Trouble to control 2 PTZ cameras with Controller and DVR

[Eurekabox 0]

Hi, My name is Roger. I'm from Mexico. And i have problems...

 

I have 2 PTZ cameras, model CNB SS2565nxw, 1 PTZ Controller model CNB SC3100 and 1 DVR Avtech AVC798ZD. The DVR was the last accquisition. I attached a diagram. I would have bought everything of the same brand, but CNB DVR cant be accesed from Safari or Firefox browser (I have a Macbook pro and i'm tired of using a virtual machine to run windows XP, to run Internet Explorer), and Avtech DVR does.

 

1. The cameras and the controller work well, from every camera goes a utp cable up to the controller. Movement is smooth, exact.

 

2. If i connect the RS485-PTZ cable from the DVR to existing RS485 network i have with the controller and the 2 cameras; movement from the controller to the cameras goes crazy, inexact, slow, fast. erratic.

 

3. Movement from the DVR to the cameras is OK (an IR remote control is used to move the cameras, BUT this is NOT the MAIN way to do it: at server site the PTZ controller is always used and not the DVR). If i disconnect the DVR-PTZ cable, it goes back to normal.

 

3. I'm connecting the DVR-PTZ cable to my existing RS485 network because i want to be able to move the cameras from the web portal of the DVR (when im not at server site).

 

So what is wrong?

 

Thank you.

[craiga 0]

Hi,

It's hard to tell from your description whether the RS-485 network is a straight line -- although it looks like it could be. RS-485 requires that you use wiring that goes from one device to the next device to the next device to the last device. You can't connect wiring in a way that forms a T or a Y or a star at any point.

 

You also need to have termination resistors (100 ohms) at both ends (in parallel with the devices on each end). Note there can be only two ends, if you have more ends, then the wiring is incorrect (you have a star, not a straight line). Your diagram is certainly not correctly terminated -- place a 100 ohm resistor across pair close to the connector to the AVTech DVR and turn off termination on the SC3100. You also need to have a termination turned on on the last camera -- from the diagram this doesn't appear to the the last camera (but it's not clear the wiring is a straight line).

 

Note that most DVRs are in star networks with a cable leading from the DVR to each camera. You simply can't connect up RS-485 in the same way (and expect it to work). However you can use two pair (one going to the camera and one coming back from the camera) to ensure you keep the straight line wiring required by RS-485 even though the physical cabling is a star.

 

-Craig

[Eurekabox 0]

Hi Craiga

 

thanks for your help. 2 months later... hehe

 

And yes mi cabling makes a star, one cable from the joystick... and the cables from the cameras and dvr joins at some point to the joystick cable.

 

Can you point me to a webpage that shows the resistor you are talking about? and how to place it on the cables?

 

[Soundy 1]

You can't simply parallel controllers on a serial line. You need this type of device to allow them to get along cleanly: http://www.bb-elec.com/product_family.asp?FamilyId=31&TrailType=Sub&Trail=93