Wednesday, October 28, 2009

Tips on fitting CCTV to a house.

The prospect of drilling holes through the external walls of your home to run the power and video cable for a camera may at first seems only feasible for the most accomplished DIYer.
With a little forethought it can be remarkably simple.

Positioning of cameras
Most people want to make the camera position as discreet as possible. The modern bullet-type camera is no bigger than your small finger in length and can easily be located under or on the fascia/soffit boards where the roof line meets the wall. This location also provides good shelter from wind and rain and can be shaded from excessive sunlight. The height of the camera position will give a good area of view and minimise the risk of vandalism.
However, another advantage of this location is cabling. It is usually easy to run the cables into the loft from this position. Many houses have a small ventilation gap between the roof tiles and the external wall, or a small hole may be drilled in the fascia board to gain access to the loft.

It is usually easy to pick up mains power in the loft or at least if additional cabling is required it is now internal. Wireless transmission can be used for the video signal with the receiver being placed next to the monitor or recorder (TV, VCR, PC etc.). That's it, installation complete.
A hard-wired system can almost be as easy to install. Locate the TV aerial down-lead that may be in the loft or run down the outside of the house. It is usually possible to run the CCTV camera video cable alongside the aerial cable, which will lead directly to the TV.
A neat method of connection is to use an RF modulator. This little box changes the camera's video output to an RF output. This means you can pipe the CCTV images down the existing TV aerial down-lead and view on the TV/VCR as if it were another channel. If the house is fitted with a TV aerial distribution system, this method of connection allows the camera pictures to be viewed on all TV sets.

Addition of Switchers etc.
Consider placing switchers, mutiplexers or DVRs in the loft. This contains all the camera cabling in the loft with just one output cable to a monitor. It also hides away the recording device.

Other ideas
Consider positioning the cameras indoors. Point each camera at the exterior doors. Use a motion detector or PC-based system to activate the camera when a door is opened.
The advantage of this type of system is that you do not need a traditional burglar alarm and sensors. The output of the system can be connected to an alarm or, better still, the more sophisticated methods of dialing/SMS to your mobile phone.
This method avoids activation of the motion detector by sudden changes in light levels. Set the activation area just above the level of the cat flap to allow freedom of passage for your pets.

CCTV Monitors or TVs

The signal from a cctv camera is classed as analogue, 1 volt peak to peak into 75 Ohms. A compatible display device must be used to view the images.

The simplest method of displaying the images from the camera is by connecting to the AV input or SCART input on a television set. Most modern TVs now have these type of inputs. The AV input is usually a RCA/Phono type of connector. A simple BNC to Phono converter is all that is required to connect cameras fitted with a BNC type of connector. Most of our camera kits are supplied with BNC and Phono connectors. Alternatively, a BNC to SCART connector can be purchased as an optional extra.
Switchers, multiplexers and digital recorders generally have BNC input connectors.

If you have an older type television that does not have an AV or SCART connector it is possible to convert the camera signal to the broadcast frequency and connect through the aerial input. A small device called an RF Modulator or Wide Band Modulator provides this function.

Alternatively, for more complex or dedicated cctv system a specialist cctv monitor can be used. The tubes or screen (referred to as the CRT)used in cctv monitors are of a much higher resolution than standard TVs. The resolution is measured in TV lines and on monochrome monitors this can be up to 1000TV lines. A good quality TV will be classed at 450 TV lines. These figures are measured at the centre of the tube and will be less at the edges.
Monitors are also designed for continuous running and will contain a high-reliability long-life power supply.
If you are fitting high definition cameras with over 500 TV Lines resolution then a suitable cctv monitor is needed.

LCD screens are now available for cctv applications. The advantages of LCD monitors are:
They are smaller and lighter than CRT monitors
Offer the possibility of 12 volt operation
Offer high resolution that is uniform across the screen
The resolution does not decrease with the age of the monitor as is the case CRTs.
The disadvantage is the cost although this is reducing rapidly.

An LCD monitor designed for connection to a PC does not usually have the required analogue inputs so check carefully before choosing this type of display