John W. Cornwell Home

Spinning LED Display

I designed and built this display for my final project in ECE154, my embedded systems class. It has an array of LEDs attached to a rotating arm that spins at approximately 1000RPM. The device has an infrared eye which triggers the arm to display the image at the same location every time.

Initially, I wanted the device to be able to display a wide variety of colors by lighting the LED's with varying duty cycles to get different intensities. Unfortunately, because of time constraints and the fact that I couldn't find super-bright green LEDs, I ended up with four colors, red, blue, green, and purple.

The actual image is stored in flash memory on my device with 27 bits of information for every "row" in the image (9 pixels in a row, and 3 colors). Instead of writing the image out by hand, I wrote a C++ program to take a 9 pixel high bitmap file and convert it into code I could cut and paste into the microcontroller memory. This way my device does not just display text, it will display anything you can draw in paint.

View of the device:

The LED array:

Text displayed:

An image I drew in paint:

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