Arduino project · LEDs and lights · Beginner
LED Flasher Light
Two LEDs flash one after the other like an emergency light bar.
What you will learn
- How digitalWrite() switches a pin HIGH or LOW
- How delay() sets the speed of a flash
- Why every LED needs its own resistor
How it works
The Arduino repeats its steps forever. In the first step the red LED is ON and the white LED is OFF for 150 milliseconds. Then they swap. Because the swap happens many times per second, your eyes see a lively flashing light.
Try this next
- Change 150 ms to 50 ms and watch it go faster.
- Add a third LED to the pattern.
- Make one flash longer than the other.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
Parts: sensors and actuators (tap to show or hide)
Try the inputs (virtual sensors)
Pins (you can change them)
| Part | Arduino pin (change it here) | How to wire it |
|---|
Every wire, one by one
Red rail = 5 V from the Arduino 5V pin. Black rail = GND. The coloured wires carry signals. Match the wire colours on the drawing to this list.
| # | Colour | From (part and leg) | To |
|---|
Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.
Quantities come from the parts you added. The store links open a search for that item on Robu.in, Amazon.in and ThinkRobotics, so you always see what is in stock today. Check the model, voltage and price before you order.
| # | Item | Qty | Search term | Buy / compare |
|---|
The PDF has the circuit sketch, pin table, every wire, sequence, full code, the parts list with store links, do’s and don’ts for each part, and the safety notes. The project file lets you come back and keep editing.
In the real world
An emergency light bar
The two LEDs flash one after the other like the lights on a police car.
Tip: use the gold tab at the bottom of the circuit drawing to pull the real-world view up over the Arduino board. Your parts stay visible above it, so you can press a button and watch the real scene react.
- Red LED = the red lamp
- White LED = the blue-white lamp