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Floating Light Show
As seen in
September Nuts n Volts
by Michael Simpson
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 pool
inside the water. Many existing lighting systems had 12v lights
that used a transformer to lower the voltage from 110v 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.
My requirements were simple.
- Must
be powered by 4 rechargeable AA batteries. This will give a
nominal 4.8 volts which eliminates the need for a voltage
regulator.
- Must
last at least 6 hours on a single charge; longer would be a
plus.
- Must
have 3 colors and cycle slowly between them to change the mood
of the pool.
- Must
be self-contained and float on the surface of the pool, yet it
has to shine light on the pool floor.
- Must
fit in a small waterproof tub.
- Must
be easy to build and inexpensive so I could build more than
one. I will probably build 4 for my pool.
The AA batteries and 6 hour duration pretty
much dictated some sort of LED light system. For the multiple
colors I decided to use a blue, red and green ultra bright LED’s
I wanted to use 5v LED’s that pulled less than 25ma so I could
power them directly from the microcontroller IO port. For more
brightness I would use 2 LED’s for each color. each on its own
port.
For the microcontroller I decided on an
AthenaHS for its speed, cost, and simplicity. I needed to
generate 6 PWM signals for mixing the colors. The AthenaHS can
source or sync 25ma on each port. This is perfect for the LED’s
that I have chosen.
The AthenaHS also has a very small carrier
board that will allow us to build the light very easily.
The Circuit
Schematic 1
We only need 6 ports on the AthenaHS to drive the
6 LED’s I decided to use a 2x6 female header so I could just plug the
LED’s in place. While this is not the most rugged connection method
it would allow me to experiment with different colored LED’s.
Figure 1
Figure 1 shows the slightly modified carrier
board. You can also use two 1x6 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 Figure 2.
Figure 2
The Carrier comes with some snap able male
headers and you will only need two of them connected to the + and
– leads as shown in Figure 1. This male header will be used to
connect the batteries, female header. Other than the headers, the
carrier board is built step by step according to the
instructions. When using the AthenaHS with the carrier board you
will need a 20Mhz resonator.
Figure 3
Once the LED’s have been inserted you can
slightly bend the LED’s into groups as shown in Figure 3. The
Short LED lead connects to the outside header (vss). If you are
worried about the leads touching, you can use some 1/16 heat
shrink for insulation. You only need to insulate the IO port side
of the LED.
Update 8/27/2004
Figure 3b
We have added a 5 pin female program header.
(see figure 3b) This will allow us to program the Athena HS
while the LED's are in place. You can snap off a 5
piece section for this header from the 36 pin header recommended
below. It's a tight fit with the Resonator and the header
will be at a slight angle but will work just fine. To make
your job easier position both the header and resonator before
soldering.
Figure 4
Use double sided foam tape to attach the
circuit board to the battery holder. The LED’s should be
centered on the battery holder as shown in Figure 4. To turn on
the light, slip the battery header over the 2 pin header on the
board. The negative side of the battery is connected to the
header pin closest to the LED’s.
The Program (download
it here)
The program must generate 6 PWM signals on
ports 0-5. Three counter variables called bluecount, redcount
and greencount to set the duty cycle of the corresponding colors.
The color pattern is set in the main loop.
We start with red and green turned on and proceed as follows:
-
Fade out red
-
Fade in blue
-
Fade out green
-
Fade in red
-
Fade out blue
-
Fade in green
-
Start over
This pattern assures that all 2 LED color
combos are met. It also means no more than 4 LED’s are on at once
which will go a long way in reducing power consumption.
The actual call to the pwm routine is what
lights the LED’s. At the start of this routine we retrieve a
random number to set the number of times we will actually cycle
through the pwm counts. The more times we cycle the longer it
will take a particular color to fade in or out.
AthenaHS
dim
bluecount,redcount,greencount
dim
curcount,cycle,rnd
'LED Ports
const portblue1 0
const portred1 1
const portgreen1 2
const portblue2 3
const portred2 4
const portgreen2 5
const maxcount 150 'Sets up the PWM frequency and resolution
setio 0,1,2,3,4,5
'Start Point for lights
bluecount = 1
redcount = 150
greencount = 150
loop:
gosub Red_Down
gosub Blue_Up
gosub Green_Down
gosub Red_Up
gosub Blue_Down
gosub Green_Up
goto loop
'------------------------------------
Blue_Up:
'------------------------------------
for
bluecount = 1 to maxcount
gosub pwm
next
return
'------------------------------------
Blue_Down:
'------------------------------------
for
bluecount = maxcount to 1 step -1
gosub pwm
next
return
'------------------------------------
Red_Up:
'------------------------------------
for
redcount = 1 to maxcount
gosub pwm
next
return
'------------------------------------
Red_Down:
'------------------------------------
for
redcount = maxcount to 1 step -1
gosub pwm
next
return
'------------------------------------
Green_Up:
'------------------------------------
for
greencount = 1 to maxcount
gosub pwm
next
return
'------------------------------------
Green_Down:
'------------------------------------
for
greencount = maxcount to 1 step -1
gosub pwm
next
return
'-----------------------------------------
' Generate the light
'-----------------------------------------
pwm:
random 40,rnd 'This will determine how long we stay with a color
rnd
= rnd + 5 'With a minimum of 5 counts
'To
create the 6 PWM signals we turn all ports on then turn them off
'
as each color count is reached.
for
cycle = 1 to rnd
configio 0,1,2,3,4,5
for curcount = 1 to maxcount
if curcount = bluecount then
gosub offblue
endif
if curcount = redcount then
gosub offred
endif
if curcount = greencount then
gosub offgreen
endif
next
next
return
'You
may want to place this code directly in the if statements
'
The KRcompression technology built into the Athena engine
' is
centered around modular code so this particualr way
' is
more efficiant than single if statements
'Port
Handlers
offblue:
input portblue2
input portblue1
return
offred:
input portred1
input portred2
return
offgreen:
input portgreen1
input portgreen2
return
Tub Construction
The actual tub construction is very simple.
Using a Rubbermaid #5193 tub, simply set the
battery and circuit board assembly into the tub with the LED’s facing
up as shown in Figure 5. This is a 1 pint container and the battery
holder centers pretty well without much effort. If you use a
different sized tub or battery layout you will have to make sure the
assembly is centered so that the tub does not tilt to one side.
Figure 5
In
order for the lights to light the pool bottom you need to reflect the
LED’s downward. I have used several reflectors such as compact
mirrors or convex mirrors. Out of all the tests, aluminum foil seems
to work the best at reflecting the light because all the little
crinkles tend to mix the colors more evenly. You can use double sided
foam or tape to attach the foil to the inside of the lid. Make sure
the shiny side is down as shown in
Figure 6
That pretty much is it for the tub construction.
You can add some flowers or a rubber Ducky to the top of the tub if
you wish.
How well does it work?
My wife loves them and cant wait for the long,
hot days of summer. My hard to impress daughter has requested the
five units I made for her next pool party.
I’m getting over 12 hours of use out of the
lights, so my next step is to add a small solar cell to charge the
batteries during the day.
Parts
Updated 8/27/2004
Easy RS232 Driver
Used to program the AthenaHS
AthenaHS
20Mhz Resonator
Athena Carrier 1
36 pin Female Header
4 Cell AA Battery
Holder
9 Pin Cable
Athena Software Free
Download
Plastic Tub Rubbermaid # 5193
Ultra Bright LED’s
-
Blue LED All Electronics
#LED-74
-
Red LED All Electronics
#LED-94
-
Green LED All Electronics #LED-57
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