What Is a Business Dashboard?

Instrument panel An assembly that installs various indicating instruments and ignition switches in the cab. It is mounted on the instrument panel or as an accessory on the steering column. The dashboard assembly looks like a window, which reflects the operating status of the machine inside the car at any time. At the same time, it is the control center and decorated object of some equipment, and it is the most eye-catching part in the cab. The instrument panel assembly has both technical and artistic functions, and is one of the representative of the vehicle style.

Chinese name: Dashboard
Foreign name: instrument panel

composition: Various instruments, indicators, warning lights, etc.
category: Odometer, tachometer, oil pressure gauge, etc.
display: Mechanical, LCD screen

Dashboard introduction

Automobile meters are composed of various meters and indicators, especially warning light alarms for drivers, etc., to provide drivers with the required vehicle operating parameter information. According to the working principle of automobile meters, it can be roughly divided into three generations. The first generation of automotive meters is a mechanical movement watch; the second generation of automotive meters is called electrical meters; the third generation of all-digital automotive meters, he is a networked, intelligent instrument, which is more powerful and displays Richer and simpler harness linking.

Automobile meters are mostly third-generation meters. It can drive the pointer of the base table by stepping motors, and can also use the LCD screen to display graphics or text information directly. At the same time, he also has an intelligent processing unit, which can interact with other car control units.

The function of the car instrument is to obtain the required data and display it in a suitable way. The previous instruments were generally limited to 3 to 4 quantity displays and 4 to 5 warning functions. Now the new meters have about 15 quantity displays and about 40 warning monitoring functions. Different information is obtained by different acquisition methods and display methods. At present, there are three main types of new instrument information acquisition methods: transmission through the body bus; conversion through A / D sampling; and acquisition through IO status changes.

There are five main display methods:

1. Drive the governing rotation by driving the stepper motor;

2. Display graphic or digital information through dot matrix LCD display;

3. Display via segment LCD screen or digital tube;

4, through the switch display of LED lights;

5. The current state is indicated by different beeps of the buzzer.

According to the above requirements, the points of the automobile instrument panel designed in this article are MCU system, stepper motor driven LED display, LCD display, alarm function, memory function, key processing, LIN bus communication, low-speed fault-tolerant CAN bus communication, and power supply. All aspects constitute. ^[1]

Dashboard principle

Dashboard speedometer

The traditional speedometer is mechanical. A typical mechanical odometer is connected to a flexible shaft. There is a steel cable in the flexible shaft. The other end of the flexible shaft is connected to a gear of the transmission. The rotation of the gear drives the rotation of the steel cable. Drive a magnet in the odometer cover ring to rotate, the cover ring is connected to the pointer and the pointer is set to the zero position by the hairspring. The speed of the magnet's rotation speed causes the size of the magnetic field lines to change, and the pointer is driven because the balance is broken. This speedometer is simple and practical, and is widely used in large and small cars. However, with the development of electronic technology, many car meters have used electronic speedometers. A common one is to obtain a signal from a speed sensor on the transmission and deflect the pointer or display the number through the change in pulse frequency.

Dashboard Odometer

The odometer is a digital meter that engages the worm on the speedometer drive shaft through the transmission gear of the counter drum to make the counter drum rotate. The characteristic is that the upper drum rotates a full circle and the lower drum rotates. 1/10 laps. Like the speedometer, the odometer also has an electronic odometer, which obtains the odometer signal from the speed sensor. The mileage numbers accumulated by the electronic odometer are stored in non-volatile memory, and the state data can be saved even in the absence of electricity.

Dashboard tachometer

Another more prominent instrument is the tachometer. In domestic cars, the tachometer was generally not set before, but in recent decades, various types of cars have been installed with tachometers, and some manufacturers have also used it as a configuration content of automobile grades. The unit of the tachometer is 1 / min × 1000, which shows how many thousand revolutions the engine rotates per minute. The tachometer can intuitively display the engine's speed under various operating conditions. The driver can know the engine's running status at any time, and cooperate with the transmission gear position and throttle position to maintain the best working condition. benefit.

The tachometer is generally set in the dashboard and placed symmetrically with the speedometer. The tachometer works according to the magnetic principle, it receives the pulse signal generated when the primary current in the ignition coil is interrupted, and converts this signal into a displayable speed value. The faster the engine speed, the more pulses generated by the ignition coil, the greater the speed value displayed on the table.

Cars are generally electronic tachometers, with pointer type and LCD digital display type. There are digital integrated circuits in the table. It calculates the voltage pulse sent by the ignition coil to drive the pointer to move or digital display. In addition, there is a tachometer that displays the tachometer value after taking out the pulse signal from the generator and sending it to the tachometer circuit for interpretation. However, due to factors such as the generator belt slipping, the value is not accurate. ^[2]

Dashboard composition

The oil pressure gauge, water temperature gauge and fuel gauge on the instrument panel are all directly related to the engine's work. Each of them has a corresponding sensor to reflect the information of the monitored object on the instrument.

Dashboard oil pressure gauge

The oil pressure gauge is a meter that displays the oil pressure, and the unit is kPa (kPa). The oil pressure gauge sensor is a piezoresistive sensor, which is fixedly connected to the engine oil pipeline with threads. The pressure of the oil pushes the contact piece to move on the resistance, so that the resistance value changes, which affects the amount of current passing through the instrument to ground, and drives the pointer to swing. Because the oil pressure has a certain pressure range, for clarity, many cars' oil pressure gauges are indicated by indicator lights. If the engine is still on when the engine is running, it means that the engine lubrication system may be abnormal.

Dashboard water temperature gauge

The water temperature meter is a meter showing the temperature of the cooling water, and the unit is ° C (Celsius). Its sensor is a thermistor-type sensor that is screwed to the engine cooling water channel. The thermistor determines the amount of current flowing through the coil of the water temperature meter, which drives the pointer of the meter to swing. In the past, the cooling water of automobile engines was used as the tap water. Many automobile engine cooling systems used special coolants, so they were also called coolant temperature meters.

Dashboard Fuel Gauge

The fuel gauge is a meter that displays the amount of fuel in the fuel tank. The unit is L (liter). The pointer points to "F", indicating full fuel, and points to "E", indicating no fuel. Indicates full, half tank, and no oil. There are two coils in the fuel gauge, which are on the "F" and "E" sides. The sensor is a variable resistance controlled by the height of the float. The change in resistance determines the strength of the magnetic field lines of the two coils, which also determines the pointer. Deflection direction.

Dashboard water temperature and fuel gauge

The water temperature gauge and fuel gauge are also indicated by indicator lights. The water temperature indicator lights up to indicate that the water temperature is too high, and the fuel light indicator lights up to indicate that the fuel has reached a low point, as a supplementary reminder.

Dashboard Charging Meter

The charging meter shows the state of charge and discharge between the generator and the battery. There are ammeters and voltmeters. Most of the previous cars used an ammeter. It had a permanent magnet to keep the pointer fixed on the fulcrum in the middle position. A coil surrounds the fulcrum. When a current passes through the coil, a magnetic field is induced. The pointer swings left and right under the action of the magnetic field. The swing direction is determined by the direction in which the current flows through the coil. Therefore, the ammeter is connected in series between the battery and the generator. When the generator charges the battery, the meter displays a positive (+) pole. If the battery discharges to the load more than the generator's charge, it displays a negative (-) pole. Because the ammeter terminals are relatively large and not safe, when the engine is running, the grounding line of the charging lamp is connected and the charging lamp is on; when the engine is not running, the grounding line of the charging lamp is disconnected and the charging lamp is off; if the charging lamp is off When it is still on, the charging system is faulty.

Dashboard alarm

Speedometer and alarm device

The speedometer is composed of a speedometer indicating the speed of the car and an odometer that records the distance traveled by the car. The two are housed in a common housing and driven by the same shaft.

The speedometer uses the mutual induction of magnetoelectricity to make the swing angle of the pointer on the dial proportional to the speed of the car. A dial with graduations is mounted on the case.

The odometer is composed of several counting drums and its rotating device. For ease of use, some speedometers are equipped with both a total odometer and a one-way odometer. The total odometer is used to record the cumulative mileage of the car, and the one-way odometer is used to record the one-way mileage. The one-way odometer can be reset to zero at any time.

The speed alarm device is a speed sound alarm system installed in the speedometer in order to ensure driving safety. If the car's running speed reaches or exceeds a certain speed limit (for example, 100km / h), the speed switch in the speedometer turns on the buzzer circuit and issues an audible alarm.

Oil pressure gauge and low pressure alarm

The oil pressure gauge is a meter that indicates the oil pressure in the main oil passage of the engine lubrication system when the engine is operating. It includes an oil pressure indicator and an oil pressure sensor.

The oil low pressure alarm device sends an alarm signal to the driver when the oil pressure in the main oil passage of the engine lubrication system is lower than the normal value. The oil low pressure alarm device is composed of an oil low pressure alarm lamp installed on the instrument panel and an oil pressure sensor installed on the main oil passage of the engine.

Fuel gauge and low oil level alarm

The fuel gauge is used to indicate the amount of fuel stored in the car's fuel tank. The fuel gauge consists of a fuel level indicator with a voltage regulator and a fuel level sensor.

The function of the low fuel level alarm device is to illuminate the alarm immediately when the amount of fuel in the fuel tank is less than a certain value to draw the driver's attention.

Water temperature meter and water temperature alarm light

The function of the water temperature indicator is to indicate the working temperature of the coolant in the water jacket of the engine cylinder head.

The water temperature warning light can be illuminated when the temperature of the coolant rises to near the boiling point (for example, 95 to 98 ° C) to attract the driver's attention.

The common electrical instruments of automobiles are ammeter, fuel gauge, water temperature gauge and oil pressure gauge. Its role is to test and indicate the performance and status of the relevant parts, and provide a basis and guidelines for the correct use and maintenance of the engine. In order to ensure that the meters can work normally and accurately indicate the performance and status of the relevant parts, they must be used correctly and maintained in a timely manner. ^[3]

Dashboard use note

Dashboard engine water temperature gauge

Engine water temperature gauge is a device that monitors the operating temperature of the engine. Observing the water temperature gauge while driving a car is the most basic knowledge of driving.

With good engine performance. Indication law of water temperature meter:

(1) Just after starting the engine water temperature gauge, it starts to move. But the pointer is generally below 40 degrees. When the engine is running for about 1 minute, the hands start to move slowly upwards. (Of course, the time for the hands to start moving up is different depending on the external ambient temperature. The lower the weather temperature, the longer it takes for the hands to start moving)

(2) When the pointer is moved to 60 degrees, the speed of the pointer movement is obviously slowed down, and even remains at this position.

(3) At this time, the car starts and generally travels 3-4 kilometers. The engine water temperature pointer gradually rises to 80-90 degrees, and it is stable (most of the vehicle water temperature meters have no specific scale, and the general pointer is in the middle of the dial on the table, which is about 80 degrees) Increased and extended driving time. After about half an hour the hands of the water temperature meter will move slightly upwards. However, when the vehicle speed is stable, the water temperature indicator pointer remains stable.

(4) When the traffic light is encountered, the temperature is high outside. You will notice that the pointer starts to rise. You can even hear the cooling fan at the front of the engine start to work.

Abnormal phenomenon:

(1) After the engine is started, the water temperature does not come up, that is, it takes a long time to rise to 40 degrees. And the water temperature indicator pointer is always at 60-70 degrees or 1/4 scale during driving. Generally more pronounced in winter. In this case, the operating performance of the engine thermostat is generally reduced. In this case, the car may experience underpower and fuel consumption. However, the engine is generally not damaged.

(2) The water temperature of the engine rises quickly, and the water temperature reaches the red line position close to the scale after driving for about 10 kilometers. In this case, the engine is operating at high temperatures. Dangerous to the engine. If the water temperature works above the red line, the engine may be scrapped in about 10 minutes. Therefore, when the engine water temperature is too high, it is strictly forbidden to continue to drive, the vehicle must be stopped, the cause must be identified, and the fault must be eliminated before driving.

Dashboard engine tachometer

The table reflects the speed of the engine.

Normal display: When the vehicle is just started, the general tachometer indicates the speed is 1500-1700 rpm.

After 1-2 seconds, the speed quickly drops to about 1100 rpm and stays below this speed.

After 15-20 seconds, the tachometer indicates that the speed continues to decrease, but the speed of the speed decrease is significantly slower. Under normal circumstances, the speed of the engine decreases to 700-850 rpm and remains stable after 1 minute. (Different vehicle models will have different speed values, but the rules for speed changes should be roughly the same).

The working state of the engine tachometer should be changed with the change of the throttle. When the throttle is increased, the speed is increased; when the throttle is decreased, the speed is decreased; the throttle is stable and the speed is stable. Speed fluctuations under any circumstances are abnormal. Although some manufacturers' technical standards stipulate that the engine idle speed fluctuates 50 rpm, it is normal. However, during the actual use of the automobile, the engine idle speed fluctuates by 50 rpm, and the engine often has hidden troubles.

The relationship between the speed of the car and the stable speed of the engine on a smooth road:

The car speed is 40 km / h, and the engine speed is 1800-2000 rpm.

The speed is 60 km / h and the engine speed is 1900-2100 rpm.

The speed is 80 km / h and the engine speed is 2200-2400 rpm.

The speed is 100-120 km / h and the engine speed is 2500-2800 rpm.

Dashboard speedometer

The speedometer is used to indicate the speed of the vehicle. Speedometer accuracy is mainly affected by tire diameter. For example: tire wear, tire pressure, and tire slip.

Here we are mainly concerned about the relationship between engine speed and vehicle speed when the car is driving. Above we talked about the relationship between stable vehicle speed and stable engine speed. So, what should be the relationship between the speed of the engine and the speed of the car when the car is accelerating? For example: the corresponding shifting relationship of the car during acceleration from 0-100 km / h.

0 km / h engine speed 800 rpm

20 km / h engine speed 2500 rpm

40 km / h engine speed 2400 rpm

60 km / h engine speed 2300 rpm

80 km / h engine speed 2150 rpm

100 km / h engine speed 2000 rpm

Dashboard car oil level gauge

It mainly shows the amount of gasoline in the gas tank. This table is not generally a problem. It is worth noting that when the oil meter pointer is below the lowest red line, although the car can still travel 30-40 kilometers. But friends are advised not to wait until the oil meter pointer reaches the end or the oil level alarm light is on before refueling. Because cars use electric oil pumps. The electric oil pump in the fuel tank has poor heat dissipation effect when the amount of gasoline is small, which will reduce the service life of the oil pump. In addition, when some friends refuel, they like to add more gasoline after shaking the body. Not so good. If the fuel tank is overfilled, liquid gasoline may be sucked into the system when the car encounters unevenness and steep slopes, causing unnecessary trouble. ^[4]

Dashboard troubleshooting

Dashboard Disassembly

When the readings of automobile electrical instruments are abnormal, it may be possible to use wire removal method to check if there is a ground fault in the wires inside the sensor or between the sensor and the indicator. That is, the cause and location of the fault are judged by removing the wires on the related terminals. Take the electromagnetic fuel gauge as an example, when the ground or float inside the sensor is damaged, and the wire between the sensor and the fuel gauge is grounded, regardless of the amount of fuel in the fuel tank, the fuel gauge pointer always points to "0" after turning on the ignition switch. At this time, the disassembly method can be used for inspection. First, remove the wires from the sensor. If the fuel gauge pointer moves to I at this time, the internal iron or float of the sensor is damaged; if the pointer still points to 0, the sensor wiring on the fuel gauge should be removed If the pointer of the meter moves to "I", the wire of the fuel meter to the sensor will be grounded. If the pointer still does not move, the fuel meter may be damaged or its power cable may be disconnected.

Dashboard Grounding

When the readings of automobile electrical instruments are abnormal, through analysis and inference, it is possible that the sensor grounding is bad or damaged, and the wire between the sensor and the indicator meter is open-circuit fault, often the grounding method is used for inspection. Ground the relevant terminal posts through wires to determine the cause and location of the fault. After turning on the ignition switch, the fuel gauge pointer points to "I" for the electromagnetic fuel gauge regardless of the amount of fuel stored in the fuel tank; for bimetallic fuel gauges, the fuel gauge pointer points to "0", which indicates the corresponding instrument The sensor may have a bad ground or damage, or there is an open circuit fault between the sensor and the indicator. In this case, you can use the ground method to check. First, ground the terminal of the sensor connected to the wire. If the pointer rotates, it indicates that the sensor is damaged or the ground is poor. If the pointer does not rotate, the wire can be used to connect the indicator to the sensor. If the pointer is rotated, The wire between the sensor and the indicator has an open circuit fault; if the pointer still does not turn, it indicates that the indicator is damaged inside or its power cord is open.

Dashboard Shorting Method

When other electrical appliances are working normally, and only the instruments connected to the regulator (such as fuel gauges, electromagnetic water temperature meters, etc.) are not working, you can use the short-circuit method to check. Use a wire to short the input and output ends of the regulator. At this time, if the pointer of the meter connected to the regulator is deflected immediately, there is a fault in the regulator.