The smallest LED flasher circuit ever built is the one shown in this article.
To make an LED blink on and off constantly all you need is transistor, a resistor and a capacitor.
Imagine using just a single transistor and a few other simple components to construct a stylish LED flasher circuit.
This is exactly what one can think to construct.
So get ready to see the simplest single transistor LED flasher circuit in this tutorial.
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:
| Type | Specification | Quantity |
|---|---|---|
| Resistors | 2.7k | 1 |
| 100Ω | 1 | |
| Capacitor | 100µF 25V | 1 |
| Semiconductors | Transistor BC547 | 1 |
| LED | Any type any color | 1 |
I came over this interesting finding back in 2006 when attempting to create the tiniest motorcycle flasher imaginable.
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 demonstrates that you can indeed construct a functional LED flasher using just one transistor despite the fact that it may appear impossible.
I was unaware at the time that this phenomenon 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 = (Vsupply – Vf) / Iled
where,
- Vsupply is supply voltage for 12V
- Vf is the forward voltage of the LED which is around 1.8V – 2.2V for red LEDs
- Iled 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 your choice.
- As shown in the 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.
- Turn on the circuit and watch as the LEDs begin to blink.
- To achieve the desired result make any necessary modifications.
Note:
- It makes the LED blink using an effective transistor trick that only requires one transistor.
- It is an excellent method to observe how the device is dropped.
- For a detailed explanation of how this circuit operates stay tuned.