This document describes a traffic light controller system with a central controller that communicates with local intersection controllers over a wireless network. It discusses the goals of designing an independent controller, implementing network coordination, and designing the central controller. It then provides details on the system overview, traffic control schemes, communication techniques, software implementation in the local controllers, and testing of the developed system.

1. Traffic Light Controller
Department of Electrical &
Electronic Engineering
Tiong Bing Yuhao Huang
Supervisor: Dr. Waleed H. Abdulla

2. Project Goals
Design an independent traffic light controller.
Implement network coordination
Design of central controller

3. System Overview
Local Transmit and Receive unit
Local intersection controller 1
Local Transmit and Receive unit
PC Central Transmit and Receive unit Local intersection controller 2
Local Transmit and Receive unit
Local intersection controller

4. Traffic Control Schemes
Pre-Timed
Vehicle Actuated
Coordinated Network

5. Serial Communication
MAX232 module
+/- 3.5 V
due to voltage
+/- 5 V swing
+/- 5V
Signal
RS-232 Signal inversion Transmitter
interface drive and pull module
up
Signal
inversion Signal Receiver
and pull dirve module
up

6. Central Transmit and Receive
Unit
Serial interface
Communication
devices.
(RF modules)

7. Communication Techniques
Amplitude Shift Keying
Frequency Shift Keying
(a) ASK
(b) FSK
(c) Binary signal
1 0 1

8. ASK Scheme
TWS-343 and RWS-434
Transmission
TWS-434
Transmitter
Reception
RWS-434
Receiver

9. Micro-processor M16
87 I/O ports
5 UART channels for serial communication
Technical support

10. Case Study

11. Phase Diagram
INTERSECTION LAYOUT
N Phase Group A B C D
5
MT. EDEN 1 OFF GAN OFF OFF
2 R R GAR R
6
3 7
3 GAR R R R
8 4 R R GAR R
ESSEX
ROAD 4
STOKES ROAD
5 SGGA SGAR R R
6 SOFF GAR R R
3
4
7 SGAR OFF OFF OFF
8
8
8 R/OFF R/OFF R/OFF GR
8
7
8 2
A preceding S means some form of special control of signal group.
5 6
2 1
Control Box
GAR – Green Amber Red GAN – Green Amber Off
R – Red R/OFF – Red or Off
1
Layout Info:
Start Phase : A
2 5 6
Phase sequences: BACD
Phase Groups:
4 Pedestrian
8
1
3 7
Vehicle Sensors: 1 2 3 4
5 6 7 8

12. The Developed System
Master controller
Two local intersection
controllers

13. Software Interface
Traffic control
schemes.
Intersection
feedbacks.

14. Communication Protocol
Between GUI – Local Controllers
Error control (maintain data integrity)
Access control (eliminates data collision)

15. Protocol Basics
Error Control : Checking digits on data
packet.
Parity bit & block sum check : Can only
detect single bit errors.
CRC : Cyclic Redundancy check, capable
of detecting burst errors.

16. Protocol Basics (continue..)
Access Control : Allocate link usage to the
communicating parties.
Token access control : Circulate data
transmission token to eliminate data
collisions

17. Token passing: operation
principles
Token
Data Data
Transmission Transmission
Equipment A Equipment B
DTE A wishes to send a data to the DTE B, it must first
wait for the receipt of the control token.

18. Token passing: operation
principles
Token Token
Data Data
Token passed
Transmission Transmission
with data-frame
Equipment A Equipment B
On receipt of the token, DTE A initiated transmission of
the frame and then passes the token to DTE B.

19. Token passing: operation
principles
Token
Data Data
Transmission Transmission
Equipment A Equipment B
DTE B has the token and therefore able to reply to DTE
A.

20. Token passing: operation
principles
Token Token
Data Data
Token passed
Transmission Transmission
back to DTE A
Equipment A Equipment B
On receipt of the token, DTE B initiated transmission of
the frame and then passes the token to DTE A.

21. Token passing: operation
principles
Token
Data Data
Transmission Transmission
Equipment A Equipment B
The process repeats itself whenever a data frame is
successfully passed between the two communicating
parties.

22. GUI-Local Controllers Protocol
Idle RQ ( idle repeat request )
Wait for acknowledgements from last
transmissions before sending another
frame.
Token access control
Enforce one party transmission rule.

23. Protocols Data Format
Sender Sender Sender
End of End of End of
message message message
Error control Error control Error control
message message message
Action/Data ACK NAK
Receiver Frame_size Receiver Data_Flow Receiver
identification identification identification
number number number
Sender Sender Sender
address address address
Start of Start of Start of
message message message
Receiver Receiver Receiver
b) acknowledgement c) negative
a) Data frame
frame acknowledgement frame

24. The Local Controller
Local transmit and receive
unit,
I/O ports and,
MCU (micro-controller.

25. MCU software implementation
Recognizing control commands.
Manages control of traffic signal.
Reporting intersection status.

26. Program Hierarchy
Main Program
Main Program
Signal control schemes
Signal control schemes
Communication
Communication Sensor
Sensor Timer
Timer
Interrupts Modules
Interrupts Modules Interrupts Modules
Interrupts Modules Interrupts Modules
Interrupts Modules
Data transmission.
Data transmission. Vehicle sensors.
Vehicle sensors. Countdown period
Countdown period
Data reception.
Data reception. Pedestrian button.
Pedestrian button. for red, amber and green.
for red, amber and green.

27. Signal Control Method
Starts control Phase Begin
d Pha Phase Terminate Gre
ire se T en
xp ime Group Tim
eE Phase B Exp Signal
e Exp
im ir ed i red
eT Green
as
Ph
eque red
sted
red
pi
Walk Time Ex
Expi
Group
No t R
Phase D Signal
Time
Phase A
pedestrian Amber
e
Phas
Red
Ph
as d
Wa e Ti Group ire
ed xp
lk R me xpir eE
eq Exp Phase C eE Signal
ue e Ti
m Ti m
ste ired Ph as Red b er
d Am

28. Testing of the system
Communication range 45cm, with the miniature
model intersection.
Reliable data communication between the local
controllers and the GUI master modules.

29. Limitations
Operating range and, (1-3 meters with line
of sight)
Speed of the communication devices. (3000
bits per second or 300 bytes per seconds)

30. Future Improvements
Network class protocols.
Better data transmission devices.
Sophisticated software interface for the
local controllers.

31. Conclusions
An independent Traffic light controller
based on the case study.
Final traffic control system is fully
operational.
Main project objectives are achieved.