application note 4

  PC Based DVR Pan/Tilt/Zoom System

  Adding a low cost Digital Video Recorder (DVR) to a PC is a fairly simple process.  This application note shows how a simple system can be setup using an Antona RS232 to RS485 converter to control the video camera motion pan, tilt and zoom (PTZ or Pan/Tilt/Zoom).  The recorded video picture output played back from the hard drive is perfectly good for the applications below:

  • PC based Digital Video Recorder (DVR) - Surveillance for 24 hour recording to a disk drive of video inside rooms and outside areas (parking lots, drive up windows, etc.).  Audio can be recorded with the video.
  • Instructional video - where a computer is used as a DVR to generate and play short video segments directly on the computer display as part of the lesson.
  • In motion picture and video production - used to preview scenes before shooting or piggybacked with shoots to edit and view immediately.
  • Desktop Surveillance/Security/Locating system - a computer monitor on a receptionist's desk can be switched to display several remote video camera locations.  A simple setup can display and record activity from the lobby to the loading dock, locate individuals on the premise or even help secure an area of restricted access.

  The electronics for this example system consists of a Q-See Digital Video Recorder (DVR) PCI card, a dome model pan/tilt NTSC video camera made by AccuDome, 2 – 75 ohm to 120 ohm BALUNs, a 60 foot length of CAT-5 cable and our ANC-6185T RS232 to RS485 adapter.  Software for the application is included with the DVR card. The software represents much of the look and feel of the final system and its operation.

 Installation and Setup

The author recommends connecting the pieces together before doing a permanent installation.  That will save a lot of time later if there is a problem with the hardware.

Installing the PCI DVR card into the computer is the first step.  Follow the instructions that were included with the DVR card.  This mostly means turning the computer off (unplug the 110VAC cord), removing the PC cover to access an empty PCI slot on the motherboard.  After the card is installed the user powers up the computer, and installs the application software included with the card.  I found that going to the manufacture’s website beat loading the software included with the card. That is because a newer software version was available for download and installing it required un-installing the older software version included with the DVR card.  Getting the DVR card and software working in your PC is 90% of the system.  A special note about the DVR card used in this application: the card requires a specific set of hardware and software for operation.  The requirements include Windows 2000 or XP running on an Intel Pentium 3 at 800MHz (minimum) with a NVIDIA Geforce 2 VGA compatible monitor controller card.  An 80 GB hard drive is recommended also.  The author setup the system as described on a Dell Dimension 3000 using the ‘stock’ features that came with the computer.

The dome pan/tilt camera is setup next.  The author set the camera on top of the PC (powered off) for a quick test of the interface in operation.  Setup the PTZ device code (address), protocol and serial communication speed on the camera’s internal bit switches.  That sounds a lot harder then it is.  Set the device code (camera address) to 1, the protocol to ‘Pelco-D’ and the baud rate to 9600 by matching the DVR manual table entries to the camera bit switches.  Remember, the idea is to get the interface working, not to break speed records for how fast you can transmit commands to the camera or set up a final camera address.  Pelco-D and Pelco-P protocols are supported by most of the DVR cards on the market in the United States (same goes for the PTZ cameras).

  Using a short RG-59 BNC male-to-male cable, connect the video output signal BNC coax from the camera to the topmost DVR card’s BNC connector for camera #1 input.
For the final installation use two BALUNs as shown in the figure above to convert the NTSC 75 ohm impedance to (and from) the 110 ohm impedance of the CAT-5 cable.  If you are only running the camera 20' or less away, you may be able to just run RG-59 (75 ohm) coax between the camera and DVR card.  On this particular make/model camera, I was able to remove the camera end BALUN from its plastic case, and install it inside the camera's mounting bracket for a clean looking install.

  Configure the ANC-6185T adapter for AutoXmit 2-wire communication with the 120 ohm terminating resistor enabled (JP4 in ANC-6185 Manual).   Next is to connect the ANC-6185T to the camera RS-485 data+ and data- lines to the adapter TX+ and TX- lines respectively and plug the adapter into the mating serial port connector on the back of the PC.  The external camera power supply should be plugged in last and the PC powered up.

Start the DVR card application software.  With the Q-See card, the application is called ‘SuperDVR’ and is user friendly for setup.  When the main page comes up, the output from the video camera should be displayed in the upper left of the display.  First you must unlock the software to make any changes.  To do this, click on the padlock button icon and then click on the ‘OK’ button without entering a username or password.  Now, from this same screen, you click the wrench button icon (configuration) on the lower right hand side of the screen.  That brings up a new screen for setting system configuration.  Clicking on the dome camera button icon brings up the next screen.

  Fill in the settings as shown for setting the PC’s serial port to 1, 9600 baud, 8 data, no parity and 1 stop bit.  Output will be by Pelco-D protocol to the camera addressed as #1.  These settings for protocol and baud rate match what we have set the camera to.  The number of data bits, parity and stop bit number is fixed on this particular camera.  The serial port number may be different on your system, and of course, depending upon your PTZ camera and addressing any or all of the above may be different.  It is easier to make setting changes on this screen then on the camera, so take care that the camera settings are correct.

 To test the PTZ functioning, click on the up-arrow button icon (return) to get to the main screen again.  The lower right hand button of a direction diamond button icon is clicked to bring up the pan/tilt/zoom screen.  Clicking on a directional segment of the largest icon should cause the camera to move in that direction.  Zoom functions are located below the directional diamond, but the AccuDome model used does not have the zoom electronics.

For permanent installation, follow the instructions included with the camera before mounting the camera to the ceiling or wall.  If you are installing multiple PTZ cameras be sure to enable the 120 ohm terminating resistor in the last camera on the CAT-5 cable.  More about that under ‘RS-485 Interfacing’.  The AccuDome camera used in this note is pan and tilt only.  The price for a pan/tilt/zoom video camera is between $500 and $900 compared to $200 for this model.  What you pay for a camera is completely application driven.  If you are monitoring a parking lot, the camera price could be well over $1,000 for an outdoor PTZ metal enclosed camera.  A stationary video camera with microphone to focus on an enterence door is available for under $100.

RS-485 Interfacing

The Antona ANC-6185T or ANC-6185R provides the electronics to convert the serial RS232 comport on the PC into RS485 noise immune serial signal to control multiple video camera’s pan/tilt/zoom operation.  This is because RS485 type interfaces can be ‘daisy chained’ from camera to camera.    Note that the last camera in the chain should have a 120 terminating resistor installed across the plus and minus data lines.  That also means that the Antona adapter should have JP4 set to enable the on-adapter 120 ohm terminating resister at the beginning of the chain as described above.  Each camera has a user set unique address so that only the selected camera will be pan/tilt/zooming.  The camera will have 1 or 2 sets of bit-switches that are set for the individual camera device code and communication set-up as described in the ‘Installation and Setup’ section above.

Additional Software Setup

The system operation is defined by the software included with the DVR card.  In the initial software setup, the user selects which camera to control, what conditions should trigger recording on each camera, type of alarm if a camera is set to detect motion and the PC screen display.  Setting the physical camera number is simply a matter of which BNC input connector is used for video input.  On the DVR card used by the author, the topmost BNC input is camera #1.  The 2nd from the top is camera 2, etc.  That identifies which camera to select for controlling.  The user sets the PTZ camera being input on the #1 (topmost) BNC video to be associated with the #1 pan/tilt/zoom control channel.  Only one Antona adapter is needed to control 16 pan/tilt video cameras.  Controlling more then 1 to 3 video camera almost certainly would require externally powering the Antona adapter unless the cameras were only a short distance away from the PC.  The DVR card has 4 channels of video input (1 camera recording channel can accept audio).  Four channels is probably enough to handle a small home or business.  You can add 4 more video channels by installing a 2nd DVR card.

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Updated 04/24/09 12:00

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