ATmega8-POV: Building a Simple Persistence-of-Vision Display

Persistence-of-vision (POV) displays create the illusion of a continuous image by rapidly flashing LEDs in a sequence as they move across a fixed path. This project, ATmega8-POV, showcases how to build a simple POV display using the ATmega8 microcontroller. Designed with the free PCB design software KiCAD, this project offers a fantastic way to dive into microcontroller programming and PCB design.

What is ATmega8-POV?

ATmega8-POV is a project that leverages the concept of persistence of vision, where fast-moving LEDs create an illusion of continuous text or patterns visible to the human eye. The project uses an ATmega8 microcontroller to control a set of LEDs, switching them on and off in a rapid sequence to display patterns or text as the device moves. The PCB for this project was designed in KiCAD, providing an easy-to-replicate circuit layout for hobbyists and engineers.

Project Overview

The project involves several key components and steps, including:

1. ATmega8 Microcontroller: The "brain" of the POV display, which handles the timing and sequence for lighting up the LEDs.
2. LED Array: A series of LEDs controlled by the microcontroller. The LEDs light up in specific patterns that, when moved rapidly, create readable text or images.
3. Power Supply: Typically, a battery powers the ATmega8 and LEDs.
4. PCB Design in KiCAD: This design step involves creating a PCB layout that aligns with the LED positioning and microcontroller connections.

Hardware and Components Required

To build the ATmega8-POV, you’ll need:

• ATmega8 Microcontroller: This microcontroller will handle the LED sequences.
• LEDs (8-12): These will be used to display the POV effect.
• Resistors (typically 220Ω or 330Ω) for current limiting on each LED.
• Capacitors for stabilizing power input to the microcontroller.
• Power Supply: A small battery pack, such as 3V or 5V, to power the board.
• PCB designed in KiCAD or a breadboard for prototyping.

Designing the Circuit in KiCAD

The design process in KiCAD involves several steps:

1. Schematic Design: Draw a schematic with the ATmega8 microcontroller connected to the LED array. Each LED should have a resistor to limit current, and you may add bypass capacitors near the power pins of the microcontroller for stability.
2. PCB Layout: Convert the schematic to a PCB layout. Place the ATmega8 and LEDs on the board in a way that minimizes trace lengths and makes it easy to mount the device for motion.
3. Export and Manufacture: Once the PCB layout is complete, generate the necessary Gerber files, which can be sent to a manufacturer for PCB production.

Programming the ATmega8

The ATmega8 needs to be programmed to light up the LEDs in specific sequences to form patterns or letters. Here's a high-level guide to the code structure:

1. Initialize the ATmega8: Set the data direction register for the LED pins as output.
2. LED Sequence Logic: Create a loop where each LED lights up in a specific order. This sequence could represent letters, numbers, or simple patterns.
3. Timing and Delay: Add delays to control the duration each LED is on, ensuring that patterns are visible when the display is moved at a certain speed.

Mounting and Testing

Once you’ve assembled the components and programmed the ATmega8, the next step is to test the display:

1. Mount the PCB on a structure that allows it to move (e.g., attach to a fan blade or motor arm).
2. Power On: Ensure the power supply is sufficient to keep the LEDs bright.
3. Test and Adjust: Test the timing of the display by moving the PCB. Adjust delays in the code as necessary to improve readability.

Enhancements and Customization

Here are a few ideas to take this project further:

• Variable Text Display: Update the code to allow for different text or patterns to display on each cycle.
• Wireless Control: Integrate a wireless module (like Bluetooth) to change text or patterns in real time.
• Battery Optimization: Add power-saving techniques to extend battery life during operation.

Conclusion

The ATmega8-POV is a fantastic introduction to microcontroller programming and PCB design, allowing creators to explore concepts in timing, LED control, and basic electronics. By designing and building this project, you’ll gain hands-on experience with persistence of vision, an engaging and rewarding display technique. Plus, KiCAD’s user-friendly interface makes it accessible for creating and customizing your PCB layouts.

Give this project a try and enjoy the mesmerizing light show as your ATmega8-powered display brings text and patterns to life!

You can find the PCB Design using KiCAD and additional resources on the project’s GitHub page: