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LOOKING THROUGH THE INTERNET

A Prototype Security System
by Skylar Lei, Jim Haslett, and Mike Smith

Start • Web Server Choice • Interactive GUI • Video System • Remote Camera System • Control RF Link • Solar Power Module • • Sources

VIDEO SYSTEM

With all the necessary software in place, let’s look at the hardware used in the base station. Any commercial capture card that is capable of taking analog NTSC signals for the display of the real-time video would meet the project requirements. We chose the inexpensive Aver EZCapture card.

A video-switching module was developed to select a particular camera’s video signal on request. Figure 2 shows the entire switching module. The analog video MUX (LT1204) has a bandwidth able to handle video signals with minimal distortion.

(Click here for figure)

Figure 2—Here’s a look at the switching module that controls multiple video streams from the remote camera system via RF control links.

This switching module receives information from the base station through the serial port for transmission to the remote camera system. A voltage level shifter (MAX232) reduces the serial communication ý25-V signals to the logical TTL level required by the logic interface in the camera system. The COM8017 converts the switching information from a serial to parallel datastream. Some of these bits are used to control the analog MUX chip (LT1204). Other bits control the remote camera system.

When the base station starts up, the Microsoft operating system interrogates possible devices during a serial port test. These signals can make the switching module unstable. The test signals were blocked using a simple 27-s delay implemented via counters, and activated by the serial line DTR signal from the base station.

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