OBD
About the article

OBD-2 Analyser

Check out your car’s condition

OBD-2 Analyser
Modern cars are jam-packed with electronics. That’s great until something goes wrong. Then you’re at the mercy of the dealer. At least until now, because in many cases you can use the EOBD adapter described here to track down the problem yourself.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update
In certain cases the reset pulse is too short, causing the red LED to light only and the green and yellow LED to remain off all the time. Contrary to what is mentioned in the article text, it is better to fit IC7 and C7. A solder spot is available for the negative terminal of the electrolytic capacitor, while the positive terminal is connected to the centre pin of IC7.
Resistors:
R1,R2 = 1k
R3,R4 = 100
R5,R9,R15,R16,R21,R25 = 4k7
R6,R7,R8,R10,R11,R14,R17,R22,R23 = 10k
R12,R13 = 510
R18 = 1k1
R19 = 3k9
R20 = 3k
R24 = 1
Capacitors:
C1-C4 = 10µF 16V radial
C5,C6 = 27pF
C7 = 1µF 16V*
C8,C9,C10,C13,C14,C15 = 100nF
C11,C12 = 560pF
Semiconductors:
D1 = LED, high efficiency, green
D2 = LED, high efficiency, yellow
D6 = LED, high efficiency, red
D3 = 1N4001
D4,D5 = 1N4148
T1,T5 = 2N3906
T2,T3,T4 = 2N3904
IC1 = T89C51CC02UA, programmed, Publishers’ order code 050092-41 or from www.ozenelektronik.com; ref. type OE90C2600
IC2 = LM339 in DIL14 case
IC3 = PCA82C251 of PCA82C250, in DIL8 case
IC4 = MAX232, in DIL16 case
IC5 = LM7805C, in TO220 case
IC6 = LM7808C, in TO220 case
IC7 = ZSH560C, in TO92 case *
Miscellaneous:
K1 = 9-way sub-D socket (female), angled pins, PCB mount
K2 = 99-way sub-D plug (male), angled pins, PCB mount
JP1 = 2-way SIL pinheader
X1 = 16MHz quartz crystal, 32pF parallel capacitance
28-way PLCC socket
Case: Hammond type 1591B
RS232 extension cable, non crossed, (1:1) male-to-female
Adapter cable, female DB9 to OBD wired according to Figure 4. Available ready-made, Publishers order code 050092-72
PCB, Publishers order code 050092-1
A complete kit of parts is available from the Publishers; order code 050092-71
Content of kit:
- PCB
- programmed microcontroller
- all other parts
- OBD-to-DB9 adapter cable
- Case
* mount either C7 or IC7
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