Running led lights circuit diagram

 In this blog post, we’ll walk you through the process of creating a running LED light circuit using three 2N2222 transistors and 19 LEDs. This is a popular project for electronics enthusiasts who want to add a cool lighting effect to their projects, such as for decorations, display boards, or toys. The running light effect creates a sequential "chasing" pattern with the LEDs, giving a visually appealing motion-like effect.

Running led lights circuit diagram

Components Needed:

  • 19 LEDs (Light Emitting Diodes) – preferably of different colors for a more dynamic visual effect
  • 3 Transistors (2N2222 NPN) – widely used for switching and amplification purposes
  • Resistors:
    • 3 current-limiting resistors (330Ω to 1kΩ) to protect the LEDs
    • 3 bias resistors for the base of the transistors (10kΩ)
  • Capacitors – (100μF or 150μF) to smooth out the switching transitions
  • Breadboard or PCB for assembling the circuit
  • Power Supply (12V to 24V) depending on the type of LEDs used

Understanding the Concept:

In this circuit, we use three transistors to drive the 19 LEDs in a cascading or running sequence. The circuit works by switching the transistors on and off in a sequence, which in turn lights up the LEDs one by one. By controlling the timing between the LEDs lighting up, we create a “running” or “chasing” effect.

Each 2N2222 transistor will be used as a switch to drive several LEDs, and the three transistors will be connected in a multivibrator configuration to alternate the output among the LEDs.

Step-by-Step Circuit Diagram and Construction

1. Circuit Diagram

Below is a high-level description of how the circuit works:

  1. Power Supply: Connect the positive terminal of your power supply to the power rail of the breadboard, and the negative terminal to the ground rail.
  2. Transistor Setup: The 2N2222 transistors will act as the main switching components. For each transistor:
    • The collector is connected to the anode side of multiple LEDs (grouped for each transistor).
    • The emitter is connected to ground.
    • The base of each transistor is connected to a biasing resistor (10kΩ) and a capacitor to smooth out the transitions.
  3. LED Setup: The LEDs are divided into three groups, with the first group connected to the collector of the first transistor, the second group to the second transistor, and the third group to the third transistor. The LEDs should have individual current-limiting resistors to prevent damage.
  4. Sequential Timing: Capacitors (typically 100μF to 150μF) are used between the transistors' base to create a time delay in the switching process, allowing the "running" effect of the LEDs as each transistor turns on in sequence.

2. Connecting the LEDs and Resistors

For each LED in the circuit:

  • Connect the anode (positive) terminal of the LED to the collector of the transistor.
  • Connect the cathode (negative) terminal of the LED to the current-limiting resistor (330Ω to 1kΩ), and then to the ground.

3. Base Resistors for Transistors

Each transistor will have its base connected through a 10kΩ resistor. This limits the current flowing into the base, ensuring that the transistor switches properly.

4. Capacitors for Timing Control

The capacitors connected between the base and collector of the transistors control the time delay between each LED lighting up. This creates the sequential lighting or running effect. Larger capacitor values (e.g., 150μF) will slow down the running effect, while smaller values (e.g., 100μF) will speed it up.

How the Circuit Works:

Running led lights circuit diagram


The circuit operates by having one transistor turn on, causing the LEDs connected to it to light up. The timing capacitor delays the signal to the next transistor, allowing the next set of LEDs to light up while turning off the previous ones. This process repeats, creating the illusion of a "running" light.

  • Step 1: Initially, when the circuit is powered on, one transistor receives a signal through the capacitor and switches on, lighting up its corresponding LEDs.
  • Step 2: As the capacitor discharges, the signal is passed to the next transistor, which switches on, lighting up the next set of LEDs.
  • Step 3: This process continues in a loop, cycling through the three transistors, each controlling a set of LEDs. The transition between LEDs creates the running effect.

Final Circuit Design:

The complete circuit consists of three stages, each driven by a 2N2222 transistor, with LEDs grouped and connected in parallel to each transistor's collector. The timing capacitors and base resistors control the switching of transistors, enabling a continuous flow of the running lights effect.

Adjusting the Speed of the Running Lights:

To change the speed at which the LEDs run, simply adjust the values of the capacitors between the transistors' base and ground. Larger values will slow down the effect, while smaller values will speed it up.

Conclusion:

This running LED light circuit using three 2N2222 transistors and 19 LEDs is a fun and straightforward project that gives a dynamic lighting effect. The use of transistors as switches allows for a cascading sequence of lights, while the timing capacitors add control over the speed of the transition. Whether for decorative purposes or simply to learn more about transistors and timing circuits, this project is an excellent way to expand your understanding of electronics.

By experimenting with different capacitor values, you can customize the running speed and create various lighting effects. Happy building!

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