The project is a device with an external interface connector for OBD2, which provides easy access to the CAN bus and other transmission lines, used by vehicle manufacturers for the diagnosis.
recommendations: device is intended for car workshops, involved in the diagnosis.
Looking for new cars, hard to imagine them without modern electronics. More and more new solutions, invented by engineers all over the world, We are fast approaching, until the driver ceases to be the most important "element", determining vehicle behavior in unexpected situations on the road. Directed by sci-fi movies have predicted the future of modern vehicles a long time ago. The films were shown cars without driver, in which passengers sit in the car, I told, where he wants to go, and the driver of "robot" drove it to the specified point without incident. Within a few years, Google has been testing its autonomous car without a driver on the streets of the US. Management is replaced by computer, equipped with various sensors, including: GPS, proximity sensors, external scanners, radar or camera LIDAR. The most interesting, The car, directions several years without direct supervision and overcome a thousand kilometers, only a few times collided with another car, and, it was caused by other motorists!
The rapid development of new technologies and electronic components can increase the data rate and to develop error-free transmission protocols, which contributes to the creation of more safe cars. Not so long ago the computer, displaying even an average fuel flow rate, It was reserved only for the most expensive version of the car models. All this technological development contributed to the development of electronic systems, allowing to diagnose vehicles: a vehicle installation may be up 5 Independent gear tires. The new cars often CAN bus is used. A huge number of installed sensors compels to use fast and reliable data bus and connecting them together. Insertion of the data bus, after which the parameters are sent from all of the sensors, installed in the car, also allowed the self-diagnose car. CAN bus, responsible, For example, for communication schemes, ensuring the operation of the engine, comfort or security schemes schemes, connected to the external interface, which can connect the diagnostic tester, and data, sent by the sensors and electronic modules, They should be checked, and records can be read and detected errors, arising during operation. Tires are connected to each other via an interface, available to the diagnostician (Gate-Way), ending 16-pin connector OBDII diagnostic, shown in Figure. 1.
OBDII is the standard, applicable to all vehicles, produced after the 1 January 1996 in the United States and after 1 January 2003 year in the European Union. One of the most important advantages of CAN interface is, that all electronic modules and sensors in a given subnet are connected in parallel to the 2-wire twisted pair, which reduces the weight and cost of installation. A simplified diagram of CAN bus topology, used in vehicles, shown in Figure 2.
All electronic modules are connected in parallel to the two-wire twisted pair. Data are transmitted on a twisted pair differential signal via, whereby the signal has an increased resistance to external electromagnetic interference. To eliminate reflections waves on both ends of the bus are used with impedance matching resistors 120 ohm. They may vary depending on the data rate and the type of twisted-pair. The CAN device has two output labeled CAN High and CAN Low. When no information is transmitted on the bus (recessive state), both lines there is tension 2,5 AT. During transmission, (the dominant state) voltage change to 1,5 In line for Low and up 3,5 V for line High (picture 3). It is worth to know the basic information about the data transmission using CAN.
Design and function
The presented design is an external interface OBDII connector, which allows easy access to the CAN bus and other transmission lines, used vehicle manufacturers. OB-DII connector on all cars, released after 2003 of the year, usually installed under the steering wheel – an example is shown in Figure. 4.
On the picture 5 shows an arrangement of pins in the diagnostic connector OBDII.
Some of the findings can be used by car manufacturers for their own communication protocols. Signal analysis directly from the connector is very inconvenient because of its location. Presented CAN-BOX provides easy access to 16 OBDII diagnostic connector contacts. diagnostic equipment, analyzers CAN bus data, oscilloscope or diagnostic tester can be connected to the terminals, making it easy to diagnose errors, transmitted by the electronic modules of the car.
On the picture 6 shows an example of the diagnostic tools to the vehicle wiring diagrams, and Figure. 7 shows the practical use of the vehicle.
CAN-BOX also simplifies the connection of the electronic module, removed from the car, and his diagnosis is, according to the diagram in Figure 8.
On the picture 9 It contains the motor controller, connected via CAN-BOX cables, through which he can save or read the data from the contents of the memory.
Nutrition CAN-BOX can be done in two ways: through the diagnostic connector OBDII or from laboratory supply. Both the power line protected by a rectifier diode, protecting operating diagnostic equipment from reverse polarity of the supply voltage.
On the picture 10 is a schematic diagram of the device.
Diode D1 protects diagnostic tester, connected to the OBDII connector, indicated on the «OUT» circuit, Reverse polarity, which may occur in the vehicle OBD2 connector. The diode D2 protects the diagnostic tester, connected to the OBDII connector, marked on the concept of «OUT OUT», reverse connection of the external power source to connectors of type «BATT +» and «GND». The device uses two LEDs. LED with «OBDII» marking indicates the voltage, occurs at the contacts 16 (plus power supply) and 4 (frame ground), CAN-BOX when connected to the vehicle connector OBDII, and the LED «Batt» marking indicates the external voltage, applied to the terminals 4 and 16.
Building and installing
CAN-BOX assembly board is shown in Figure 11.
LEDs should be bent and soldered, as shown in Figure. 12.
OBDII connector and socket must be soldered to the circuit boards attached, paying attention to the numbered terminals, as described in boards (rice. 13) and rice. 14). The most difficult task in the assembly can be accurate soldering of printed circuit boards, components of housing.
Along the perimeter of the plates is tinned layer, which is intended for soldering therebetween (rice. 15 and 16).
4 side plates with the socket should be brazed together. Lower board must be screwed to the metallic spacers using 4 screws for easy removal and access to the inner part. During this operation, pay attention to the correct positioning of the socket (OUT) and forks (IN). After soldering, circuit board housing via wires or angular gilt contacts connect terminals IN and OUT connectors to soldering points, located on the panel connectors.
After proper and accurate solder circuit activation consists essentially of checking assembly for shorted, and then connecting the power supply +12 In your contacts 4 (minus) and 16 (a plus) OBDII IN connector and check “OBDII” included. Then switch the power supply 12 B 4 (minus) and 16 (a plus) sockets and check, Do LED lights «Batt». Before connecting the diagnostic tool is worth checking the correctness of the transition of the signal from input to output. This is best done with the help of the measuring device, provided with a beep, touching contact probes with "1" in the plug OBDII, marked «IN», and track "1" in slot OBDII, marked «OUT». Repeat this procedure for all of the contacts in both plugs. After these operations, CAN-BOX is ready for use.