Operation Manual

Figure 9.
An OBD to USB Interpreter
80 of 94
ELM327
ELM327DSJ Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
R10
22KΩ
X1
4.00MHz
C4
27pF
OBD
Interface
R27-30
470Ω
+5V
C3
27pF
+5V
+5V
317L
+12V
ELM327
pin 14
R15
4.7KΩ
to
R15
+5V
(J1962)
J1850 Bus +
2
J1850 Bus -
10
Q5
to
R21
+5V
+5V
CAN-H
6
CAN-L
14
1
2
3
4
5
6
7
8
MCP2551
Vbat Vbat
ISO-L
15
ISO-K
7
ELM327
pin 12
Vbat
327
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
U1
Battery
Positive
16
7805
Vbat +12V
Signal
Ground
5
C5
0.1µF
D1
L1-L4
R31
470Ω
L5
R22
100Ω
R23
100Ω
C7
560pF
50V
C8
560pF
50V
R24
4.7KΩ
C6
0.1µF
R19
510Ω
R17
510Ω
R16 2.2KΩ
R18 2.2KΩ
R20
47KΩ
R21
33KΩ
R25
47KΩ
R26
10KΩ
C2
0.1µF
R5
470Ω
R3 470Ω
R4
2.2KΩ
R2
2.2KΩ
R6
10KΩ
R7
4.7KΩ
Q1
Q2
R1
4.7KΩ
R8
22KΩ
R9
10KΩ
R11
10KΩ
R12
47KΩ
D3
Q4
R13
10KΩ
R14
4.7KΩ
Q3
D2
Q6
Q7
U2
U3
U4
R32
4.7KΩ
USB
Interface
(mini B)
3 (TxD)
5 (SG)
1 (DCD)
4 (DTR)
6 (DSR)
7 (RTS)
8 (CTS)
FTDI
DB9-USB-D5-F
9 (RI)
2 (RxD)
+5V
D4
U5
+5V
C1
0.1µF
50V
In
Out
Adj
n.c.
n.c.