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Pan/Tilt/Zoom Cameras & RS-485

When you are looking for a camera solution, whether it is for personal or business use, it can be a daunting experience when dealing with PTZ (Pan/Tilt/Zoom) cameras. For most people, the additional RS-485 wiring necessary to run to the cameras can be confusing and when you start talking about protocols and baud rates, many people will avoid purchasing or installing a PTZ device altogether even if it is a necessity. I will explain some of the basic features of the cameras and step you through the setup of an RS-485 controller and camera, though please keep in mind that, with any given controller or camera the individual adjustments to the settings will differ. Your manual will always be your best resource for information. With this information in front of you, you can have your PTZ camera set up in just a few minutes.

The first thing to note about a PTZ camera as opposed to a fixed camera is the freedom of movement you get. When you are finding that a camera’s static position isn’t getting the coverage you need, a PTZ camera fixes the problem by simply allowing you to change the direction it’s facing as well as zoom in to take a closer look at the situation. Walk into any electronic store, look up and you will probably find yourself looking at a PTZ camera. It’s useful for following a suspect around and seeing what they are holding in their hands. This makes it a perfect choice for many situations. Another advantage of using a PTZ camera over a fixed camera is the zooming ability. While your recording unit will often have a digital zoom capability, it can make the image look blocky and unusable. Many PTZ cameras have optical zooms as well as digital zooms that can greatly increase the viewing distance with the same image quality regardless of how close you get to the subject.

When you first open the box of your PTZ camera, you may find that there are many dipswitches and wires. Don’t panic. They are all easily explained and with a little knowledge, it becomes a simple matter to figure out what goes where. I’ll start with the wiring. The standard video and power cables will be there but you will also have another for the RS-485 control. This is usually a 2-wire set that allows you to control the camera’s movement and zoom capabilities, though some devices support 4-wire RS-485. Again, don’t panic. 4-wire RS-485 can be configured as 2-wire. In a 2-wire setup, one wire will be the positive (d+) and the other the negative (d-). The camera’s manual will guide you on which are which, whether they are separate colors or if one has an indicator stripe, etc. Pay attention to this as setting up the wires incorrectly will mean that your camera will not PTZ even with everything else set up properly. These wires will be run directly into your controller or even your DVR if it has RS-485 capability. By setting up with both a controller and your DVR you will be able to access the controls with either unit, allowing you to control the camera(s) remotely from anywhere in the world if your DVR supports networking and you have your DVR configured correctly to the internet.

The various dipswitches that you find are intended to set the address, the protocol (if multiple protocols are available), and the baud rate (again, if available). RS-485 allows for up to 256 devices to work simultaneously on the same 2-wire or 4-wire bus. In order for this to work, each device (including the controller) must be assigned a unique ID. This allows you to select which device you wish to work with when controlling them. Device IDs are numbered 0-255 and you’ll need to assign each camera its own unique number taking care not to use the ID assigned to your controller or DVR.

The protocol is simply the language that that particular camera is using. There are too many protocols to list them all here but most DVRs and PTZ controllers will support the Pelco-D or Pelco-P protocols and every PTZ camera, controller, and DVR we select for our product line holds true to this. You may find that your camera has many different protocol selections available so pay attention to the diagram showing you how to select the proper one. This is important to note because you may find that your camera uses a proprietary protocol and will not be compatible with certain devices or vice versa.

The baud rate is the speed at which the camera receives the information. This will usually be 2400-9600. The key to ensuring proper functionality with the camera’s controls is to make sure that all of your selections match up with the device controlling it. For instance, if you have set your camera to address #1, the protocol to Pelco-D, and the baud rating to 2400 you will then need to set the controller to those settings as well. If not, you will not be able to control the camera. PTZ cameras as well as controllers and DVRs often come preset with a default setting, in most instances this will be Pelco-D at 2400 Baud.

For accuracy of this article, I will also include the following information. It is understood that the RS-485 data cable will have a ground shield for long distance runs. This will be one twisted wire pair plus the Ground. Depending on your device or system you may have the ability to change the Data Bits, Parity, and Stop Bits. If this is the case, you need to comply to the full protocol which is typically 8 Data Bits, no Parity, and 1 Stop Bit.

Now that you have a basic understanding of your PTZ camera, you should have no problem with setup giving you more time to start testing out its capabilities.

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Submitted by Tony M. - 3/4/2009 @12:07pm

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23228 Views      |      2 Comments Post Comment
Submitted by Anonymous - 08/28/2012 07:19:00 AM
I will like you to explain more on the dip switches
Submitted by asawant - 02/28/2011 01:27:13 AM
exelent and easy to understand this artical

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