How to choose monitoring system power and power cord?

The power supply of the camera in the video surveillance system is the power supply to ensure the normal and reliable operation of the monitoring equipment. How to properly arrange the power supply of the monitoring system and select the power line is very important in the video surveillance system.

First, the power settings

The power setting of the camera is based on whether the camera is on the side of the control host or a relatively long distance. If it is relatively close, install a high-power DC stabilized power supply directly next to the host, and connect multiple cameras to this power supply. It is more than the sum of the power of the camera.

If the distance is far away, 220V AC power should be distributed to the camera side and then converted to power supply by the regulated power supply. The distance between the 220V AC power line and the video line should be greater than 30 cm to avoid magnetic field interference and affect the image transmission quality.

Second, the choice of power cord

The power line selection must be calculated to obtain a reasonable selection. The working current of the commonly used 12V power supply camera:

Ordinary gun or hemisphere: the working current is about 200~300mA, you can choose 500MA-1A power supply;

Integrated camera: The working current is about 350~400mA, and the power supply of 1A can be selected.

Small medium-sized infrared camera: the working current is 600-700MA, you can choose 1A power supply;

Large infrared camera: working current 1000MA-1200MA can choose 2A power supply;

Power supply In a monitoring system: the camera can be powered separately or in multiple centralized powers. If multiple cameras are powered centrally, the required current is the sum of multiple camera currents.

Suppose a monitoring system requires 10 dome cameras to share a common power supply. Because the current of one hemisphere is 300-400MA, the current of 10 cameras is 3000MA-4000MA, so you should choose 5A or 6A power supply.

Third, the choice of power cord diameter

Assume that the four cameras have a monitoring distance of less than 40 meters. Each camera can be individually wired with RVV2×0.5 power supply to the monitoring host and powered by a small switching power supply. If four hemispheres or a gun, you can also select two 12V1A power supplies or one. 12V2A power supply, 4 cameras adopt parallel connection to take power, which saves wire; if there are more cameras, 8 cameras, it should be powered by high-power 12V DC regulated power supply. At this time, because the current is too large, it must be Consider the voltage drop on the power line. Under normal circumstances, the system of 8 cameras, the farthest distance is less than 40 meters, can be used for centralized power supply of RVV2*0.75; if the system of 16 channels is concentrated, RVV2* should be selected. 1.0 power cord. The above description is the choice of the power cable from the camera to the monitoring host no more than 40 meters.

If the distance from the camera to the host is more than 40 meters, it is necessary to consider using 220V centralized power supply, and transforming the camera to 12V to supply power to the camera. Under normal circumstances, 220V power supply, as long as the system is not too large, 8 channels or less, within 200 meters, you can choose RVV2 * 0.5 wire, if more than 8 channels, are high-power infrared cameras, you should consider using RVV2 * The power cord of 0.75 is powered. In addition, if the distance is farther, in order to ensure safety, use RVV2*1.0 wire as much as possible.

Fourth, the power cord selection method

1, using twisted pair power supply

Five or more types of unshielded twisted-pair cable can be used as the power supply cable for the surveillance camera to simplify wiring, but you must ensure that the power supply passed meets the requirements of the device. If the working power of the equipment is 10-12VDC, the current is 500MA, and the internal resistance of the twisted pair is 10Ω/100m (measured for actual use). If the power supply is 12VDC, considering the distance voltage attenuation, ensure that the equipment is used normally. The transmission power is within 150 meters.

2, independent RVV line power supply

According to the power of the terminal camera, the power of the general fixed gun machine does not exceed 10W, the infrared gun machine generally does not exceed 20W, and the ball machine is about 35W. From the power point of view, the RVV2*0.5 line is sufficient, and the national standard 0.5 line can carry a load of about 1KW. For long distances, it is recommended to use a line of not less than 1.0 in consideration of attenuation. If the number of cameras is small (less than 5) and the camera is close to the monitoring host (less than 50 meters), each camera can be independently RVV2 × 0.5 power cable to the monitoring room and powered by a small transformer.

If the number of cameras is large, you should adopt a high-power 12V DC regulated power supply for centralized power supply. In the process of work, the total power of the camera and the voltage drop formed by the transmission line (referred to as "line loss"), the resistance of the copper wire of the specification of 1 m2 per 100 m is 1.8 Ω. For the monitoring of a building, two 2.5-6m2 copper-core double-plastic lines are generally used as the main line of the power supply from the monitoring room to the line well, and along the line well to the line well of each camera floor. For the power supply of each camera on the floor, one RVV2×1 or RVV2×1.5 (if the number of cameras in this layer exceeds 6) can be used to supply power to the camera, or use RVV2×0.5 sheathed wire. Corresponding to power supply.

Resistance calculation formula: R=p*L/sp is the unit of resistivity in meters ohm, L unit meters, s unit square meters. The resistance of the copper wire of the specification of 1 m2 per 100 m is 1.75 Ω R = 0.0175 × 100/1 = 1.75 Ω.