Design of Traffic Light System

Contents

 

LIST IN Tab;e

 

List in Figure

 

Design Specification

Design specification prepared for a single main and sub -road junction in rural area is given below

• The green light for the main road will be stay ON for 30s.

• The green light for the side road will be stay ON for 20s.
• The amber caution light will say ON for 5s between changes from green to red.
• Main road and side road timing countdown should display in a 7segment display.
• Sequence change of the traffic lights show in the Appendix I.

The traffic light system for a single main road and sub road junction in a rural area.

Complete Block Diagram of the traffic light system

                  Figure 2(block diagrammed)

The FSM description stands for “Finite state machines”. the Finite state machines are the most common controllers of machines. It’s In the example Traffic light, the intersection of a main road with a side road is controlled by two traffic lights. FSM has three inputs (T1, T2 and T3) AND six outputs (Rm, Am, Gm, Rs, As and Gs)

In here

Rm is Red light for main road

Am is Amber caution light for main road

Gm is Green light for main road

Rs is Red light for sub road

As is Amber caution light for sub road

Gs is green light for sub road

T1 time is 30seconds

T2 time is 20seconds

T3 time is 5seconds

Complete Moore model state diagram for traffic light system

State diagram Table

P.State	N.State	INPUT	Outputs
			Gm	Am	Rm	Gs	As	Rs
			1					1
		T1
				1			1	1
		T3
					1	1
		T2
				1	1		1
		T3

Table 1(State diagramme)

State Assignment in Gray code

Here using gray code for states

State transection table

Here using D type flip flops for design a circuit

P.S Q1  Q0	N.S Q1+   Q0+	INPUT
					Gm	Am	Rm	Gs	As	Rs
0       0	0        0				1					1
	0        1	T1		1
0       1	0        1			1		1			1	1
	1        1	T3	1	1
1       1	1        1		1	1			1	1
	1        0	T2	1
1       0	1        0		1			1	1		1
	0        0	T3

Table 2(D type Flip Flop)

Simplified equations for the system.

From Laws of Boolean Algebra

(

The equations are,

Circuit simulation using Multisim software,

Figure 4 (main red and sub green for 10s)

                                               

Figure 5 (Main amber and sub red and amber for 2s)

Figure 6(main red and sub green for 10s)

Timing Counter

                         Figure 10 Main green and sub red

Figure 11 (Main amber and sub red and amber)

Figure 12 (Main red and sub green)

Figure 13  (Main red and amber sub amber)

Task 4

Item name	quantity	Price (Rs)
2 pin AND gate IC	5	120Ã-5=600
3 pin AND gate IC	2	120Ã-2=240
2 pin OR gate IC	1	40Ã-4=40
3 pin OR gate IC	1	40Ã-1=40
2 pin XOR gate IC	1	40Ã-1=40
Dual JK FF IC	10	100Ã-10=1000
Dual D FF IC	1	100Ã-1=100
DCD 7 Segment decoder IC	5	100Ã-5=500
7 Segment display	5	50Ã-5=250
NOT gate IC	2	40Ã-2=80
Red color LED	2	5Ã-2=10
Amber color LED	2	5Ã-2=10
Green color LED	2	5Ã-2=10
wires	20m	15Ã-20=300
Power adaptor	2	150Ã-2=300
Total	3420

      Table 3(design cost)

Remake design

Figure 14(remake design)

Compare the cost

Item name	Previous cost (Rs)	New cost(Rs)
2 pin AND gate IC	1Ã-120 = 120	1Ã-120 = 120
3 pin AND gate IC	1Ã-120 = 120
XOR gate IC	1Ã- 40 = 40
D type FF IC	1Ã-100 = 100	1Ã-100 = 100
Decoder IC		1Ã-100 = 100
NOT gate IC	1Ã- 40 = 40	2Ã- 40 = 40
OR gate Ic	1Ã- 40 = 40	1Ã- 40 = 40
total	460	400
Table 4(compare table)

• In new design cost is less than old design

Reference

Mano M.M,Michael D.C. (2008).Digital Design.New Delhi:PHI.

Floyd,L.(2011).Digital Fundamentals.10th ed.India:Pearson. p271- 287.

http://www.topssrilanka.com/article24948-new-traffic-ligth-system-atbambalapitiya.html.Lasr

http://www.sundayobserver.lk/2012/06/03/imp01.asp