Contributor: Video Experts
The latest wave in CCTV systems is the miniature dome camera. Why settle for a fixed field of view when you can go for 360°? Not to mention up and down. These feature packed little miracles of modern technology when correctly installed can provide many years of dependable service. « Correctly installed » is the key word here!
Lately almost every other technical call received at our service center’s tech. support lines involve dome camera problems, however after investigating the situation usually the installation is at fault.
The most common problem is lack of power. Outdoor motorized (24VAC) domes can require in access of 100 watts of power, most installers can’t believe such a small piece of equipment draws so much juice but if you add up the wattage of the heaters, fans, motors, and camera, you will see it totals up quite quickly. Wire gauge is crucial in respect to how many meters the wire runs, as opposed to the equipment’s total power consumption. Numerous times calls have been received stating, »When panning and tilting simultaneously, the camera looses video or gets wavy. » When asked to confirm the gauge and length of the power supply line, the response usually is, « That can’t be the problem, the installation has been fully operational for over a year. » Sure when the equipment is new and the installation is such as to provide only the minimum power requirement, it will work. However the recommended wire gauge and transformer rating will assure you that your installation will keep on working after time as it’s motors and electronics age, and begin to consume greater quantities of power.
The maximum voltage drop (24VAC) should not exceed 10 percent. Your equipment’s manufacturer should specify wire gauge and cable run distances. If you can’t acquire the information, here is a table for your reference.
Outdoor installations also pack another nice little surprise… Condensation.
The dome’s onboard heating system will keep the dome warm and dry under most situations, as long as you assure that all external openings are plugged. Any pipe holding a dome by it’s topside will heat, cool and eventually « sweat » into the dome’s electronics. See the two photos of a dome’s « insides » that had been installed for only less than a year.
Now lets jump back to wires and their effect on your installation. Good quality CCTV grade coaxial cable, used in a typical CCTV application must have an all copper center conductor with a 95 percent copper braid shield. Cables using aluminum foil shielding are designed for transmission of radio type signals, not CCTV. Their use in a CCTV system could possibly degrade the video signal to the extent that you could never achieve proper system operation and your installation will not be able to handle any type of « up the coax. » control. Prior to any cable use, cut the center conductor to confirm it is solid copper all the way through. Copper clad conductors (silver in the center) have much greater loop resistance at base band video frequencies and should be avoided in CCTV installations. As for the gauge of coaxial cable to use, again you must refer to the equipment’s manufacturer for their recommendations.
If you are going to use RS232, RS422 or RS485 to communicate with your dome, again be sure of the cable you plan to purchase. Purchase only cable with the EIA RS232/422/485 rating. Other types of cables are designed for other uses, not dome control. Distance of the cable run can be much greater than your coaxial run, but to assure trouble free operation, wire your domes in a daisy chain configuration and be sure to terminate the last unit. Star configurations can be used provided you install a « hub » type device.
Now for the clean up.
Having contacted the world’s largest CCTV manufacturer and asking about the most common technical inquiry regarding miniature dome cameras, I was surprised to find it is about cleaning the lower dome. Many installers are using household type cleaning products to clean the « bubble ». These little pieces of plastic are optically correct and quite expensive to replace. They are manufactured from many different forms of plastics, so any one cleaner would not be the answer. The equipment manufacturer (again) will be able to inform you of the correct cleaner to use, not to void the warranty and to keep the dome sparkling clean.