Car monitoring manufacturers revealed four questions
by：Eagle Mobile Video2020-05-20
Car DVR is not a new product of the times in the security industry, but the technical content, I am afraid that only those who have actually done car DVRs can realize it.
First, what is the difference between a car hard disk recorder and an ordinary hard disk recorder?
Ordinary hard disk recorders use 220V alternating current, and the stability of voltage and current is relatively stable. Furthermore, because the location environment of ordinary hard disk recorders is fixed, there is almost no relative vibration opportunity, so the earthquake resistance of ordinary hard disk recorders can be ignored. But the car DVR is different. First of all, the voltage and current on the car can not be understood according to conventional ideas. The voltage on the car is 12 / 24V, but in fact, the 12V car ca n’t do 12V voltage regulation, the same is true for 24V, so the design of the power board Very important, the design of the power board must consider many aspects.
Car video recorder
Second, how to design the power supply of car hard disk recorder?
If you want to ensure the normal operation of the car hard disk recorder, you must first 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 only one adapter is needed for the power supply of ordinary hard disk recorders. An adapter is nothing more than a transformer. A filter circuit, a little conscience plus a protection circuit, no conscience protection circuit is not installed, it is cheap, so the cost of ordinary hard disk recorders and maintenance costs are relatively low.
But for car hard disk recorders, the first thing to do is to narrow and thin the dynamic voltage and current. How to ensure the normal operation of the car DVR, stable voltage and current is very important, but on the other hand, the input power of the device is fixed, as can be seen from W = U * I, the current also changes when the voltage changes. The direction of current change is always opposite. So if the starting voltage is lower, the relative starting current will increase. Macro is so simple, but it can do this function stably and ensure the normal operation of the equipment, then it takes a lot of effort. The first thing is the design of the protection circuit. You need to know that the power board of the car hard disk recorder should be within 1 hour. Withstand hundreds of impacts, the protection circuit is not doing well, at least the power board is damaged, and in the worst case, it directly penetrates the power board and burns the motherboard.
Third, how is the anti-shock design of the car hard disk recorder?
The anti-seismic design of the car DVR is very important. To put it plainly, it is actually how to protect the hard disk. Because the current hard drives are mechanical spindle hard drives, the distance between the read and write head and the disk surface is only a few microns. If you look at it with your naked eyes, the read and write head is attached to the disk surface, but even if you do n’t understand the hard disk, you should understand that The rotating hard disk should rotate at least 90 times per second. If the read-write head is attached to it, it will not be worn out in a long time. At such a short distance, if the earthquake resistance is not good, as long as the read / write head has a little bit of vibration, the hard drive will have bad sectors, and the read / write head will crash (hard drive terminology). So hardware shock resistance is very important.
Fourth, how is the hard disk fault-tolerant error correction of the car DVR designed?
Answer: The hard disk's fault tolerance and error correction capability is a difficult problem that it has been trying to solve in the IT hardware industry and the software industry since the hard disk has been available. For an embedded system, it is difficult to achieve a perfect fault-tolerant and error-correcting design! But for the design of the embedded system, the embedded system is originally designed to pursue better stability and execution speed Design, but there is a problem that can not be ignored is poor portability, resulting in once the design can not be changed too much. So its first design idea is very important. The current effective method for hard disk fault tolerance and error correction in embedded systems is read and write control.