Design of a 4-Way Traffic Light System using Flip-Flops
Traffic Control System
States:
Considering only a single set of traffic lights.
➢
S0 – Red Light
➢
S1 – Yellow Light
➢
S2 – Green Light
➢
S3 – Yellow Light
➢
S4 – Red Light
State Assignment:
➢
S0 – 000
➢
S1 – 001
➢
S2 – 010
➢
S3 – 011
➢
S4 – 100
Output:
➢
Red Bulb –
00
➢
Yellow Bulb –
01
➢
Green Bulb –
10
➢
Toggle Signal –
11
State Diagram:
Considering only a single set of traffic lights.
State Table:
Table 1: State table for a single
set of Traffic Lights
Present
State |
Input |
Next State |
T Flip-Flop |
Output |
|||||||
A |
B |
C |
x |
A |
B |
C |
TA |
TB |
TC |
y0 |
y1 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
0 |
0 |
1 |
1 |
0 |
1 |
0 |
0 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
0 |
1 |
0 |
0 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
0 |
0 |
1 |
0 |
1 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
0 |
1 |
0 |
0 |
1 |
1 |
1 |
0 |
1 |
0 |
1 |
1 |
1 |
1 |
0 |
0 |
1 |
1 |
1 |
0 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
1 |
1 |
0 |
0 |
1 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
1 |
Using K-Map:
Circuit Diagram for a Single Set of Traffic Lights:
This single set of Traffic Light circuit is taken as a single module in the following step to develop the complete system. The module has two inputs for Switch and the Clock with four outputs for the Bulbs and the Toggle Signal.
(Simulation Software – Logisim Version 2.7.1)
Combined Circuit Diagram for the Traffic Light System:
Figure 2: Combined Circuit Diagram for the Traffic Light System
In this complete system, the Traffic Control Module is the
above-developed circuit using T flip-flops. Here a single clock pulse is given
to each module using a demultiplexer. The demultiplexer outputs the
clock signal depending on the Select Line input. Select Line input is obtained
by a 2 – Bit Counter, where the counter increments its value depending on the
Toggle Signal.
When any one set of Traffic Lights reaches its final state, it outputs a Toggle Signal which results in an increment in the Counter. As a result, the Select Line value changes and therefore the demultiplexer outputs the Clock pulse to the next Traffic Control Module. At the end of the four modules, the counter reaches its maximum value and restarts resulting in a cyclic process. Several inputs can be connected as required using an OR gate.
(Simulation Software – Logisim Version 2.7.1)
Comments
Post a Comment