Simple Single Transistor LED Flasher Circuit

The smallest LED flasher circuit ever built is shown in this article.

An LED is made to flash constantly ON and OFF with just a transistor, resistor and capacitor.

Imagine using a single transistor and a few other simple components to create an eye catching LED flasher circuit.

This is exactly what one might see constructing.

The simplest single transistor LED flasher circuit is discussed in this article..

What is a Single Transistor LED Flasher Circuit:

The single transistor LED flasher circuit is a simple electronic circuit that uses a single transistor to turn on and off a light emitting diode LED.

Simple in design this kind of circuit is often used as a visual indicator or for decoration.

Circuit Working:

Parts List:

Back in 2006 while trying to make the smallest motorbike flasher possible We discovered this fascinating fact.

It turns out that Dick Cappels once investigated a similar concept based on the work of tunnel diode inventor and Nobel winner Leo Esaki.

The circuit below shows that one can indeed construct a functional LED flasher using just one transistor despite the fact that it may appear impossible.

We were unaware at the time that this thing was caused by a unique negative resistance characteristic of transistors.

This is how the circuit smartly generates the blinking effect.

We will explore this phenomenon and more in a future article along with changes and other uses.

The flashing speed is adjusted by changing the values of the 2.7k resistor or 100µF capacitor or both.

Just remember the voltage needs to stay above 9V for everything to work properly.

Formulas:

Below are the formulas for Simple Single Transistor LED Flasher Circuit:

Resistor in series with LED R1 (100Ω):

To keep the LED from burning out this resistor limits the amount of current that flows through it.

Ohms law is used to find the suitable value for R1:

R₁ = (V_supply – V_f) / I_led

where,

• V_supply is supply voltage for 12V
• V_f is the forward voltage of the LED which is around 1.8V – 2.2V for red LEDs
• I_led is the desired LED current around 15mA – 20mA for standard LEDs

How to Build:

To build a Simple Single Transistor LED Flasher Circuit follow the below mentioned steps:

• Put together the required parts such as a BC547 transistor, 100Ω and 2.7k resistors, a capacitor ranging from 100μF to 470μF and an LED of ones choice.
• As shown in the circuit diagram connect the parts.
• Ensure that the LED, transistor and capacitor are all polarized correctly.
• To get the desired flashing rate experiment with the values of 2.7k and 100µF.
• Do not allow the supply voltage drop below 9V.

Testing:

• Once the circuit is turned ON observe the LEDs blinking.
• Any required adjustments should be made to get the desired result.

Take note:

• With just one transistor it uses a powerful transistor method to get the LED to blink.
• It is a really good way to see how a device is dropped.
• Stay tuned for a complete explanation of how this circuit works.

References:

Design and Build a Simple Analog LED Flasher Circuit

Datasheet Standard LED