April 11, 2023
Power supply monitoring problem, we asked questions together, and many friends in background repeatedly asked, power supply of camera in monitoring system is a prerequisite for ensuring normal and reliable monitoring. equipment, how to intelligently organize power supply of video surveillance system and it is very important to choose right power cord in video surveillance system. In this issue, we will understand application of power supply monitoring.
1. Power setting
The camera's power supply setting depends on whether camera is on side of control unit or at a relatively long distance. It is enough that power of power supply is greater than sum of powers of camera.
If distance is far, AC 220V power supply should be distributed on side of camera, and then an adjustable power supply should be used to convert voltage to supply power to camera. The AC power line and video line must be larger than 30 cm to avoid magnetic field interference and affect image delivery quality.
Second, power supply selection
The choice of power cord is only possible by calculation. Operating current of commonly used camera with 12V power supply:
Regular bolt or hemisphere: Working current is about 200-300mA, you can choose 500mA-1A power supply
Built-in camera: working current is about 350-400mA, you can choose 1A power supply
Small to medium size infrared camera:operating current 600-700mA, 1A power supply can be selected
Large infrared camera:Working current 1000mA-1200mA, 2A power supply can be selected
Power Supply In a monitoring system, a camera can be powered individually or multiple cameras can be shared power. If several chambers are fed centrally, required current is equal to sum of currents of several chambers.
Suppose monitoring system needs 10 dome cameras with a common power supply, because current of one dome camera is 300-400mA, so current of 10 cameras is 3000-4000mA, you should choose 5A or 6A power supply .
Third, choose diameter of power cord
Assuming distance between four cameras and monitoring system is less than 40 meters, each camera can be individually connected with a RVV2×0.5 power cable to monitoring host and powered by a small switch. power unit; if there are 4 hemispheres or bolts, you can also choose two 12V1A power supplies or one 12V2A power supply, and four cameras are connected in parallel to save wires;
If there are many cameras, 8 cameras, a powerful stabilized 12 V DC source should be used for centralized power supply. At this time, due to large current, it is necessary to take into account voltage drop on power line. Generally 8 cameras For camera system, if maximum distance is less than 40 meters, you can use RVV2*0.75 cables for centralized power supply; if 16-channel system is centralized for power supply, RVV2*1.0 power cables should be used. be chosen. The above introduction is to choose power cable within 40 meters from camera to monitoring host.
If distance from camera to host is more than 40 meters, you should consider using a centralized 220V power supply and convert camera side voltage to 12V to power camera. Under normal circumstances, power supply is 220V, if system is not too large, you can choose RVV2*0.75 wire if distance is less than 8 channels and within 200m. If there are more than 8 channels, they are all high voltage. power infrared cameras, you should consider using RVV2 * 1.0 power cord, and if distance is longer, for security betterIt is best to use RVV2*1.5 wire.
Fourth, how to choose power cord
1. Use a twisted-pair power supply
The CCTV camera's power line uses five or more categories of unshielded twisted-pair cable, which simplifies wiring, but must ensure that transmitted power can meet requirements of equipment. For example, operating power of equipment is 10-12VDC, current is 500mA, and internal resistance of twisted pair is 10Ω/100m (the actual use of oxygen-free copper for 100m measurement is 9.53Ω). if transmitted power is 12 VDC, taking into account voltage attenuation over distance. To ensure normal use of equipment, transmission power is within 150 meters.
2. Autonomous power supply from RVV network
Depending on power of terminal camera, power of a normal fixed bolt is less than 10W, an infrared bolt is usually less than 20W, and a dome camera is about 35W. In terms of power, RVV2*0.5 line is sufficient, and national standard 0.5 line can carry about 1KW load.
At long distances, considering attenuation, it is recommended to use a line of at least 1.0. If number of cameras is small (within 5) and distance between cameras and surveillance host is relatively close (less than 50 meters), each camera can be independently brought into surveillance room with a PBB2×0.5 power cable and powered with a small transformer.
If number of chambers is large, a large regulated 12V DC power supply should be used for centralized power supply. During construction process, total power of all chambers and voltage drop caused by transmission line (so-called "line loss", resistance of copper wire with specification 1 m2 per 100 m is 1.8 ohm). For building monitoring, two 2.5-6m2 copper double plastic wires are commonly used as main power line during construction to lead from observation room to line well and run along line well to line wells on each chamber floor. For power supply of each camera on floor, you can use one power line RVV2x1 or RVV2x1.5 (if number of cameras on this floor exceeds 6) to power cameras, or wires in sheath RVV2x0.5 can be used to bring them one by one. Appropriate power supply.
Fifth, how to connect long distance power
Of course, at more than 500 meters, when we use a line, we must estimate its pressure drop approximately, in order to decide which line to use, there is an automatic calculation formula.
Automatic differential pressure formula (download)
Extraction code: Crak
Interested friends can download it.
So how do you power up surveillance over 2 kilometers away?
In this case, solar energy can be used for power supply. We mentioned solar power solution some time ago, and you can find it in history.