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Speech Recognition 175

Vcc

R4
5.6KΩ
3
5 12
+
U3 2 U7d
4 LM339 9 10
– R3 10
R5 10KΩ 4049
15KΩ
U7c
7 6
9
4049
U7b
LED Input 5 4
8
4049
Vcc
1 14 U7a
U4a 3 3 2
A 2 4011 8 4049 7
U4c 10
9 4011
B 6
U4b 4 14 U6f 15
5 4011 6
C 4049
D Output
U6e
13 11 12 5
U4d 11
12 4011 Vcc 4049
U6d
R11 9 10
14 4
10 VDD U5 4.7KΩ Vcc 4049
3 RB4 4 24
11 RA4 MCLR' X1
D RB5 OSC1 16 7 U6c 6
15 4049 3
C OSC2 4MHz Q10 11
Q9 10
9
B Q8 8 U6b
2 RA3 RB3 9 20 Q7 7 5 4 2
1 8 21 D Q6 6 4049
A 18 RA2 RB2 7 22 C Q5 5
17 RA1 RB1 6 23 B Q4 4
RA0 RB0/INT A Q3 3
VSS 12 Q2 2 3 U6a 2
5 Q1 1
GND PIC16F84 18 19 Q0 1 4049
74154
Figure 11.7 Speech recognition interface (active high outputs) SRI­03.
resistors R4 and R5. The reference voltage is placed on pin 5 of the comparator.
Pin 4 of the comparator is connected to the LED lead on the speech recognition
circuit. Whenever a word is detected, the LED blinks off momentarily. The out­
put of the comparator (pin 2) is connected to pin 10 (RB4) of the 16F84 micro­
controller. The output of the comparator (pin 2) is usually high (�5 V). When a