ExcelPTZ PTZ605 series Manual de instrucciones descargar pdf (Pagina 11)

such as domes 3 and 5 in the following “Star diagram”. Note that all the other domes do not have the

120ohm resistor connected. The resistors are already fitted to the domes PCB but by default are not in circuit.

To put them in circuit you must move the small “jumper” as previously indicated.

As the star configuration is not in conformity with the requirements of RS485 standards, problems such as

signal reflections may arise, especially when there are long cable connections. The results are that control

signals are decreased and the dome may not respond to, or just responds intermittently to the controller.

If your STAR circuit is not too extensive

with each spur in the region of 20-50 metres

you can expect quite good reliable

performance using this technique. If you

experience any problems though, there is a

RS485 distribution box available CODE

PT750 to help overcome any problems.

Overcoming RS485 data loss using an RS485 distributor

In the real world not everything always works exactly as it’s expected to!

RS485 data signals that control the domes’ movements are tiny signals that can get corrupted for many

reasons. Poor cable quality, not using a PAIR of cores from a CAT5 but using one core from TWO separate

pairs, running the CAT5 cable near mains equipment such as fluorescent lighting all will have a detrimental

effect on the signal. These are things that you can correct with good installation practices.

Where you wish to run several separate CAT5 cables out to send the RS485 data signal out to the domes you

are in effect correcting the STAR method of RS485 data distribution. As previously mentioned the problem

with the Star method is that it is not actually designed for RS485 but generally works okay if you follow the

previous notes on getting the 120ohm resistor setting right, as per the previous notes.

One way that takes the guesswork out of installing the Star method is to utilise an RS485 distributor. This has

the advantage that the RS485 signal is correctly distributed to the domes so that they behave as expected.

You can create up to 4 spurs to the domes and put up to 4 domes on each spur. Just like the Daisy chain

The Star circuit for wiring PTZ’s.

The two furthest domes need the 120ohm

resistors enabling, by moving the “Jumper”

In this example it’s domes 3 &5.

The Star Diagram

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ExcelPTZ PTZ605 series Manual de instrucciones Pagina 11