Vehicle-mounted video recorder is not a new product of the new era, but the skill content, I am afraid that only those who have actually done the vehicle-mounted video recorder can grasp it.
1. What are the differences between VHDR and VHDR?
The general hard disk video recorders use 220V alternating current, the voltage and current stability is relatively stable, and then because the general hard disk video recorders have a fixed azimuth environment and almost no relative oscillation time, the anti-seismic function of the general hard disk video recorders can be neglected. But car-mounted hard disk recorders are different. First of all, the voltage and current on the car can not be understood according to the conventional way of thinking. The voltage on the car is 12/24V, but in fact, the 12V car can not achieve 12V voltage regulation, 24V is the same, so the planning of the power board is very important. The planning of the power board should take into account many aspects.
2. How to plan the power supply of VHDR?
In order to ensure the normal operation of the VCR, the first thing is to ensure that the output power of the power board is stable.
In a fixed narrow voltage environment, because the input voltage and current are basically stable, and in terms of electricity, the output power determines the input power, so in general, only one adapter is needed for the power supply of hard disk recorders. An adapter is nothing more than a transformer plus a filter circuit, a little conscience plus a maintenance circuit, and no conscience maintenance circuit is installed. Cheap, so the cost of general hard disk video recorders and maintenance costs are relatively low.
However, the first thing to do about VHDR is to narrow and refine the dynamic voltage and current. On the other hand, the input power of the equipment is fixed. It can be seen from W=U*I that the current changes when the voltage changes, and the direction of the change of voltage and current is always opposite. So if the starting voltage is lower, the relative starting current should be added. Microscopically, it is so simple, but to achieve this function safely and ensure the normal operation of the equipment, it will take a lot of effort. The first battle is to plan the maintenance circuit. We should know that the power board of the car-mounted hard disk video recorder has to withstand hundreds of shocks in an hour, and the maintenance circuit is not well done. If the power board is damaged, the main board will be burned down directly.
3. How to plan the earthquake resistance of vehicle-mounted hard disk video recorders?
Seismic planning of VHDR is very important. To tell you the truth is how to maintain the hard disk. Because today's hard disks are all mechanical spindle hard disks, the distance between the read-write head and the disk surface is only a few microns. If you look at it with the naked eye, the read-write head is attached to the disk surface, but even if you don't understand the hard disk, you should understand that the 5400-turn hard disk should scroll at least 90 times per second. If the read-write head is attached to it, it will not be long before the read-write head is worn out. At such close intervals, if the seismic performance is not good enough, only a little tremor in the read-write head, a slight bad way in the hard disk, and a crash in the read-write head (hard disk terminology) are needed. So the hardware anti-seismic is very important.
4. How to plan the error tolerance and correction of the hard disk of VHDR?
Answer: Fault-tolerant and error-correcting ability of hard disk is a difficult problem that the IT hardware profession and the software profession always strive to deal with after having hard disk. For an embedded system, it is very difficult to achieve a perfect fault-tolerant and error-correcting plan. However, as far as the planning of embedded system is concerned, the original purpose of embedded system planning is to seek better stability and execution speed, but one problem that can not be ignored is poor portability, which results in that once the planning can not be changed too much. So its initial planning idea is very important. Embedded system on the hard disk error-tolerant correction, now a useful way is to read and write control ability.
Page 2: Selection Specification for Vehicle-mounted Hard Disk Video Recorders
Specification for Selection and Purchase of Vehicle-mounted Hard Disk Video Recorders
Although the embedded system is the same as the general DVR, the vehicle DVR skills are more chaotic than the general DVR, and the key points of demand processing are also different. Therefore, they are two completely different concepts. Vehicle-mounted DVR is used in mobile vehicles. Because of the different vehicle and road conditions, it has a great impact on hard disk reading and writing data, and has a great damage to the equipment. As a result, the anti-seismic skills have become the fundamental requirement for vehicle-mounted DVR. At present, there are mainly measures to reduce the vibration of the whole machine, the hard disk shelf and the hard disk.
In the security profession, the car-mounted DVR shopping mall is still chaotic, and the user's awareness is not deep. Therefore, it is often found that the general DVR is used to fake the car-mounted DVR. Therefore, the actual effect needs to be investigated by oneself.
2. Voltage stabilized power supply
Voltage stability is another important skill of vehicle DVR. Because in the internal driving process, the vehicle will burn, brake, step on the throttle and other actions, these actions will make the output voltage of the vehicle oscillate in different magnitudes, and it is very simple to form the burnout of the vehicle DVR. Therefore, a wide voltage input is necessary for a vehicle-mounted DVR to adapt to this voltage change. Nowadays, 6-36V wide voltage is generally chosen to satisfy the needs of mobile vehicles.
We should also pay attention to the fact that if the car suddenly goes out when it bumps and the power supply is cut off, the on-board DVR should have the function of active maintenance of the power supply to ensure that the data in the hard disk will not be lost.
3. Heat dissipation
Because of the influence of environment and climate, the temperature difference of vehicles changes greatly in the course of operation.
This puts forward high requirements for the heat dissipation function of vehicle-mounted DVR. Therefore, if the heat dissipation function is not good, the life of the product will decline, together with the monitoring effect will be affected. Now, some products are heat dissipation through fans, and some are heat dissipation through fuselage. So when choosing to buy, Fang Hao first runs for a period of time, then measures the fuselage temperature, and watches the actual effect of the picture.
IV. Picture Clarity
The clarity of the picture directly affects the monitoring effect, so when purchasing the product, it depends on which processing chip the product chooses, which compression pattern, and what resolution it supports. Now the product support is generally CIF to D1, choose D1 video, CIF transmission. To investigate the actual effect, we need to record a video at different resolutions, investigate the effect of video playback, whether the picture is clear, whether there is delay.
Fifth, interface firmness
In the car, because of braking, acceleration, fluctuations in distance, the sensation is greater. If the interface is not strong, the wiring may drop at any time, resulting in picture tremor, video loss, power loss. Therefore, when purchasing products, we should carefully investigate whether the interface is strong. I have seen in the test process, some manufacturers will assemble most of the interface on the back board, replaced by a multi-needle interface, bundled all the data lines into a bunch, which has played a very good effect on the interface firmness. [nextpage]
6. Wireless transmission
In addition to providing local video and forensic materials, vehicle DVR also needs to send the obtained video information back to the control center in time to facilitate the control center to timely understand the vehicle situation and assembly management. Therefore, wireless transmission is particularly important.
At present, mobile GPRS and Unicom's CDMA network are mainly used, but because of the bandwidth and cost problems, real-time transmission can not be achieved. Only 5-7 frames of CIF frame can be transmitted in one second. Therefore, the user can check whether the transmitted pictures are clearly circulated in the control center.
Vehicles are usually cleaned every day, especially on buses. After the bus arrives at the station, the operators will use water to wash the carriage. If the waterproofing function is not good, the water droplets may enter the cabinet. When the vehicle burns and starts, the equipment may be burned out. Therefore, the waterproofing function of the vehicle DVR can not be ignored.