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  • Writer's pictureDan Koellen AI6XG

Wishing You a Very Random Christmas

Being the holiday season I decided to post this article from the December 2014 issue of Nuts & Volts magazine that I wrote about an outdoor Christmas Tree display I built and erect every holiday season. I had built an outdoor tree of light strings in a tree formation but was not pleased with the static display. So I built a microcontroller control box that will change the display in a random manner. At each power up, the seed for the random number generator is changed so that patterns are different for each operation.

I have posted here the article for your viewing pleasure and the C source code in GitHub. From the article and source code you can build your own version. The C program was used with an old compiler so if you compile with the current Microchip 8 bit compiler there will be errors thrown but they should be easily resolved. I also have posted here the original photos used for the article with an additional video of the 'Christmas Tree' in operation.

random xmas direct
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Eight channel light controller schematic

A view of the solid state relay (SSR) board
The microcontroller circuitry is built on a perf board

The microcontroller board mated to the SSR board

A close up view of the AC wiring

The completed assembly before installing the cover

The right figure is a drawing of the 'tree' as viewed from the top, eight sets of LED lights result in 16 legs.

The left figure is a drawing of the side view of the 'tree'. The legs are the LED light strings meeting at

the top of an 8' metal pole.

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