Today we will learn how to make an LED flashing or LED blinking circuit using only transistors. We will be using two transistors to make this circuit instead of 555 Timer IC because the transistors are cheaper and are easily available in the market.
Hardware Components
The following components are required to make an LED Flashing circuit
| S. NO | Component | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Connecting Wires | – | 1 |
| 3. | Battery | 9v | 1 |
| 4. | Transistors (NPN, PNP) | BC547, 2N3906 | 1,1 |
| 5. | Resistor | 22 ohm, 1K, 1M | 1,1,1 |
| 6. | Capacitor | 2.2uF | 1 |
| 7. | LED | 5mm | 1 |
BC547 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of BC547
2N3906 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3906
LED Flashing circuit
Working Explanation
This circuit works as an astable multivibrator circuit, which we can view on an oscilloscope. Being an astable multivibrator, the state of the circuit is constantly changing and this change affects the flow of current and voltage, which will be visible on the LED.
For this blinking LED circuit to work properly, we simply need some resistors, so that the LED doesn’t get burnt out. To adjust the blinking speed of the LED, change the value of the capacitor and the resistor. The transistors do not necessarily have to be BC547, you may use 2N2222 or similar small-signal transistors, but It is recommended to always use the equivalent transistors.
Application
- Can be used on roads for signaling purposes.
- We can create a dancing LED circuit by combining many similar circuits, which we can use for advertisement boards
