Rs-485 Connections, What's This For Exactly?

[kuchars22]

Hi all,

I've a Vista all-in-one camera, and has several leads on it as follows:

GND

+

-

EXT2

EXT1

RS-485 +

RS-485 -

Focus

Common

Zoom

The instruction manual says that it can be controlled by an RS-485 system via the RS-485 wires, but doesn't say what can be controlled. The camera doesn't have Pan or Tilt, but has zoom and focus facility built in. There is already a seperate wire for focus and zoom, and the camera came with a remote control to connect to the camera, but there is nothing in the manual that mentions this so I'm not entirely sure how to connect this up (I'm guessing the remote control connects to the Focus and Zoom wires). Am I right in thinking that the RS-485 controller can zoom and focus, and the seperate remote control can do the same if connected to the Zoom and Focus wires on the camera?

Lastly, is the RS-485 connector the same as an RS-232, as I'll need to get one from Maplin?

thanks

[Bill]

Hi

Typically, RS485 is used for telemetry in CCTV systems - so your assumption on that basis is correct. It would most probably allow control of the zoom and focus remotely via one of the multiplexers also manufactured under the Vista brand.

RS485 is a serial protocol, and is an "open" porotocol, meaning that anyone who wants to use it, can. It was developed because of the limitations of RS232, primarily the distance over which the protocol works reliably. RS485 can operate over roughly a kilometre (often a bit more) whereas RS232 is not reliable after as little as 2 metres.

THe distance allowed makes RS485 an easy and sensible choice for sending telemetry signals around a CCTV system.

Full telemetry will offer control of far more than just zoom and focus - for example, pan, tilt, wash, preset guard tours, and so on. This depends on the camera and hardware as much as the protocol used to send the signal though - as well as the features the controller and software offer.

RS485 is most commonly terminated using a DB9 serial plug, but increasingly seems to be terminate dusing RJ45 (the same as ethernet) - in any case, Maplin will have the correct "end" for you.

Bill.

[kuchars22]

Hi

Typically, RS485 is used for telemetry in CCTV systems - so your assumption on that basis is correct. It would most probably allow control of the zoom and focus remotely via one of the multiplexers also manufactured under the Vista brand.

RS485 is a serial protocol, and is an "open" porotocol, meaning that anyone who wants to use it, can. It was developed because of the limitations of RS232, primarily the distance over which the protocol works reliably. RS485 can operate over roughly a kilometre (often a bit more) whereas RS232 is not reliable after as little as 2 metres.

THe distance allowed makes RS485 an easy and sensible choice for sending telemetry signals around a CCTV system.

Full telemetry will offer control of far more than just zoom and focus - for example, pan, tilt, wash, preset guard tours, and so on. This depends on the camera and hardware as much as the protocol used to send the signal though - as well as the features the controller and software offer.

RS485 is most commonly terminated using a DB9 serial plug, but increasingly seems to be terminate dusing RJ45 (the same as ethernet) - in any case, Maplin will have the correct "end" for you.

Bill.

Thanks, Bill.

Am I right that you can actually use Cat5e ethernet cable to wire to DB9? My DVR is an old Cop 15-VP with DB9 connecter.

Thanks again

[Bill]

Hi

Yes you could - RS485 requires four wires and a ground for what is termed "full duplex" - which is to say data travelling in both directions at the same time. It only requires two wires and a ground for "half duplex" - data only travelling in one direction at a time.

As with any serial protocol, there are transmission and receive terminals - generally, you need to ensure that e.g. transmit on the mux goes to receive at the camera, and vice versa - if you send a transmit data to a transmit terminal at the other end, nothing will happen.

Cable type only really becomes an issue where distance is significant, in which case there are many specialist cables out there with very specific characteristics for that purpose (Belden types or equivalents) - but for RS485, CAT5e should be fine up to a couple of hundred metres or so, possibly more. Just try not to run it close to mains cables for any distance, as it may induce AC which can affect the video feed - often causing "hum" or white rolling banding on the video.

Have you got a wiring diagram in your manual for the RS 485 terminations?

Rgds, Bill

[kuchars22]

Hi

Yes you could - RS485 requires four wires and a ground for what is termed "full duplex" - which is to say data travelling in both directions at the same time. It only requires two wires and a ground for "half duplex" - data only travelling in one direction at a time.

As with any serial protocol, there are transmission and receive terminals - generally, you need to ensure that e.g. transmit on the mux goes to receive at the camera, and vice versa - if you send a transmit data to a transmit terminal at the other end, nothing will happen.

Cable type only really becomes an issue where distance is significant, in which case there are many specialist cables out there with very specific characteristics for that purpose (Belden types or equivalents) - but for RS485, CAT5e should be fine up to a couple of hundred metres or so, possibly more. Just try not to run it close to mains cables for any distance, as it may induce AC which can affect the video feed - often causing "hum" or white rolling banding on the video.

Have you got a wiring diagram in your manual for the RS 485 terminations?

Rgds, Bill

Unfortunately not in the manual for the camera. I need to have a look on the PTZ setup commands on my DVR when I get home. It doesn't go into that on the DVR manual. The camera can accept RS232 commands, Norbain RS485 and Pelco D and P. Do I setup the protocol according to what the DVR can support?

Thanks

[Bill]

Sure thing.

You will probably find that it is half duplex, which would mean on a 9 pin to 9 pin lead, you'd connect pin 2 (tx) at one end to pin 3 (rx) on the other, pin 3 to pin2, and pin 5 to pin 5 (ground).

I don't know the specific camera, but will have a browse in due course to see what's in my library.....

Regards,

[arfur mo]

Sure thing.

You will probably find that it is half duplex, which would mean on a 9 pin to 9 pin lead, you'd connect pin 2 (tx) at one end to pin 3 (rx) on the other, pin 3 to pin2, and pin 5 to pin 5 (ground).

I don't know the specific camera, but will have a browse in due course to see what's in my library.....

Regards,

to add to what Bill has said,

you may need to set the termination at the camera for the comms to work properly, many come unterminated. there is a removable jumper as found in computers which needs to be made (shorted).

your DVR will likely have many protocols as will the camera, Pelco D is the one i would start with and it has to be the same for camera and DVR.

regs

alan