ELM327
CAN-L
14
U3
LP2950
+5V
Vbat
+12V
+
6
16
Battery
Positive
CAN-H
R22
R23
D1
+
8
1
7
6
5
R24
4.7KW
100W
100W
D4
5.0V
TVS
C5
C6
C7
10µF
10V
2.2µF
50V
0.1µF
50V
C8
560pF
50V
C9
560pF
50V
MCP2551
+5V
5
Signal
Ground
2
3
4
U2
C1
0.1µF
+5V
Vbat Vbat
L5
R19
510W
R17
510W
R31
470W
15
U5
ISO-L
R16 2.2KW
1 (DCD)
4 (DTR)
6 (DSR)
Q6
7
+5V
ISO-K
R18 2.2KW
7 (RTS)
8 (CTS)
Q7
R32
+5V
USB
Interface
(mini B)
4.7KW
D5
ELM327
pin 12
3 (TxD)
2 (RxD)
R20
47KW
R21
33KW
L1-L4
5 (SG)
9 (RI)
R27-30
470W
+5V
+5V
Vbat
FTDI
DB9-USB-D5-F
28
27
26
25
24
23
22
21
20
19
10
18
17
12
16
13
15
U1
R25
47KW
327
+5V
1
2
3
4
5
6
7
8
9
11
14
R26
10KW
C2
0.1µF
to
R15
to
R21
+12V
X1
U4
4.00MHz
Out
In
OBD
Interface
(J1962)
R2
317L
Adj
C3
27pF
C4
2.2KW
R5
470W
27pF
R3 470W
R8
10KW
R4
2.2KW
R6
4.7KW
Q2
R10
22KW
R7
4.7KW
Figure 9.
An OBD to USB Interpreter
Q1
D2
R9
10KW
2
J1850 Bus +
R1
22KW
R11
10KW
+5V
10
R14
4.7KW
J1850 Bus -
R12
47KW
D3
R15
4.7KW
Q4
ELM327
pin 14
Q3
Q5
R13
10KW
ELM327DSI
Elm Electronics – Circuits for the Hobbyist
73 of 82
www.elmelectronics.com
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