Basic knowledge of car computer board

1. Voltage signal
1. Analog voltage signal
The analog voltage signal changes continuously within a certain range. When using a varistor to control a 5V bulb, the varistor voltage may be any value between 0V-5V. If the varistor voltage is low, the current flowing through the bulb is small and the bulb is slightly bright. If the varistor voltage is 5V, the current increases and the brightness of the bulb increases. As the varistor voltage drops, the brightness of the bulb diminishes. This is an example of analog voltage (Figure 1).mostcarIn the computer systemsensorBoth generate analog voltages.
Note: The analog voltage signal changes continuously within the specified range.
2. Digital voltage signal
If the ordinary on/offswitchConnect to a 5V bulb, and when the switch is off, the voltage applied to the bulb is 0V. When the switch is turned on, a 5V voltage signal is applied to the bulb, and the bulb illuminates and reaches maximum brightness. If the switch is turned off, the voltage applied to the bulb returns to 0V, and the bulb goes out immediately. It can be seen that the voltage signal applied to the bulb is either 0V or 5V, or we can say that the voltage signal is either a high level or a low level. This voltage signal is called a digital signal. If the switch is quickly turned on and off, then the digital rectangular wave voltage signal is sent to the bulb via the switch (Figure 2). In car computers, the microprocessor includes many micro switches. These switches can generate many digital voltage signals every second.These digital voltage signals are used to control variousRelayAnd the time length of the component number in the system for precise control (Figure 3).
Note: Digital voltage signal is either high or low level; digital signal can be called rectangular wave signal.
3. Binary code
We have already said that digital signals are either high or low. Therefore, it is possible to assign values ​​to digital signals. For example, a low-level digital signal can be specified as 0, and a high-level digital signal can be specified as 1. Assigning values ​​to digital signals is called binary coding. The word "binary" means two numbers, and in a binary coding system, these two numbers are 0 and 1 respectively (Figure 4); in car computers, information is transmitted in binary codes. The status, quantity, and text can all be represented by a series of 0 and 1.
A lot of inputsensorWork in the range of 0V-5V.ThrottleThe voltage that the position sensor (TPS) can generate is:
Close sectionValve——0V-2V
Partially open the throttle-2V-4V
Wide Throttle-4V-5V
The computer can specify the value of each voltage as:
0V-2V——1
2V-4V——2
4V-5V——3
Note: Binary code is a combination of the numerical value of the digital signal.
2. Input adjustment
1. Zoom in
Some input sensors such as oxygen (O2) sensors only produce very low voltage signals less than 1V. Accordingly, a very small current is generated. Therefore, this signal must be amplified or amplified before being transmitted to the microprocessor. Amplification is completed by the amplifying circuit in the input adjustment of the computer (Figure 5).
Note: Amplification of the input signal means to increase the amplitude of these signals, and the increase will only be useful to the computer.
2. Analog/digital (A/D) conversion
Because the input sensor generates an analog signal and the microprocessor works as a digital signal, the analog signal must be converted into a digital signal. This work is done by the converter in the computer input adjustment chip (Figure 6).
The A/D converter continuously picks up the analog input signal at a constant time interval. If the A/D converter samples the throttle position sensor signal and the sampling voltage is 5V, the A/D converter first quantizes the sampled voltage, and then the A/D converter converts the quantized result into a binary code 11 (Figure 7 ).
Therefore, we can understand that the A/D converter continuously samples the input sensor signal and quantifies the sampled voltage. Then the A/D converter converts the quantized result into a binary code. In some car computers, the input adjustment chip is combined with the microprocessor.
Three, microprocessor
1. Structure
A microprocessor is a chip that performs calculations and judgments in a computer. There are thousands of triodes and industrial poles in the microprocessor, and these triodes function as electronic switches that can be turned on or off. The components in the microprocessor are etched on an integrated circuit (IC) board the size of a fingertip (Figure 8). The silicon chip carrying the integrated circuit is installed in a flat rectangular protective box. The metal connection pins are removed from the microprocessor box. Stretch out on both sides. These pins connect the microprocessor to the circuit board in the computer.
The microprocessor is supported by each memory chip, which stores information and assists the microprocessor in making decisions. The memory chip looks a lot like a microprocessor chip, and we will explain the function of the memory circuit board later.
Note: The microprocessor chip is a chip that performs calculations and judgments in a computer.
2. Procedure
The program is a set of instructions that can be accepted by the microprocessor, and the program brings the microprocessor into the judgment state. For example, the program can retrieve the information sent by the sensor through the microprocessor, and then tell the microprocessor how to process this information. Finally, the program will instruct the microprocessor to trigger output control devices such as relays or electromagnetic coils. Various memories store programs and other car data. The microprocessor uses these data to perform calculations. When the microprocessor performs calculations and judgments, the microprocessor and the memory work in the following ways:
1. The microprocessor reads information from the memory.
2. The microprocessor writes the new information into the memory.
3. Information storage
The memory has many different storage units. The simple element is similar to the folder in the file box, and each unit has 1 piece of information. Each storage unit is assigned an address. This address is similar to the arrangement of words or numbers on the folder. Each address is written in binary code, compiled sequentially from zero. When the engine is working, the computer receives a large amount of information from various sensors. It is impossible for a computer to process all this information at once. In addition, sometimes, the computer receives information from sensors that need to make some judgments. In this case, the microprocessor writes the information into the memory through the specified memory address and sends the information to the address (Figure 9).
4. Information Retrieval
When the information needs to be stored, the microprocessor specifies the storage address and requests to process the information. When the storage information at the specified address needs to be processed, the memory transmits a copy of this information to the microprocessor (Figure 10). The original stored information remains in the memory address. The memory stores the idle air-fuel ratio under various working conditions. The sensor informs the computer of the operating conditions of the engine and the car. The microprocessor reads the idle air-fuel ratio from the memory and compares it with the input of the sensor. After the comparison, the microprocessor makes the necessary decisions and controls the injector to provide the air-fuel ratio required by the engine.
Basic knowledge of car computer board