THE MAGAZINE FOR COMPUTER APPLICATIONS
Circuit Cellar Online offers articles illustrating creative solutions
and unique applications through complete projects, practical
tutorials, and useful design techniques.

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

SOLAR POWER MODULE

Our solar power module consists of three components: a solar panel, a rechargeable battery, and a voltage regulator. Together they supply steady power for the camera, video transmitter, and control-signal receiver. The power module is almost maintenance free, except for the battery. Our prototype used a standard car battery. However, this battery will not last long with the deep-cycle usage of the remote operating conditions, which swings from near full charge to almost zero charge (expected under cloudy conditions).

Because the solar panel sits outdoors all the time, it must be weatherproof and corrosive-resistant. The panel must also be able to produce enough current to recharge the battery. We chose the model 500-12V from Sun-Mate, which came with a built-in blocking diode in its circuit to prevent a reverse flow of electricity from the battery.

As the power output of the solar panel depends on the light intensity, its output is expected to deteriorate during sunrise, sunset, or cloudy days. A simple trick to optimize the solar panel is to place two inclined mirrors beside it to reflect more sunlight onto the solar panel (see Figure 4). We found that an angle between the panel and the mirror of about 165ý for the latitude of Calgary (51ý) produced an increase in performance of 10–25%.

Figure 4—Power availability can be improved by 20% when two inclined mirrors are used to reflect more sunlight onto the solar panel.

LIMITATIONS

With the software and hardware described above, we were able to build a prototype Internet-based security system. The remote user connects to the web server at the base station using a browser and specifies the view from a local or remote camera using the GUI.

The prototype has some limitations. The current system can only support one user at a time, either locally or remotely. There will be race conditions if squabbling siblings try to control the camera system at the same time. There are no remote diagnostic capabilities built into the software if a remote component fails. Also, the prototype does not have the functionality of saving video clips that show what happened while the user was not logged in.

New challenges to be met by next year’s Project Teams include modifying the web-based GUI to remotely rotate and zoom the cameras in and out. Custom RF transceiver designs could also reduce the cost of the video system. In addition to those ideas, improved handshaking between the base station and remote cameras would be a definite advantage. However, that would take away our excuse that it’s necessary to take time off from work and go up to the mountains to restart the system!

PREVIOUS • NEXT

Circuit Cellar provides up-to-date information for engineers. Visit www.circuitcellar.com for more information and additional articles.
For subscription information, call (860) 875-2199, subscribe@circuitcellar.com or subscribe online. ýCircuit Cellar, the Magazine for Computer Applications. Posted with permission.