Report on Traffic Light System Using NE555 Timers
IE1044 Digital Electronics
1st year 2nd semester - 2024
Student Name: Mohamed Mufassir
Student ID: IT23650848
Student Name: Mohamed Falil
Student ID: IT23426108
Report on Traffic Light System Using NE555 Timers
Introduction
This report is about the traffic light system which we have made for our semester 2
project o Digital Electronics module. This circuit system is vital for managing traffic flow
and ensuring safety at intersections. This project focuses on making the traffic light
system using NE555 timer ICs. According to the theory We can conclude the two ICs are
in astable mode. But, according to the functions of two ICs we can say first IC is in
astable mode and second IC in monostable mode (because it works like triggering by IC
1’s output).
The system emulates the real-world traffic light behavior by sequentially lighting up
Green, Yellow, Red, Red and Yellow LED’s. The main objective of the project is
understanding the operations of NE555 timers and apply digital electronics principles to
manage the timing ideas. The design also includes the idea of the potentiometers which
provide flexibilities to fine tune for getting the correct duration of output states.
Components Description
We have suggested to do the circuit with an instruction sheet which has include All
instructions. And we have studied each component’s roles and what it should do.
Component Quantity Description
Configured in astable mode to generate square wave signals for LED
NE555 Timer 2
control.
LEDs (Red, Yellow,
3 Represent the traffic light states.
Green)
Potentiometers (100K) 2 Adjustable resistors to control timing intervals for each traffic state.
Capacitors (100µF) 2 Stabilize the NE555 timers and determine timing intervals.
Resistors (220Ω, 47KΩ) 3 Limit current to LEDs and set timing parameters for NE555 timers.
Breadboard 1 Used for assembling and testing the circuit.
12V Power Supply 1 Provides power to the circuit.
Circuit Design and Diagram
The circuit uses two NE555 timers –
• IC1 (Timer 1): Controls the red LED and the red + yellow state. It determines the duration of these states
using a resistor, capacitor, and potentiometer combination. (astable mode)
• IC2 (Timer 2): Controls the green and yellow LEDs. The discharge pin activates the yellow LED, while
the output pin powers the green LED. (Act like a monostable mode)
100 μF
100 μF
Design Formula
The timing intervals for each timer were calculated using the NE555 formula:
T=0.693×(R1+2R2)×CT = 0.693 \ times (R1 + 2R2) \ times CT=0.693×(R1+2R2)×C
where:
• TTT: Time period for each LED state
• R1,R2R1, R2R1,R2: Resistor values
• CCC: Capacitor value (100µF)
Those formulas are used to determine the correct timing effect of out circuit. Also it
could be changed with the outer effects (outer resistance)
Operation Analysis
The system cycles trough the following states –
State LED Status Description Timing Output Pins
State 1 Green ON Vehicles can proceed T1 (5 seconds, adjustable) IC2 Output HIGH, IC1 LOW
State 2 Yellow ON Prepare to stop T2 (2 seconds, adjustable) IC2 Discharge ACTIVE
State 3 Red ON Vehicles must stop T1 (5 seconds, adjustable) IC1 Output HIGH
State 4 Red + Yellow ON Prepare to go T2 (2 seconds, adjustable) IC1 & IC2 Outputs HIGH
Testing and Observation
The circuit was assembled on a breadboard, and the following results were observed:
State 1 → Green LED is ON
State 2 → Yellow LED is ON
State 3 → Red LED is ON
State 4 → Red and Yellow LED’s ON simultaneously
- We can Adjust the timing of LED’s by adjusting the Potentiometers
- Potentiometer 1 → Controls the duration of the Red LED in State 3 and influences State 1
(Green LED).
- Potentiometer 2 → Controls the duration of the Yellow LED in State 2 and influences the Green
LED in State 1.
Observations:
• The traffic light system transitioned smoothly between states.
• Timing intervals were consistent and adjustable using the potentiometers.
• LEDs functioned without interruptions or flickering.
Reflection
Challenges –
• Synchronizing the timing intervals between the two NE555 timers should be
in the correct tuning of potentiometers
• Getting the correct transitions durations and getting correctly the STATE 3
(Red and Yellow Both ON)
Lessons learned –
• We have got a clear understanding of 3 modes of the NE555 timer IC and
How the astable, Monostable, Bistable works.
• Developed our understanding of timing circuits and their practical
applications.
Future Improvements we can make –
• With this circuit idea, combine another thing to improve the circuit with pedestrian
crossing signal.
• Implement a microcontroller- based system for more advanced features like
adaptive timing
Conclusion
This project successfully achieved its goal of designing a traffic light system using
NE555 timers. The hardware implementation reflects a smooth transition through all
states, with adjustable timing intervals. This practical experience taught us to have a
deeper understanding about Digital Electronics and NE555 Timings.
References
https://www.youtube.com/channel/UCBkOVp1Cqz4MR0LYR8vKpZg
https://elonics.org/model-traffic-lights-circuit-using-555-ic/
