Outline
- Introduction
- Up Down Fading LED Lights Circuit Principle
- Up Down Fading LED Lights Circuit Diagram
- Components Required
- Up Down Fading LED Lights Circuit Design
- Link to Circuit Simulation Video
- How to Operate Up Down Fading LED Lights Circuit?
- Link to old Project Output Video
- Applications of Up Down Fading LED Lights Circuit
- Limitations of the Circuit
Introduction
I will demonstrate how to create an Up Down Fading LED Lights Circuit using very basic components in this LED-focused project. LED lights are gaining popularity due to their low cost, long lifespan, and energy efficiency.
LEDs have found various applications, including daytime running lights (DRLs) for cars, home decoration, standard lamps, emergency lighting, and more. One significant use case involves adjusting the brightness of LED lights based on the number of people entering or leaving a specific area or room.
This concept is referred to as LED fading, and I will provide a straightforward circuit that achieves a gradual fading effect on an LED.
Up Down Fading LED Lights Circuit Principle
The core elements of this circuit consist of a transistor and a capacitor. When the LED’s positive terminal is connected to the battery’s positive terminal, and the negative terminal is linked to the battery’s negative terminal, it operates under forward bias conditions.
Under this setup, the LED conducts only when the negative terminal is connected to the ground. Pressing the button initiates the charging and discharging of the capacitor, resulting in a gradual fading effect on the LED as it brightens and dims.
Up Down Fading LED Lights Circuit Diagram
Components Required
- Capacitor – 220μF
- Resistors
- 2 X 100KΩ
- 10KΩ
- 39KΩ
- 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 an On/Off switch, which takes the form of a push button. To place the button in the pull-down mode, a 10K resistor is connected following it. This setup ensures that the button initially stays in a low state, but it transitions to a high state when pressed.
Subsequently, the switch is linked to a 100K resistor, which is responsible for charging the 220F capacitor. Before reaching the transistor, there is a 39K resistor in the path for discharging the capacitor.
A parallel connection to the capacitor is made through a 100K resistor, allowing the 39K resistor to facilitate the discharge of the majority of the charge.
The transistor chosen for this application is an NPN transistor from the BC548 series. Initially, this NPN transistor remains in the off state, meaning it does not conduct. Only when a voltage is applied to the base region does the transistor permit voltage to flow from the emitter to the collector. It’s essential to note that the transistor’s base voltage must be at least 0.7 volts to trigger this behavior.
Once this voltage is supplied, the transistor begins conducting, and current flows from the emitter to the collector. To ensure that when the capacitor discharges, the charge only travels through the other resistors, a PN Junction Diode like the 1N4007 can be placed between the 100K resistor and the capacitor.
How to Operate Up Down Fading LED Lights Circuit?
1. To begin, turn on the circuit.
2. After that, press the button.
3. The LED appears to be fading up, indicating that its intensity is gradually increasing. When you press a button, voltage goes via a diode (not illustrated in the circuit) and then through a series of 100K resistors.
4. The parallel capacitor connected to the resistor is charged. This provides a voltage to the transistor’s base, which subsequently begins to conduct.
5. As a result, voltage from the collector travels to the emitter, which is grounded.
6.Thus, negative terminal of the LED is connected to the ground.
7. As the capacitor continues to create pulses, the LED gradually begins to illuminate.
8. As the capacitor is exhausted, the LED progressively fades out when the switch is released.
9. A 36K resistor is present before the transistor, so that the capacitor discharges through this resistance while discharging.
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.
