UP AND DOWN FADING OF LED

THIS IS A PROJECT DONE BY USING SMALL ELECTRONICS COMPONENTS AND BY DOING THIS WE CAN SEE THE FADING OF LED BY UP AND DOWN AND FOR THIS WE MADE REPORT IN A SPECIFIED WAY AND IN THIS IS WE SHOWN EVERY STEP BRIEFLY HOW TO DO THE PROJECT AND THE RESULTS ARE ALSO COMING AND THIS PROJECT IS USEFUL FOR MANY TO DO PROJECTS

1. MINI PROJECT REPORT
On
UP AND DOWN FADING OF LED
Submitted as a part of Second Year First Semester
curriculum of
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL AND ELECTRONICS ENGINEERING

By
Mr.P.Eswar Sai 18981A0237
Mr. P.Mohan Kumar 18981A0238
Ms. P.Supriya 18981A0239
Mr. P. Nithesh Kumar 18981A0240
Mr. P.Sanjay Kumar 18981A0241
Under the Supervision of
Mr. Ravi Tejaswi
Associate Professor

Department of Electrical & Electronics Engineering
Raghu Engineering College
(Autonomous)
Accredited by NBA & NAAC with ‘A Grade, Permanently Affiliated
JNTU Kakinada
Dakamarri (v), Bheemunipatnam Mandal, Visakhapatnam, Andhra
Pradesh 531162

Oct – 2019

2. RAGHU ENGINEERING COLLEGE
Department of Electrical and Electronics
Engineering



CERTIFICATE

This is to certify that case study entitled as “UP AND DOWN
FADING OF LED” submitted by Mr.P.Eswarsai (18981A0237), Mr.P.Mohan
Kumar (18981A0238), Ms.P.Supriya(18981A0239), Mr.
P.NitheshKumar(18981A0240), Mr.P.Sanjay Kumar(18981A0241) as a part of
Second Year First Semester Curriculum of Under Graduate Program
in Electrical & Electronics Engineering at Raghu Engineering
College.






Faculty Member Head of the department
Mr . Ravi Tejaswi Dr P. Sasi Kiran
Associate Professor Professor

3. UP/DOWN Fading LED Lights
Introduction
In this LED based project, I will show you how to design an Up Down
Fading LED Circuit using very simple hardware. Nowadays, the usage
of LED lights is increasing rapidly because of their reduced cost and
long durability (of course their low power consumption).
Generally, you can see various implementations like Automobile DRLs
(Daytime Running Lights), decorating houses, regular lamps,
emergency lights etc.
One such important application is where the LED lights increase and
decrease their intensity depending on the number of persons entering
or leaving at a particular place or a room.
This concept is called Fading of LEDs. Here is a simple circuit where an
LED slowly fades out when it is applied with some voltage.

4. Up Down Fading LED Lights Circuit Principle
The circuit mainly consists of a transistor and a capacitor. Light
Emitting Diode conducts in forward bias condition i.e. LED glows only
when positive terminal is connected to the positive end and negative
end is connected to the negative of the battery.
In this circuit, LED conducts only when the negative terminal is
grounded as the positive terminal is applied with some voltage. When
the button is pressed, the capacitor starts charging and discharging
which causes the LED to fade up and down.
Up Down Fading LED Lights Circuit Diagram

Components Required
• Capacitor – 220μF
• Resistors
2 X 100KΩ
10KΩ
39KΩ

5. 100Ω
• BC 548 (any NPN Transistor)
• LED
• ON/OFF switch (Push Button)
• Mini Breadboard
• 5V Power Supply
• Connecting Wires

Up Down Fading LED Lights Circuit Design
In this circuit, the power supply is connected to the On/Off switch i.e.
a push button. A 10KΩ resistor is connected after the button to bring
the button to the pull down mode. This makes the button initially low
and when it is pressed, it becomes high.
Switch is then connected to a resistor of resistance 100KΩ, which is
responsible for charging the 220μF Capacitor. Another resistor of
39KΩ is connected before the transistor, through which the Capacitor
discharges.
A 100KΩ Resistor is connected in parallel to the capacitor so that
majority of the charge is discharged through the 39KΩ Resistor.
Transistor used here is a NPN transistor of series BC548. This NPN
transistor is initially in off state i.e. it will not conduct. Voltage from
emitter to collector flows, only if the base region is applied with some
voltage. The minimum voltage required at the base of the transistor is
0.7V.
When this voltage is applied, transistor starts conducting and voltage
starts flow from emitter to collector. You may get more knowledge on

6. NPN Transistor by reading the post – Transistor Biasing and
Characteristics
A PN Junction Diode like 1N4007 can be placed between the 100KΩ
Resistor and the capacitor so that when discharging, the capacitor
charge flows only through the other resistors.
How to Operate Up Down Fading LED Lights
Circuit?
1. Initially, switch on the circuit.
2. Then press the button.
3. You can see the LED fading up i.e. slowly its intensity increases.
When a button is pressed, voltage flows through the diode (not
shown in the circuit) and it then flows through a series of resistor
having 100KΩ.
4. The capacitor connected in parallel to the resistor is charged.
This gives some voltage to the base of the transistor which then
starts conducting.
5. Thus, voltage from collector flows to the emitter, which is
connected to the ground.
6. Thus, negative terminal of the LED is connected to the ground.
7. And LED slowly starts glowing, as the capacitor continuously
produces the pulses.
8. Before the transistor, a resistor of 36KΩ is present so that while
discharging, the capacitor discharges through this resistor.

7. Applications of Up Down Fading LED
Lights Circuit
• This can be used in the shopping malls for fading out the lights
in the places where there is no crowd.
• Fading LEDs can be used in security applications to alert
something.
• These can be used in home applications.
• These can be used in cars as indicators with some changes.
Limitations of the Circuit
• LED lights should be powered correct voltage otherwise they
may be damaged.
• LEDs can change color due to age and temperature.