• Skip to main content
  • Skip to primary sidebar

Homemade Circuit Projects

Need circuit help? Post them in the comments! I've answered over 50,000!

Blog | Categories | About | Contact | Calculators-online
You are here: Home / Mini Projects / Single Transistor LED Flasher Circuit
warning message: electricity is dangerous, proceed with caution
OneTransistorLEDFlasherCircuitDiagram2CImage

Single Transistor LED Flasher Circuit

Last Updated on March 9, 2025 by Swagatam 145 Comments

It is possibly the smallest LED flasher to date, which is able to flash an LED ON/OFF infinitely using a single transistor, a resistor, and a capacitor.

Table of Contents
  • How it Works
  • Parts List for the proposed single transistor LED flasher circuit
  • Circuit Diagram
  • Calculating the LED Flashing Frequency
  • To adjust the flashing rate:
  • Connecting an External Transistor for Higher Loads
  • Video Clip:
  • PCB Design

Can you imagine making a great looking LED flasher or blinker with just a single transistor and a couple of other passive parts?

That's exactly what I have explained in this post! This is perhaps the world's simplest and the tiniest LED flasher you can get!

How it Works

I came across this phenomena some eight years ago (2006), accidentally, while trying to make a smallest possible motorcycle side indicator flasher, and was surprised by the phenomenon.

However, then I realized that the phenomenon was already discovered by Mr. Dick Cappels while investigating the negative resistance theory in BJTs by the Japanese researcher Mr. Reona Esaki (Aka Leo).

Reona Esaki's thesis work in the relevant field and on tunnel diodes ultimately won him the Nobel Prize in 1972.

That looks too good to be true, however the following diagram will simply prove that it's really possible to create a working LED flasher circuit using just one general purpose transistor as the main component.

At that time, I was unaware that this was occurring as a result of the transistor's negative resistance characteristics.

The circuit actually exploits the negative resistance factor in transistors to produce the blinking effect.

I'll be soon writing a comprehensive article on this and we'll see there how the concept can be modified in many different ways.

Parts List for the proposed single transistor LED flasher circuit

  • R1 = 2K7,
  • R2 = 100 Ohms,
  • T1 = BC 547,
  • C1 = 100 uF to 470 uF
  • LED = Any Type, any color

The flashing rate could be varied either by changing the value of R1 or C1 or both together. But the supply voltage not be less than 9V otherwise the circuit might fail to work correctly.


You may also love to read this article: Blinking LED Circuit using LDR


Circuit Diagram

LED flasher circuit diagram using single transistor

Calculating the LED Flashing Frequency

You can use the following formula for approximately calculating the LED ON/OFF blinking rate

Frequency (f) ≈ 1 / (2.1 * R * C)

Where:

  • R is the resistance in ohms
  • C is the capacitance in farads

This formula gives us a rough idea of what the flashing frequency might be. But the actual frequency can be affected by a hand full of different factors, for example like the specific components you are using in the circuit, the voltage of the power supply and also the temperature.

To adjust the flashing rate:

  • Increase the resistance (R): If we make the resistance higher, it will take longer for the capacitor to charge up which means the flashing rate will be slowed down.
  • Decrease the capacitance (C): On the opposite side, if we lower the capacitance vaalue, the capacitor will charge up faster causing the flashing rate to speed up.

Connecting an External Transistor for Higher Loads

single transistor high power LED flasher circuit diagram

Video Clip:

PCB Design

single transistor flasher PCB design

You'll also like:

  • 1.  16 Easy IC 741 Op Amp Circuits Explained
  • 2.  Build Simple Transistor Circuits
  • 3.  6 Best Ultrasonic Circuit Projects for Hobbyists and Engineers
  • 4.  How to Make Any Light a Strobe Light Using Just Two Transistors
  • 5.  Simple Circuits using IC 7400 NAND Gates
  • 6.  How to Make a Cheap LED Name Plate with Illuminated Back Light

Filed Under: Mini Projects Tagged With: Flasher, LED, Single, Transistor

About Swagatam

I am an electronics engineer and doing practical hands-on work from more than 15 years now. Building real circuits, testing them and also making PCB layouts by myself. I really love doing all these things like inventing something new, designing electronics and also helping other people like hobby guys who want to make their own cool circuits at home.

And that is the main reason why I started this website homemade-circuits.com, to share different types of circuit ideas..

If you are having any kind of doubt or question related to circuits then just write down your question in the comment box below, I am like always checking, so I guarantee I will reply you for sure!

Previous Post: « Automatic Voltage Stabilizer Circuit for TV sets and Refrigerator
Next Post: How to Calculate Transformerless Power Supply Circuits »
Subscribe
Notify of
guest
guest
145 Comments
Inline Feedbacks
View all comments

Primary Sidebar

circuit simulator image

Subscribe to get New Circuits in your Email

Categories

  • Arduino Projects (90)
  • Audio and Amplifier Projects (132)
  • Automation Projects (17)
  • Automobile Electronics (101)
  • Battery Charger Circuits (84)
  • Datasheets and Components (105)
  • Electronics Theory (140)
  • Free Energy (38)
  • Games and Sports Projects (11)
  • Grid and 3-Phase (19)
  • Health related Projects (25)
  • Home Electrical Circuits (12)
  • Indicator Circuits (15)
  • Inverter Circuits (89)
  • Lamps and Lights (142)
  • Meters and Testers (71)
  • Mini Projects (46)
  • Motor Controller (64)
  • Oscillator Circuits (28)
  • Pets and Pests (15)
  • Power Supply Circuits (89)
  • Remote Control Circuits (50)
  • Security and Alarm (64)
  • Sensors and Detectors (103)
  • SMPS and Converters (31)
  • Solar Controller Circuits (60)
  • Temperature Controllers (42)
  • Timer and Delay Relay (49)
  • Transmitter Circuits (29)
  • Voltage Control and Protection (38)
  • Water Controller (36)

Other Links

  • Privacy Policy
  • Cookie Policy
  • Disclaimer
  • Copyright
  • Videos
  • Sitemap

People also Search

555 Circuits | 741 Circuits | LM324 Circuits | LM338 Circuits | 4017 Circuits | Ultrasonic Projects | SMPS Projects | Christmas Projects | MOSFETs | Radio Circuits | Laser Circuits | PIR Projects |

Social Profiles

  • Twitter
  • YouTube
  • Instagram
  • Pinterest
  • My Facebook-Page
  • Quora
  • Stack Exchange
  • Linkedin
  • Recent Comments

    • Swagatam on Simplest AM Radio Circuit
    • Swagatam on Simple Online UPS Circuit
    • Saroj Sahu on Simple Online UPS Circuit
    • michel van simaeys on Simplest AM Radio Circuit
    • Swagatam on Simplest AM Radio Circuit

    © 2025 · Swagatam Innovations