wiring the dome to the keyboard or DVR on your workshop bench or at least your
kitchen table to prove you know how to get everything to work. Once you have done this, it is just a job of
extending the cables and physically installing the domes on site. You must obviously take note of the RS485
wiring techniques mentioned at the beginning of these instructions and get the 120ohm resistors correct in
the “End of line” domes. Generally speaking you will always be extending the RS485 signal from either the
keypad or the dome using a CAT5 or similar cable.
The Keyboard models type CCT786 & CCT768 are supplied with a connecting
lead and a break out box that looks like the following picture.
The RJ45 lead supplied with the keyboard connects into the rear of the keyboard
into the slot marked “OUT” do not connect it to the “IN” position by mistake.
This lead provides the RS485 A and RS485 B connections from the keyboard. It is this
cable that you would extend using 1 pair of conductors from a CAT5 cable. To test the
dome on your workbench you can obviously omit the “extension” cable as the dome
and keyboard are next to each other.
Now connect the RS485 data cable to the breakout box. Note that the orange
connection is the RS485 + A Line connection and the yellow is the RS485 – B Line
connection. The following picture shows the breakout box with the actual dome
connected straight to it. The orange of the dome connects with the orange of the
breakout box and the yellow of the dome connects with the white of the breakout
box.
Obviously if the dome was on site you could not connect it to the breakout box
directly. This is where you would use the CAT5 cable to connect the two together.
YELLOW
ORANGE
