ELM ELM327 - Page 71

+ +
R36*
22KΩ
Figure 12.
Modifications to reduce power
2 (RxD)
X1
4.00MHz
C4
27pF
RS232
Interface
(DB9F)
OBD
Interface
R27-30
470Ω
+5V
C3
27pF
+5V
+5V
+5V
3 (TxD)
5 (SG)
1 (DCD)
4 (DTR)
6 (DSR)
7 (RTS)
8 (CTS)
+5V
+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
PWR
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
Vbat +12V
Signal
Ground
5
+5V
R1
470Ω
C6
0.1µF
C1
0.1µF
D1
R26
4.7KΩ
R24
10KΩ
R25
10KΩ
D4
D5
C5
0.1µF
R23
4.7KΩ
R22
10KΩ
Q8
Q9
L1-L4
L5
R32
100Ω
R33
100Ω
C8
560pF
C9
560pF
R31
4.7KΩ
C7
0.1µF
R19
510Ω
R17
510Ω
R18 2.2KΩ
R20
47KΩ
R21*
22KΩ
R34
47KΩ
R35
10KΩ
C2
0.1µF
22KΩ
4.7KΩ
47KΩ
R8
10KΩ
R7
4.7KΩ
Q1
Q2
R6
4.7KΩ
R10
22KΩ
R9 10KΩ
R11
10KΩ
R12
100KΩ
D3
Q4
R13
10KΩ
R14
4.7KΩ
Q3
D2
Q6
Q7
U2
U3
* see text
LP2950
5.0V
TVS
4.7µF
10V
2.2µF
50V
+
4.7µF
16V
1
2
4
3
R16 2.2KΩ
1
2
3
4
5
6
7
8
LP2951
71 of 76
ELM327
ELM327DSH Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
U4