Posted in Projects, Software Libraries, Tutorials by Bill
21 Dec 2010
Nothing means more to someone then a gift that took more time to make than money to buy. This is an example of such a gift. Set your way-back-when machines to 2002. Getting ready to finish high school, I had built up some hacker level of electronic knowledge. My parents; both nautical people; have a large lighthouse fountain in their backyard. My mother’s only wish for Christmas that year was for me to build something that would illuminate the lighthouse as if it were a functioning beacon. I obliged, with a circuit consisting of a 555 timer and a 4017 decade counter. It resulted in a simple device that did the job.
Not actual fountain, but close
The old LED board
Fast forward 8 years. I’m out of college with an EE degree working for the US Navy building robots. My mother’s wish this year? To replace the aging and failing lighthouse circuit. Well, I can’t just resort to cheap protoboard again. I wanted to show here all that money for college was well spent.
Enter the LED Lighthouse Keeper. A day’s worth of design and programming, with (hopefully) impressive results.
The new design
The design is simple. Four groups of Red/White LED pairs (the lighthouse has four windows at the top), a super-bright blue LED to illuminate the lower windows, a LED driver circuit and an ATtiny85 to create a realistic circulating fade effect. The LED driver is for the Luxeon Rebel LED, which can draw a few Watts!!
Schematic (Click for full)
Not the most elegant solution to everyone I’m sure, but for the few bucks an ATtiny costs, it got the job done. I did run into some issues with glitches in hardware generated PWM, but I wrote a Band-Aid fix. I could have just done software PWM, because the ATtiny85 isn’t doing anything else (like monitoring electrical mains) but in the end I just finished what I had started with hardware.
The PCB had to be carefully designed to dissipate heat away from the blue LED. If you look at the picture below, you can see the polygon in the middle whose sole purpose is to draw heat away from the LED.
UPDATED: A video of it installed
Now here’s the kicker. How to present such a gift? I thought it would be cool to create my own DIY cheesy retail packaging as well, demo button and all. I enlisted the help of my talented girlfriend to design the graphics, and she did a great job. I added a demo circuit, which is just a pushbutton switch and a 9V battery, but the effect is awesome. This really does look like something you would pick up at a store, yet is a custom made gift. I hope she likes it.
The source code is available for Download Here.
Some more photos. All photos can be enlarged by clicking on them.
Printed out the design, created in PhotoShop
Gluing design to box. We also cut out a hole, and glued clear plastic on the demo window from inside.
Demo circuit with 9V battery
Added some padding on the inside
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