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CCTV's workhorse.

SOME OF THE BEST HORROR stories in the industry are about CCTV installations that required pan/tilt motors. They freeze, get tangled in their own cables, lose their mechanical stops, and eventually develop cable fatigue.

Indoors, these pieces of ingenuity are undergoing major improvements, mainly due to the development of smaller cameras and customers' desire for smaller, less conspicuous surveillance equipment. Outdoor pan/tilts, however, are a different story.

For the abuses these motors encounter, it's amazing how well they endure. However, there is always room for improvement. To understand why an outdoor pan/tilt can be a servicing nightmare, consider some common problems.

For example, is the control/video cable dressed and secured properly to allow free movement of the motor? This important step is often overlooked. Normally, the video coax cable, multiconductor zoom-lens control cable, and power cord are panning with the camera. The control cable for the pan/ tilt is usually stationary, entering at the base of the motor. That's a lot of cable and can result in a stiff tie-wrapped bundle for the motor to move, especially if you have an autopan installation. The result: cable fatigue or a bad picture on the monitor.

With indoor equipment, some motor manufacturers are switching to cable feed through, in which all control cables enter the stationary base of the drive motor and feed internally, using several methods, to the head of the motor. Outdoors, however, equipment changes are slow in coming. If a drive motor doesn't have the feedthrough feature, it may be worthwhile to purchase a coiled video cable that combines video power for camera and lens control into one jacket. They are fairly inexpensive, easy to install, and as flexible as a phone cord. The nylon jackets used in manufacturing these cables are not affected by the sun's ultraviolet rays.

Wind and weight loading on the drive motor are other factors to consider. If the motor is going to be installed on a high roof in the Northeastern United States versus a parking deck in the Southeast, it makes a difference in the type of motor you should choose.

An important selection like this can only be made by the company purchasing the motor. Don't expect motor manufacturers to supply this information. Each will tell you about the maximum-load rating of a particular motor, then leave the important decisions up to you. For example, what should be allowed for gusty winds? How much should you add to the load rating for several inches of snow? Wrong answers mean the difference between profit and loss.

Don't just consider the weight of the camera, zoom lens, and housings. Nature can really play tricks with an outdoor motor in the dead of winter. An extra 10 lb. added to the rating of the motor for Mother Nature might just be money well spent.

A new style of pan/tilt designed to offset some of the problems caused by nature is now available. A side-mount pan/tilt reduces a significant amount of the wind and weight loading problems experienced with conventional, top-mount drive motors. In addition, troublesome mechanical stops have been replaced with electronics, resulting in less wear and tear on the motor. To better understand why servicing problems are reduced with the use of this motor, let's consider what nature can do to a motor.

The original, top-mount pan/tilt cantilevers the weight of the camera, lens, and housing in front of its body. (See Exhibit 1.) If the load is instead centered on the axis of the motor, in the side-mount position, tilting that load is a lot easier. (See Exhibit 2.) The motor doesn't need to have costly counterweights or internal springs to help it return to its neutral gravity position the top of the pan/tilt).

How about the wind? Consider the two shapes (exhibits 1 and 2). The higher the profile, the more wind loading. Conversely, the lower the profile, the less wind loading. The side-mount version has a lower profile.

Let's suppose you want to mount a motor upside down. With the side-mount equipment, all that is required is for the mounting arm to be reversed. With the top-mount units, the counterweight (which you have just bought) and some springs usually have to be removed before the motor can be inverted. These complications cost money.

Another advantage of side-mount motors is that they use electronic stops rather than mechanical ones. The motor travel is set on the pan/tilt, using a small screwdriver to set internal potentiometers. Now, rather than a hard mechanical reversing, which a motor normally experiences, the voltage cuts off electronically when it reaches the set limit (for both horizontal and vertical movement). This feature will undoubtedly extend the life of the motor and eliminate serious motor downtime.

To eliminate the effects of wind and snow on drive motor gears completely, consider switching to an outdoor, environmental-domed housing. Now, everything is protected from the wind.

Since so much of the load is taken away from the drive motor with a domed housing, indoor motors can be used outdoors. Enough room should be allowed for the camera and lens when ordering a domed housing.

If properly selected and correctly installed, a pan/tilt motor should provide years of trouble-free operation. Manufacturers have made some serious advances in the design and mechanical features of this equipment. The rest is up to you.

About the Author . . . Raymond V. Pagano is president of Videolarm Inc. in Lithonia, GA.
COPYRIGHT 1990 American Society for Industrial Security
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Lights! Camera! Action! supplement; closed-circuit TV in security systems; pan/tilt motor
Author:Pagano, Raymond V.
Publication:Security Management
Date:Mar 1, 1990
Previous Article:I spy.
Next Article:New challenges in technology transfer.

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