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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING The diagnostic device is a trip computer. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices The diagnostic device - the trip computer performs the functions of the on-board computer (BC) of the car. It is designed to display in real time the parameters of the vehicle movement, the current time, the value of the selected parameter and the controller's fault codes, as well as to control the actuators of the engine management system with multiport fuel injection and the controllers "Bosch M 1.5.4" and "January - 5" both with and without an oxygen sensor. The BC scheme is shown in the figure. Its basis is the AT89S53-24PC (DD2) microcontroller. In contrast to the one used in the diagnostic device [1, 2], the BC is equipped with a microcontroller with a large amount (12 kB instead of 8) of FLASH memory.
To reliably start the microcontroller after power-up and block its operation when the supply voltage drops, the KR1171SP42 (DA1) microcircuit is used. It keeps the output (pin 3) low when the supply voltage is less than 4,2 V. Capacitor C3 delays the transition to the log state. 1 after the supply voltage exceeds this threshold. A complete functional and constructive analogue of the KR1171SP42 chip - PST529D from Mitsumi. In addition, taking into account a different pinout, this microcircuit is interchangeable with DS1233-15 from Dallas miconductor, ADM705 (Analog Devices), MAX705 (Maxim). In an extreme case, the KR1171SP42 microcircuit can not be installed at all. The reset signal will form the RC circuit R1C3. At the same time, it is advisable to increase the capacitance of the capacitor C3 to 1 μF and, in parallel with the resistor R1, connect any diode from the KD521, KD522 series with the cathode to the +5 V line. However, in this case, the device may malfunction with a sharp decrease in voltage ("failures") power supply. To display information, a single-line 16-character Russified LCD with LED backlight DV16110S1FBLY / R from Data Vision (HG1) was used. Although this instrument is designed to operate in an extended temperature range, it is powered in a "normal" way (a bipolar power supply is required to enable the extended temperature functions). The LCD can be replaced with a functional analogue from other manufacturers that meets the following requirements: the command system of its controller is compatible with KS0066, and the character generator is Russified. These conditions are met by JA-16101 LCDs from JE-AN Electronic, AC161B (Ampire), as well as indicators from Seico, Hantronic, etc. The BC is powered from the vehicle's on-board network, in which interference and significant power surges are possible. A number of additional elements are intended to exclude the influence of adverse factors. Diode VD8 KD248A protects the device from reverse polarity of the supply voltage. It can be replaced by any similar one with a permissible forward current of at least 300 mA, for example, 1N4001 from DC Components. To protect the BC from emissions in the on-board network, a special automotive varistor RU1 from S + M (Siemens Matsushita Components) SIOV S10K14AUTO was used. It can be replaced with a zener diode with a stabilization voltage of 15 ... 20 V, for example, KS515A, KS518A, etc. A BOURNS self-resetting fuse MF-R8 (F025) with a rated current of 1 mA is connected in series with the VD250 diode, which protects the device from emergencies due to possible short circuits in its circuits. In addition, to protect the power supply circuits of the +5 V BC as a result of the failure of the stabilizer (DA2), and such cases were noted during operation, a protective diode VD9 P6KE6.8 from Motorola was installed. This diode can be replaced with similar parameters 1.5KE6.8, SA5.0A of the same company or a zener diode with a stabilization voltage of 5,6 to 6,8 V, for example, KS456A. For additional sound indication of pressing buttons, changing the operating mode of the device, as well as warning about the controlled parameter going beyond the permissible limits, a sound generation unit (DD1.6, VT8, HA1) was used. Its main element is the HPM14AX piezoelectric emitter from JL World with a built-in generator operating at frequencies of 4300...5500 Hz. Therefore, to generate a sound, it is enough to apply a supply voltage of +12 V to it. This is performed by a switch on a Schmitt trigger DD1.6 and a transistor VT8. Since the current consumed by the emitter is approximately 15 mA, a transistor with a permissible collector current of at least this value can work in place of VT8. We will replace the emitter with HRM14A, HRM24A, HRM24AX or similar with a supply voltage of at least 12V. The signals from the speed and fuel consumption sensors are converted into TTL levels by interface nodes on transistors VT2 and VT3. The fronts of the received signals form Schmitt triggers DD1.2 and DD1.3. Diodes VD1-VD4 protect the BC inputs from possible voltage surges that exceed the supply voltage. For these purposes, you can use any low-power pulse diodes, for example, the KD521, KD522 series. The interface node with the diagnostic line (K-Line) is made on transistors VT7 (receiving key) and VT6 (transmitting key) and Schmitt triggers DD1.4, DD1.5. It converts signal levels from TTL to 12V according to the IS09141 specification. Diodes VD5 and VD6 protect the BC input from possible voltage surges on the diagnostic line that exceed the supply voltage. In their place, you can use any low-power pulse diodes, for example, KD510A or any KD521, KD522 series. Since, according to the IS09141 specification, the signal level is log. 0 can significantly exceed zero voltage, it is necessary to ensure reliable closing of the receiving key transistor at an input voltage of up to 3,3 V. This function is performed by the KS133A (VD7) zener diode. The DS1307 (DD3) microcircuit, which is a real-time clock with non-volatile memory, is used to form time stamps used in calculating the time parameters of the route, as well as to store these parameters when the BC power is off. The oscillator frequency of the DD3 chip is stabilized by a PK-206-1A 32768 Hz quartz resonator (ZQ2). When replacing a resonator with another, special attention should be paid to the fact that its capacitance should be close to 12,5 pF. Otherwise, the watch and trip computer may not work properly. In order to save the time parameters of the route and the value of the current time when the power is off, a backup source is used - a lithium cell CR2032 (G1) with a voltage of 3 V. It is permissible to replace it with any other cell or battery with the same voltage. Blocking capacitors C4 - C8 are located on the device board next to the chips DA1, DD2, LCD HG1, chip DD3 and connector XS1, respectively. The programmer is connected to the XS1 connector of the BC or connected to the PC parallel port socket. To eliminate the possibility of failures while writing a program to the microcontroller, the parallel port signals should be "powered up". For this purpose, buffer elements of the KR1533AP5 microcircuit are connected to the break in the lines of the connecting cable, which are powered from pin 2 (VCC +5 V line) of the XS1 connector. The BC control program consists of modules written in Assembler and C languages for the Keil compiler (Keil Electronic GmbH). The program was developed and compiled in the Keil mVision2 V2.04b integrated environment. Assembler - A51 version 6.00f, C compiler - C51 version 6.00i, linker - BL51 version 4.00d. The project file is mktstr.Uv2. Compiled program in Intel HEX format - mkt-str.hex. Before programming the microcontroller, it is necessary to check the correct installation of the BC, and then the serviceability of its main components. Without connecting the output of the DA2 stabilizer to the +5 V power line, apply the +12 V supply voltage and make sure that the stabilizer is working (there is a +5 V voltage at its output). Then check for a short between the +5V power line and ground. If there is no short circuit, connect the output of the DA2 stabilizer to the +5 V power line and make sure that there is voltage. After turning on the power at pin 9 (RST) of the DD2 microcontroller, a single pulse should be observed, and then a low level should be present all the time. Otherwise, the DA1 chip is most likely faulty. At pins 18 and 19 of the DD2 microcontroller, there must be a sinusoidal signal with a frequency of 24 MHz, and at pin 30 (ALE) - a meander (4 MHz). There are two ways to write a control program to the AT89S53-24PC microcontroller. First, by parallel programming using any universal programmer. This option is suitable if the microcontroller is not soldered to the board, but installed in the adapter panel. If the microcontroller is supposed to be programmed only in parallel mode, the XS1 connector, the VT1 transistor and the resistors R2, R3 can be excluded. Secondly, sequential programming using special ISP (In System Programming) programs, for example, Atmel AVR ISP. The serial programming option is preferable, since it does not require removing the microcontroller from the panel, and for automotive applications (in conditions of high vibration) it is desirable to solder it to the board. Check that the program memory is correctly addressed. At pin 29 (PME) DD2 should be high. If pulses are observed here - the microcontroller is working with external program memory - make sure there is a log. 1 at pin 31 (DEMA) DD2. If bursts of pulses periodically appear on the PME pin, the program goes beyond the internal memory, which should not be. Most likely the microcontroller is "clean" - the program is not written to it or written incorrectly. After the start, the control program initializes the serial port and the system timer of the microcontroller, and then initializes the LCD: it outputs command codes to port P2, accompanied by high-level pulses at the input E LCD. Having issued a command, the microcontroller puts all lines of port P2 into read mode and waits for a readiness signal from the LCD, continuing to supply single pulses to input E. If the indicator is faulty, the program "loops" on polling its readiness. After initialization, the LCD screen will clear and the splash screen will appear. If only black rectangles are visible on the screen, it is necessary to adjust the image contrast with a variable resistor R10. On the screen, black rectangles should not be visible or they should be barely noticeable. Simultaneously with the appearance of the screen saver, a low level appears at pin 35 (P0.4) of the DD2 microcontroller - the indicator backlight turns on. Then the control program configures the DD3 chip: a square wave with a frequency of 7 Hz appears at its pin 1 (SQW). If such a signal appears, then the microcircuit is programmed correctly. If there is no signal, but the BC works, most likely, a quartz resonator with an unsuitable capacitance is used and the clock and trip computer functions will not work correctly. When switching to the display modes of parameters, fault codes or control of actuators, the CU tries to establish communication with the engine controller. At pin 11 of the microcontroller DD2 every 300 ms, a low-level pulse with a duration of 25 ms appears, then after a 25 ms pause, several bytes of data are transmitted at a speed of 10400 bps. A similar signal, but with an amplitude of 12 V, should appear on pin 1 of the XS2 connector (K-Line). If there is no connection with the controller, the message "No connection" is displayed on the screen. The BC provides six modes of operation: clock, trip computer, indication of the value of the parameter selected by the user, indication and reset of controller fault codes, control of actuators and display of information about the device. Switch modes of operation by pressing the button SB4 "Mode". In clock mode, the indicator displays the current time in the HH:MM:SS format, where HH - hours, MM - minutes, SS - seconds. To correct the current time, it is necessary to press and hold down the "Select" button (SB3) for at least 1,5 s. First set the value of the hour, then the value of the minutes of the current time (the parameter to be changed flashes). The value of seconds is forced to zero. The hour/minute values are changed by pressing the buttons SB1 "Left" (decrease by 1) and SB2 "Right" (increase by 1). The parameter to be adjusted is changed by pressing the "Select" button. After the installation is completed, the BC returns to the current time display mode. In the trip computer mode, the following movement parameters are accumulated and displayed:
The displayed parameter is selected using the "Left" and "Right" buttons. To stop the calculation of route parameters (without resetting them), you need to press the "Select" button once. To resume the calculation of parameters, press the "Select" button again. Control the stop/start of parameter calculation by looking at the "route time". If the route parameters are not calculated, the seconds counter is stopped. To reset the parameters of the previous route, press and hold the "Select" button for at least 1,5 s. BC in the mode of viewing the value of the selected parameter indicates in real time one of the following variables:
In addition, the BC gives a sound signal when the displayed parameter is out of range:
The desired parameter is selected by pressing the buttons "Left" and "Right" BC in the mode of indication of fault codes in a cycle reads codes from the controller and displays their number on the LCD. If it is equal to zero (there are no faults), only the "Mode" button is available, when pressed, it exits the display mode of fault codes. If the codes are not there are correctness, to view them, press the "Select", "Left" or "Right" buttons. Scrolling through the read fault codes is carried out using the "Left" and "Right" buttons. To exit the mode of displaying fault codes without clearing them, press the "Mode" button. To erase fault codes, press the "Select" button and hold it for at least 1,5 s. In this case, the BC will erase all codes in the controller and read them again (after erasing, 0 faults should be read). Faults and their codes are given in [2]. The following components and assemblies are available in the actuator control mode:
In addition, the following engine parameters can be changed in this mode:
The transition from one node to another is carried out by pressing the "Left" and "Right" buttons. At the same time, for each unit, its current state is displayed (except for ignition coils and injectors). To switch to the control of the selected actuator, press the "Select" button. After that, you can change the state of the actuator by pressing once or by pressing and holding the "Left" and "Right" buttons. A change in the state of the unit is indicated by the symbol "*" (asterisk) in the first position on the LCD screen. To return control of the actuator to the controller, you must again press the "Select" button. When controlling any unit with the help of the BC, the controller loses the ability to "act" on it. Therefore, after switching to the control of the actuator (symbol "*" in the first position of the LCD screen), it is impossible to switch to another mode until control is returned to the controller by pressing the "Select" button again. The fuel pump control relay, ignition coils and injectors are only available when the ignition is on and the engine is not running. Pressing the Left button turns the fuel pump off, pressing the Right button turns it on. If it is not possible to control the fuel pump, the signs "-" (minus) are displayed instead of its status. When you press the "Select" button, 20 pulses with a duration of 5 ms with a pause of 5 ms are supplied to the ignition coil, and one pulse of a duration of 2 ms is applied to the injector. The operation of the ignition coil and injector is indicated by the symbols "***" (asterisks) on the LCD screen and by an audible signal. For control units with simultaneous injection, only the "Injector 1" mode is available. When you press the "Select" button in this case, the pulse will be applied simultaneously to the injectors of all cylinders. For control units with parallel injection in pairs, only the "Injector 1" and "Injector 2" modes are available. When you press the "Select" button in the "Injector 1" mode, the impulse is applied to the injectors of 1 and 4 cylinders, and in the "Injector 2" mode - to the injectors of 2 and 3 cylinders. All injectors are available for phased injection control units. Particular attention should be paid to the fact that for engines with simultaneous and pairwise parallel injection, it is not recommended to turn on the nozzles more than five times in a row, since the candles will be flooded with injected gasoline and subsequent engine start will be difficult (it is necessary to purge the cylinders by scrolling the engine with a fully open throttle for 20. ..30 s). Changing the CO correction factor is possible only for controllers in which a program is written that works without an oxygen sensor and a CO potentiometer (for example, M1V13R55, M1V13R59, M1V13R61). When you press the "Left" button, the CO correction factor decreases, and when you press the "Right" button, it increases by 0,003 units for a single press and 0,019 if the button is held down. The maximum lean mixture corresponds to a CO correction factor of -0,25 units, and the most enriched mixture - +0,25. Saving the changed value in the controller memory occurs when you press the "Select" button and is possible only when the CO-potentiometer is disabled (disabling the CO-potentiometer is recommended by AvtoVAZ specialists for programs that allow its absence), since the CO-potentiometer has a higher priority than the diagnostic equipment . When controlling the position of the idle speed control, pressing the Left button decreases, and pressing the Right button increases its current position by one step for a single press and five steps if the button is held down. In the position of the idle speed regulator, equal to 255 steps, its stem is fully inserted (the air channel is open, the speed is maximum), and in the position equal to 0 steps, the stem is fully extended (the air channel is closed, the engine is turned off). It is necessary to pay special attention to the fact that in the position of 0 steps on the idle speed regulator removed from the engine, the stem may fall out. When controlling the idle speed of the engine crankshaft, pressing the "Left" button decreases the frequency value, and pressing the "Right" button increases it by 10 min-1 for a single press and by 50 min-1 if the button is held down. It should also be noted that the engine is controlled according to the set idle speed, and the current value is displayed on the LCD screen. Therefore, there may be a delay in setting the frequency (the motor needs some time for the set frequency to become current). To switch to the mode of displaying information about the BC, you must turn off the ignition, press the "Mode" button and turn on the ignition, while holding the button down. In this mode, you can view information about the version of the device, programs and their authors. Scroll through the displayed information using the "Left" and "Right" buttons. To exit this mode, press the "Mode" button. If the car is not equipped with an immobilizer, the connection of the information line of the diagnostic interface (K-Line) of the controller with pin "M" of the diagnostic block, to which pin 1 of the XS2 connector of the device is connected, is usually broken. To install it, you need to install a jumper between pins 9 and 18 of the block to connect the immobilizer. If the car has already been diagnosed in a car service, most likely this jumper is already installed. Calculation of the distance traveled, speed and fuel consumption is carried out according to the signals of the speed and fuel consumption sensors of the engine management system. The signal from the speed sensor can be taken from pin 9 of the controller connector, and the signal from the fuel consumption sensor from pin 54. I recommend supplying power to the BC from the ignition switch - contact 27 of the controller connector. In this case, the device will automatically turn on when the ignition is turned on and turn off when turned off. In some vehicle configurations, a connector for connecting a trip computer is already installed, to which the power supply from the ignition switch and wires from the speed and fuel consumption sensors are connected. If there is such a connector, the BC should be connected to it. It should be noted that in the software of immobilizers released before March 2000, there is an error associated with possible desynchronization of information in the controller and immobilizer during the operation of diagnostic equipment. In this case, when carrying out diagnostics, it is necessary to transfer the immobilizer to the maintenance mode. Literature
Author: A. Alekhin
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