Page 173 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Table 7.1
Decimal
BCD
Binary
0 0000 0000
1 0001 0001
2 0010 0010
3 0011 0011
4 0100 0100
5 0101 0101
6 0110 0110
7 0111 0111
8 1000 1000
9 1001 1001
10 1010 0001 0000
11 1011 0001 0001
12 1100 0001 0010
13 1101 0001 0011
14 1110 0001 0100
15 1111 0001 0101
16 0001 0000 0001 0110
17 0001 0001 0001 0111
18 0001 0010 0001 1000
152 19 0001 0011 0001 1001
20 0001 0100 0010 0000

As you can see, the binary and BCD numbers remain the same until
reaching decimal 10. At decimal 10, BCD jumps to the upper nibble
and the lower nibble resets to zero. The binary numbers continue to
decimal 15, and then jump to the upper nibble at 16 where the lower
nibble resets. If a computer is expecting to read an 8-bit binary
number and BCD is provided, this will be the cause of errors.

Project 2: Interface circuit

The interface circuit revolves around the 4028 BCD integrated
circuit. The 4028 takes the lower BCD output from the 74LS373 on
the speech-recognition board and outputs a high signal; see the
truth table on 4028, Table 7.2.
The schematic for the interface circuit is shown in Fig. 7.6. The
inputs A, B, C, and D to the 4028 are the lower BCD numbers from
the 74LS373. When I stripped the car of its radio-control (R/C)
equipment, I was left with a group of wires that, when powered,
performed the basic driving functions. The robot car has just four
functions: forward straight, forward right, forward left, and reverse.
Team LRN
Chapter seven