This article unveils what might be the tiniest LED flasher ever built.
It uses just one transistor, a resistor and a capacitor to make an LED blink on and off forever.
Imagine creating a cool LED flasher with only a single transistor and a few other basic parts.
That is exactly what we are building here.
Get ready to witness the worlds simplest single transistor LED flasher circuit.
What is a Single Transistor LED Flasher Circuit:
A single transistor LED flasher circuit is a basic electronic circuit that flashes a light emitting diode LED on and off using a single transistor.
This type of circuit is very basic and is often used for decorative purposes or as a visual indicator.
How it Works:
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 |
Back in 2006, while trying to design the smallest possible motorcycle flasher I, stumbled upon this cool discovery.
It turns out a similar idea was already explored by Dick Cappels based on the work of Nobel laureate Leo Esaki (famous for tunnel diodes).
Though it might seem unbelievable the circuit below proves you can indeed build, a working LED flasher with just one transistor.
At the time I did not realize this effect came from a special negative resistance property in transistors.
The circuit cleverly uses this to create the blinking effect.
We will explore this phenomenon and more in a future article, along with tweaks and other uses.
The flashing speed can be 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:
Resistor in series with LED R1 (100Ω): To keep the LED from burning out, this resistor restricts the amount of current that flows through it.
Ohms law may be utilized to ascertain the suitable value for R1:
R1 = (Vsupply – Vf) / Iled
where,
- Vsupply: Supply voltage 12V
- Vf: Forward voltage of the LED typically around 1.8V – 2.2V for red LEDs
- Iled: Desired LED current around 15mA – 20mA for typical LEDs
Construction Details
- Assemble the necessary components including a BC547 transistor, resistors 2.7k and 100Ω a capacitor 100μF to 470μF, and an LED of your choice.
- Connect the components as per the provided schematic.
- Ensure proper polarity for the transistor, capacitor, and LED.
- Experiment with the values of 2.7k and 100µF to achieve the desired flashing rate.
- Note that the supply voltage should not fall below 9V.
- Apply power to the circuit and observe the LEDs blinking effect.
- Make any necessary adjustments to meet the desired performance.
Note:
- It uses a clever trick with transistors to make the LED blink all with just one transistor.
- It is a great way to see how electronics can be miniaturized.
- Stay tuned for a deep dive into how this works.