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Rojony Khatun
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Last updated: September 22, 2025

Running LED Chaser Light Circuit Using BC547 Transistors

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BC547 Transistor

BC547 Transistor

General-purpose NPN bipolar junction transistor (BJT)

100µF Capacitor

100µF Capacitor

Medium-value film or ceramic capacitor for AC/DC circuits

3V LED 5mm

3V LED 5mm

3V, 5mm round light-emitting diode

10K Fixed Resistor 1/4W

10K Fixed Resistor 1/4W

A 10,000-ohm resistor rated for 0.25 watts

[10k-fixed-resistor-1/4w]
470 ohm Fixed Resistor 1/4W

470 ohm Fixed Resistor 1/4W

A 470-ohm resistor rated for 0.25 watts

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Running LED Chaser Light

Build a running LED chaser light using BC547 transistors. Create sequential LED effects for decorations, indicators, or DIY electronics projects easily.

running LED light DIY

In a running loop, a chaser light with BC547 lights up the lights one after another. The transistors BC547 make LEDs light up and light down in rotation, generating a beautiful chasing effect.

simple LED sequence circuit

The Running LED Chaser Light with BC547 is a famous electronics project, which illuminates LEDs in a sequence to produce a chasing effect. Each of the LEDs would be controlled by a switch (BC547 transistor) to produce timing delays, usually using capacitors and resistors. The circuit is ideal for hobbyists, students, and DIY electronics enthusiasts who would like to develop an understanding of transistor switching, timing circuits, and sequential control. It can be supplied at low-voltage DC and will be safe, and is therefore suitable for breadboard assembly or in small PCB applications. The LEDs can be changed in accordance with your design needs. The effect of running LEDs would best be used in ornamental lighting, or indicators, or in learning practical electronics ideas. The selection of resistors and capacitors is good to provide stable operation and a steady speed of LED chasing.

Work / Installation (Inputs → Outputs)

  • Power Supply → 5–12V DC for safe operation.
  • Timing Components → Capacitors and resistors control LED sequence speed.
  • BC547 Transistors → Act as switches to turn LEDs on and off sequentially.
  • LEDs → Connect in series with transistors and resistors.
  • Installation → Assemble on breadboard or PCB, connect LEDs, resistors, capacitors, and transistors, then power the circuit to see running effect.

Testing & Final Adjustments

Once it is assembled, power the circuit and note the sequence of LEDs. Modulate the speed of the LED chase by changing the values of the resistor or the capacitor. Always be sure that all the transistors of type BC547 are positioned properly (collector, base, emitter). Experiments: Add and remove stages to experiment with the number of LEDs to have and keep current limiting resistors. When it is properly tested, it will operate in a smooth manner in sequence without flickering or skipping. In cases of permanent construction, mounting parts on the PCB are to be used, and a heatsink may be required in case of prolonged operation. This is a good project to read about sequential control of transistors, timing circuits, and the use of LEDs in hobby electronics.

Frequently Asked Questions - Running LED Chaser Light:

What is a running LED chaser?

A circuit that lights LEDs sequentially in a looping pattern.

Which transistor is used?

BC547 NPN transistors act as switches for each LED.

Voltage required?

5–12V DC low-voltage power supply.

Can I change the speed?

Yes, by adjusting resistor or capacitor values.

How many LEDs can I use?

Depends on the design; ensure proper current limiting.

Is it beginner-friendly?

Yes, simple assembly on breadboard or PCB.

Applications?

Decorative lights, indicators, hobby projects.

Do I need resistors?

Yes, to limit current to each LED and transistor.

Can it run continuously?

Yes, ensure components are rated for continuous operation.

Can I expand stages?

Yes, add more transistor-LED stages for longer sequences.

Rojony Khatun

Rojony Khatun

CalculatorToolsProject

Rojony Khatun is the creator of a free online tools website designed to simplify everyday and engineering-related calculations for students, professionals, and hobbyists. The platform offers a wide variety of basic and advanced calculators across key categories, including Electrical Calculators, Electronic Calculators, and Time & Date Calculators, helping users solve problems quickly and accurately.