by Michael Simpson
Floating Light Show
Mix Colors and Software for a Neat Effect!
After opening the pool this
year, I decided to
purchase some sort of
lighting system so we could enjoy
those muggy Virginia nights. I
wanted a color system that lit the
water inside the pool. Many
existing lighting systems had 12
V lights that used a transformer
to lower the voltage from 110 V,
but I did not want to chance
something going wrong with one
of these. Plus, the fiber optic systems were much too expensive,
so I decided to break down and build something.
that I have chosen.
The AthenaHS also has a very
small carrier board that will allow
me to build the light very easily.
My requirements were simple:
• It must be powered by four rechargeable AA batteries.
This will give a nominal 4. 8 volts, which eliminates the
need for a voltage regulator.
• It must last at least six hours on a single charge. Longer
would be a plus.
• It must have three colors and cycle slowly between them
to change the mood of the pool.
• It must be self-contained and float on the
surface of the pool, yet it has to shine light on
the pool floor.
• It must fit in a small, waterproof tub.
• It must be easy to build and inexpensive, so that
I can build more than one. I will probably build
four for my pool.
Figure 1 shows the hookup
to the carrier board. We only
need six ports on the AthenaHS
to drive the six LEDs. I decided to
use a 2 x 6 female header, so I
could just plug the LEDs in
place. While this is not the most
rugged connection method, it would allow me to experiment with different colored LEDs.
Figure 2 shows the slightly modified carrier board. You
can also use two 1 x 6 female headers glued or stuck
together with double-sided foam tape. Connect the free
ends of the header together and tie to Vss, as shown in
The carrier comes with some snap connect male
headers and you will only need two of them — one each
connected to the + and – leads, as shown in Figure 2. This
The AA batteries and six hour duration
pretty much dictated some sort of LED light
system. For the multiple colors, I decided to use
blue, red, and green ultra bright LEDs. I wanted
to use 5 V LEDs that pulled less than 25 ma so I
could power them directly from the
microcontroller’s IO port. For more brightness, I
would use two LEDs for each color, each on its
For the microcontroller, I decided on an
AthenaHS for its speed, cost, and simplicity. I
needed to generate six PWM signals for mixing
the colors. The AthenaHS can source or sink 25
ma on each port. This is perfect for the LEDs