Rainbow QRFlasher: Turn Your QR Code Into a Colorful Light Show!

What if your QR code could shine in all the colors of the rainbow?

With Rainbow QRFlasher, your static black-and-white code transforms into a vibrant, blinking light show—grabbing attention and making scanning easier, more fun, and futuristic!

Rainbow QRFlasher is a simple yet eye-catching project designed to make your QR codes stand out. By using colorful blinking LEDs, the QR code becomes more visible and attractive—perfect for exhibitions, shops, creative displays, or personal DIY projects. With low-cost, easily accessible components, you can build it in just a few steps—even if you're a beginner.

This project brings together functionality and creativity, adding a layer of interactive color to something as common as a QR code.

✨ Features

1. 🌈 Dynamic LED Blinking: Makes your QR code glow, blink, and dance in vivid rainbow colors.
2. 💰 Low Cost: Built with affordable, commonly available components.
3. 🔧 Easy to Assemble: Great for beginners, students, and hobbyists.
4. 🎨 Customizable: Adjust the LED patterns, colors, and QR code design to match your style.

Parts:

1. Small plastic box – (e.g. cheese or food container, ~7×10cm)
2. 2 or more Self-Flashing RGB LEDs – common cathode or anode types
3. Battery holder – for 2×1.5V AA or AAA batteries
4. Wires – thin and flexible for easy soldering
5. Transparent paper – such as:
6. Vellum paper
7. Tracing paper
8. Translucent paper
9. Butter paper (optional)
10. Transparency sheet (acetate sheet) – printable with laser printer
11. Aluminum foil – for inner reflection and light diffusion
12. Printed QR Code – on the transparency sheet

Tools:

1. Soldering iron – for connecting LEDs and wires
2. ✂️ Scissors or precision cutter – for trimming paper and transparency
3. ️ Paint or permanent marker – to cover the box (optional)
4. ️ Laser printer – to print the QR code on the transparency (Don't worry if you don't have one. no need to sell your kidney for it! Just visit a local print shop and they'll do the job for less than a cup of coffee)
5. Glue or glue stick – to attach QR and paper layers
6. Hot glue gun – for securing components inside the box
7. Ruler and pencil – for layout and alignment (optional)

1. Take the plastic box and clean it thoroughly.
2. After cleaning, paint the box with your desired color to give it a neat and polished look. You can choose any color that fits the aesthetic of your project.
3. Cut a square hole measuring approximately 8 cm by 8 cm on the front side of the box. This will be the window where the LEDs will shine through, enhancing the visibility of the QR code. You can use a sharp cutter (X-Acto knife or utility knife) for this step. Be careful and make sure the edges are clean and smooth.

To enhance the reflection of the LEDs and create a more striking effect, we’ll place the LEDs inside a reflector made of cardboard. This reflector will act like a spotlight, amplifying the light and ensuring that the LEDs shine brightly and draw attention to the QR code.

The reflector should be trapezoidal in shape. This specific shape helps in focusing the light from the LEDs in a way that enhances the effect of blinking colors.

Based on the size of the plastic box you’ve chosen, you can create the trapezoidal shape using cardboard. The reflector I’ve created, based on the size of the box, has the following dimensions: the top measures 7 cm by 7 cm, the bottom is 5 cm by 5 cm, and the height of the trapezoidal reflector is around 4.5 cm. These dimensions can be customized depending on the size of your box.

If you want, you can download the template I’ve prepared in PDF format. This template will help you easily

After you have created the trapezoidal reflector, it's important to line the inside with aluminum foil. This will help enhance the reflectivity and direct the light more effectively.

1. Cut a piece of aluminum foil slightly larger than the inner surface of the reflector.
2. Carefully attach the foil to the inside of the reflector using glue or tape, ensuring that the shiny side is facing outward. This will help maximize the light reflection and create a stronger visual effect when the LEDs blink.

This simple step will make your reflector much more efficient in amplifying the light from the LEDs.

In this step, we will wire the LEDs to the power source. You will need at least two Self-Flashing RGB LEDs or more, and they should be connected in parallel. This means that the cathodes (negative terminals) should be connected together, and the anodes (positive terminals) should also be connected together.

1. Connecting the LEDs:
2. Carefully connect the cathodes (the shorter legs) of the LEDs to each other using wire.
3. Similarly, connect the anodes (the longer legs) of the LEDs to each other using wire.
4. The wires should be of an appropriate length—not too short that they can’t reach the reflector, and not too long to avoid clutter inside the box. Ensure that the wires are long enough to connect the LEDs to the battery compartment but not excessively long to create unnecessary space and mess.
5. Connecting to the Battery:
6. The connected cathodes and anodes will be attached to the battery compartment. Make sure you connect the anodes to the positive terminal (+) of the battery and the cathodes to the negative terminal (−).
7. You can also include a switch in the circuit to control the on/off state of the LEDs. This will make it easier to turn the LEDs on and off when needed.
8. Alternatively, you can disconnect the batteries when you want to turn off the LEDs. Simply remove the batteries to stop the LEDs from flashing.
9. Using Different Battery Types:
10. While two 1.5V batteries work well for this project, you can experiment with other types of batteries. Just ensure the voltage is suitable for your LEDs and won’t damage them. You can use either rechargeable or regular batteries, depending on your preference and the desired runtime for the device.

Now that the LEDs are wired and the reflector is lined with aluminum foil, it's time to mount the LEDs into the reflector and secure everything neatly inside the box.

1. Drilling Holes in the Reflector:
2. Create small holes with a diameter of about 5 mm on the surface of the reflector. These holes will hold the LEDs in place.
3. Make sure the holes are not too big—if they are, the LEDs might slip out. At the same time, they should not be too small, or you won’t be able to insert the LEDs properly.
4. The number of holes depends on how many LEDs you are using. Space them evenly to ensure good light distribution.
5. Inserting the LEDs:
6. Carefully insert each LED into its corresponding hole.
7. Make sure the legs of the LEDs pass through the holes without forcing or bending them too much.
8. Securing the LEDs:
9. Use hot glue or any strong adhesive to secure the LEDs to the reflector. Apply the glue around the base of each LED to prevent movement.
10. Ensure that the LEDs are tightly fixed and do not wiggle inside the holes.
11. Avoiding Short Circuits:
12. Be cautious that the LED wires do not touch the aluminum foil lining inside the reflector, as this could cause a short circuit.
13. You can use electrical tape to cover exposed parts of the wires if necessary.
14. Mounting the Reflector to the Box:
15. Once the LEDs are secured, attach the entire reflector to the inside of the plastic box using glue.
16. Position it carefully so that the light shines directly through the square window you cut earlier.
17. Organizing the Wires:
18. Neatly organize the wires inside the box. Use small cable ties or tape if needed to keep them from tangling.
19. Make sure the wires are positioned in a way that does not block the light from the LEDs.
20. Placing the Battery Holder:
21. Finally, place the battery holder inside the box in a convenient location. It should be easy to access if you need to replace the batteries.
22. You can use double-sided tape or hot glue to secure it in place.
23. Adding Diffusion (Optional but Recommended)
24. To improve light diffusion and create a softer glow, you can place a thin layer of polyester fiberfill (commonly used in pillows and stuffed toys) inside the reflector.
25. This helps scatter the light evenly and hides the individual LEDs, so only the glow is visible.
26. Make sure not to block too much light—use just enough fiberfill to cover the LEDs lightly.

To make the device look more attractive and well-finished, you can cover the lid of the box with a custom-made decorative cover. This cover not only improves the appearance but also helps diffuse the light from the LEDs for a more eye-catching effect.

1. Preparing the Cover:
2. Cut a piece of thick paper or cardstock to match the dimensions of the box lid.
3. Create a square cutout in the cover that aligns with the square hole you made on the lid in Step 1.
4. The square cutout on the cover should be slightly smaller than the one on the box lid. This will help concentrate the light for a sharper look.
5. Download the Template (Optional):
6. I have prepared a ready-made template for the cover design that you can download in PDF format.
7. If you prefer, you can also design your own cover based on the size and style of your box.
8. Adding a Diffuser:
9. To make the LED light spread more evenly and look softer, you can place a piece of Vellum Paper or Tracing Paper behind the square cutout on the cover.
10. Simply cut the translucent paper to the right size and glue or tape it behind the square opening. This will diffuse the LED light beautifully.
11. Protecting the Cover:
12. To keep the cover clean and free from stains, you can apply transparent tape or clear adhesive film over the entire surface. This also helps prevent scratches during use.
13. Attaching the Cover to the Box Lid:
14. Finally, attach the finished cover to the lid of the box using double-sided tape or glue.
15. Make sure it is properly aligned with the hole in the box so the LED light shines through perfectly.

One of the key features of the QRFlasher device is its eye-catching QR code, which becomes even more noticeable with the LED flashing effect. Here’s how to create and place it:

1. Generating the QR Code:
2. To generate the QR code, you can use various online QR code generators such as QR Code Generator, QRCode Monkey, or mobile apps that support QR creation.
3. Enter the URL of your Instagram page (or any link you want to share) and generate the QR code.
4. Make sure the generated QR code is clear and not overly complicated for easy scanning.
5. Printing the QR Code:
6. After generating the QR code, print it on transparent paper (such as clear sticker paper or transparency film) to allow the light to pass through easily.
7. The size of the QR code should match the square cutout on the cover created in Step 5. Adjust the size before printing to ensure a proper fit.
8. Cutting and Trimming:
9. Carefully cut out the printed QR code, making sure the edges are clean and straight.
10. If you printed it on transparency film, you might need to use scissors or a sharp blade for precise cutting.
11. Placing the QR Code on the Cover:
12. Attach the QR code to the inside of the square cutout on the decorative cover.
13. You can use clear adhesive to secure it firmly.
14. Make sure it is perfectly aligned so that the LED light shines through and makes it more noticeable.

Depending on how you plan to use your QRFlasher, you might want to hang it from a surface like a wall, a shelf, or even a backpack. In such cases, adding a simple handle or hanging bracket can make it more convenient to mount or carry.

This feature is completely optional and may not be needed for all use cases.

You can make the handle out of any material you have on hand — plastic, metal, wood, or even a sturdy piece of wire. I used a small metal strip, bent into shape and attached to the main body of the QRFlasher using screws. It works well for hanging the device or securing it with a hook or string.

Here are some shots of the completed Rainbow QRFlasher in action.

The colorful LEDs light up the QR code beautifully, making it eye-catching and fun.

Whether you're showing it off at an event or placing it on your desk, it's sure to grab attention!

If you build your own Rainbow QRFlasher, I'd love to see it! Share your version in the comments.