dethdeks
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How to Design your own Security Camera System - 2008/08/25 03:34
So you have decided to build a video Security (observation) system yourself. This is not that difficult of a task but you have to know few very important simple things before you start.
Let’s start with cameras. You have to decide on how many you need now, and how many you might need in the future. If you think you will be fine with just three for now, but maybe later you will add few more, remember to get DVR that will let you expand your system in the future. Some offer 4ch or 16ch DVR. 4 may be enough for small store or office, but for everything else you will need more than that. Let’s take a convenience store as an example. You will need one camera facing cash register, one at entrance door, and this leaves you just 2 cameras left for the rest of the store. Probably this won’t be enough.
So always count the cameras before you buy DVR. Good practice is to leave always some empty channels on your DVR. 90% of customers usually call back within one year after installing system, and ask for additional cameras. Keep it in mind designing your system.
When you know how many cameras you will need, now it’s time to decide on kind and performance of each one.
So we have outdoor/indoor, day & night, infrared, daytime, hidden, spy, professional, wireless.
Deciding if you need outdoor or indoor is easy. Remember only that with severe indoor conditions it may be better to use weatherproof (weather resistant) camera were there is dust,
moisture, and extreme variations in temperature).
If you have night-lights around your property, you can use day & night cameras. Infrared are usually use in completely dark spots. Remember also, that LED’s on infrared cameras light up at nighttime. You can easily see camera. It’s not as bright as flashlight, but you can see dark red light of LED’s when you look at the camera.
If you don’t want your cameras to attract too much attention, use small bullet or dome cameras. But if you own for example car dealership, you want bad guys to know that you have surveillance. This is when you put professional cameras in outdoor enclosures. They will think twice before entering property. Plus c-mount cameras are state of the art products. They use the most advanced digital picture processing. Auto iris, back light compensation, auto gain control, white balance are just some of the features you can find in c-mount cameras. It's also easy to use different lenses from wide 3.5mm to telephoto 100mm.
Every security professional will tell you, that it’s always better to go with hard wired cameras than wireless. And it’s not only about the cost. Wireless systems are much less dependable. They trigger a lot of false alarms. On the top of that anybody can buy RF scanner and simply tap into your surveillance system. And you don’t want that to happen.
Since you already know what you are looking for, I should mention few more things. Pay good attention, when buying cameras. For example most of professional cameras do not come with lens. You have to purchase them separately. Each camera needs power supply unless you using multi-channel power distributing box. You can make your life easy and use plug & play cables. They good for short runs (up to 300ft). If you need longer runs, use coaxial RG59 cable and low voltage cable for power. In this case you will need to put that ends on power cable and crimps on coax. This requires extra tools. You can also instead of using coax and low voltage cable, use Siamese cable. It may be a little more expensive, but makes running cables so much easier. When buying PTZ camera remember to get PTZ controller or RS232 adaptor. These do not usually come with camera.
Manufacturers use usually few values to describe camera. The most important are:
1. resolution (380 TV lines is a standard, ultra high starts from 480 TVL)
2. LUX rating, amount of light needed for camera to work properly. 1 LUX equals light produced by one candle. Today’s cameras are rated usually below 1 LUX. 0.01 LUX means basically Day & Night camera, Infrared Cameras need no light at all since they are produce infrared beam, so they rated 0.0 LUX.
3. Lens. Usually surveillance cameras use wide lenses 2.5mm and up. Very popular 3.6mm lens would give you about 70 degrees field of view (FOV) horizontally and 57 degrees vertically. 6mm lens would give you about 48 degrees FOV horizontally and 37 degrees FOV vertically (for 1/3” CCD sensor). More mm means smaller FOV. Telephoto lenses are 20mm and up.
4. CCD sensor size (usually ¼” or 1/3”). The smaller the size, the smaller FOV. Simply 1/3” CCD sensor see more with same lens than ¼” CCD sensor.
There are few other values like backlight compensation, auto iris, auto white balance etc. There are many cameras on the market. Even if technical specs are same, you can see the difference comparing them side-by-side. We make sure all our cameras are the highest quality. We test weekly tens of cameras and usually only few of them qualify to be offered to our customers.
Now let’s focus on DVR unit. Today nobody uses VCR’s anymore. All modern CCTV systems are based on DVR. DVR is a time-lapse video recording device, multi-channel multiplexer and web server. All in one. All our DVR units have following features:
1. Multi channel capability (can support many cameras)
2. Triplex function (record, playback and remote access, all can be done at the same time)
3. Recycle function (it overwrites oldest data with the newest keeping always last few weeks of video)
4. Motion activated recording (it records only when motion is detected and only from camera(s) that are detecting motion at that time)
5. Recording on schedule (weekly schedule of recording for each camera can be set)
6. Remote playback, viewer and control (DVR can be control and live picture can bee seen over the internet)
7. Video backup (if you need to save some of the video)
Most important values used by manufacturers:
1. Number of channels (maximum number of cameras that can be plugged in to the DVR)
2. Maximum FPS (frames per second) DVR can record. It is total number for all channels. It can be different for recording and for display. Let’s say 4 CH DVR 120 FPS recording/display. This means 4 camera DVR can display and record with rate of 120 FPS. If you divide 120FPS by 4 cameras you will get 30FPS. So each camera can display 30FPS and can record 30FPS (30FPS is also known as “Real Time”). But lets take 4CH 30FPS DVR. If you use only one camera you can get maximum real time recording and display. If you use all 4 cameras it will give you 7.5 FPS for each camera. But remember, you can change it; you can set one camera for example to record with 15FPS and the rest of the cameras to record with 5FPS. The total number of frames multiplied by number of cameras cannot exceed maximum FPS for particular DVR. 98% of surveillance DVR do not record with more than 3-5FPS. There is no reason to record video with higher FPS rate. It also saves you a lot of space. Remember, real time recording consumes a lot of memory. It’s not practical. So if you let’s say getting 16CH DVR and you will actually use all 16CH, 120FPS will be enough in most cases. This will give you 7.5 FPS for each camera which is more than enough even for watching your cash register. Real time recording is used only in extreme situations (very fast moving objects, casinos (card tables)).
3. Storage space in GB (standalone and PC based DVR’s usually come with hard drive built in, but you can always add extra one. DVR boards use hard drive of your computer, good practice is to have separate hard drive just for DVR). DVR boards work fine with 95% of today’s computers. Sometimes graphic card upgrade is required. They also do not need dedicated PC. You can simply let the system run in the background. You will not even notice the difference in performance of your PC. Of course having dedicated PC is recommended especially for large systems. We prefer PC based DVR’s. Simply because they are more user friendly, software updates are available, have more features and can be easily customized. But if you don’t want to have another PC you can always use simple standalone DVR’s. They are usually very dependable and have all basic features to run your surveillance system.
REMEMBER: The basic CCTV system includes:
1. Cameras
2. DVR unit
3. Cables (one for each camera when using Plug&Play cables, or coaxial RG59 and low voltage 22/2 (or Siamese) when you have really long runs 300ft and more)
4. Power supply (one for each camera when using single power adaptors, or multi-channel power distribution box)
5. Monitor (regular TV when using standalone DVR, PC monitor when using PC based systems)
Optional - Internet router and Internet access (when you want to be able to access your system via internet)
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