Automobile instrument
Introduce
The instruments on the dashboard of different cars are different, but the conventional instruments of general cars include speedometer, tachometer, oil pressure gauge, water temperature gauge, fuel gauge, charging meter, etc. In modern cars, automotive instruments also need to be equipped with voltage stabilizer, which is specially used to stabilize the instrument power supply voltage, suppress the fluctuation amplitude and ensure the accuracy of automotive instruments. In addition, most instrument displays are based on sensors. The sensing device changes its resistance value according to the state change of the monitored object, which is represented by the instrument. The most conspicuous thing on the dashboard is the speedometer, which represents the speed of the car in kilometers per hour (km/h). The speedometer actually consists of two instruments, one is the speedometer and the other is the odometer.
The vehicle instrument is composed of various instruments and indicators, especially the driver's warning light, which provides the driver with the required vehicle operation parameter information. According to the different working principles of automobile instruments, they can be roughly divided into three generations. The first generation of automobile instrument is mechanical motion meter; The second generation of automotive instruments is called electrical instruments; The third generation is full digital automotive instrument, which is a networked intelligent instrument with more powerful functions, richer display content and simpler wiring harness links.
Most automotive instruments are the third generation instruments, which can drive the pointer of the basic instrument through a stepper motor, or directly display graphic or text information using LCD. At the same time, it also has an intelligent processing unit that can interact with other control units of the vehicle.
The function of the automobile instrument is to obtain the required data and display it in an appropriate way. Previously, the instrument was usually limited to 3-4 quantity displays and 4-5 warning functions. Now, the new instrument has about 15 quantity displays and about 40 warning monitoring functions. Different information can be obtained and displayed in different ways. At present, there are three main ways to obtain the information of the new instrument: transmission through the body bus; Through A/D sampling conversion; Obtained through IO status change.
There are five main display modes:
1.Drive the pointer to rotate by driving the stepping motor;
2.Display graphic or digital information through dot matrix LCD screen;
3.Display through segmented LCD screen or digital tube;
4.Display through LED switch;
5.The current status is indicated by different beeps of the buzzer.
According to the above requirements, the vehicle instrument panel designed in this paper is composed of MCU system, LED display driven by stepper motor, LCD display, alarm function, memory function, key processing, LIN bus communication, low-speed fault-tolerant CAN bus communication and power supply.
