Re: Solar Powered PIC
- From: Jonathan Kirwan <jkirwan@xxxxxxxxxxxxxx>
- Date: Sat, 24 Jun 2006 18:28:24 GMT
On Tue, 20 Jun 2006 00:27:56 +0100, WiseOne <someone@xxxxxxxxx> wrote:
I'm Just gathering thoughts together for a project that has family
connection close at heart.
My father (deceased) was a lighhouse keeper on various lighhouses
around Ireland and as one of those Father/Son things, I'd like to keep
remembering him by having something around my home that may seem
unusual to neighbours but meaningful to me plus, a conversation
starter.
I used to have a lighhouse overlooking a garden pond that was powered
by a simple stobe circuit but it was more of a novelty when my dad was
alive.
What I would like to do now as a project is to build a PIC based
project that will simulate the flashing sequence of a particular
lighthouse. The PIC circuit I can get working okay via they
technology department in the school I work in but what I would like to
do is operate it using a solar panel so that I don't need to work with
mains - everything self-contained.
I've been looking at the Garden type solar panels and notice that they
only charge at 3.6V into 2 NICAD batteries at 2.8V but PIC's operate
at 5V. I would like to use LED's as the light source so what way
would anyone suggest I increase the charging mechanism so that I can
build up a suitable voltage/current to operate a PIC circuit with
LED's (say 1 bright LED)
A couple of critical things:
(1) Power source. I gather from this that you are considering using
what you've found for garden solar panels. Just to add to what you
mention above, I just purchased a box of 15 garden walkway lamps from
Costco which also include a solar panel for each one, 2 rechargeable
AA batteries in each one (I assume 1.2V each, for a total of 2.4V),
and several bright LEDs for the lighting. Cost was $6 each, complete.
In my case, I think the voltage is 2.4V or so, so I agree with your
low voltage desire for your power source. Seems about what the market
place is doing right now. So less than 5V, for sure.
(2) LED choice and drive. You don't say exactly how you want to
simulate the flashing sequence. I'm not sure whether you are
considering a special, recognizable form of ON/OFF or if you actually
plan to include a rotating platform (out here, some lighthouses use a
rotating system at a recognizable rate) and instead keep the LED on
all the time. My own preference for something like this would be to
avoid the rotation and instead control the light -- less complexity
and almost certainly lower power consumption.
The above two items are going to be your critical factors for self
powering. You will need a power source that provides _more_ Joules
per daylight day than your lighting requires per 24 hours. If you
fundamentally screw this up and set yourself an LED lighting system
that will consume more than your solar system can provide, it's all
over and you will have to provide a different power source.
So think carefully about your LED lighting rate and the power it will
require (ignore the voltage drive required, for now, as that is an
easily solvable problem, regardless.) Which LED and what is the peak
operating voltage and current for it? How long will it be on? Are
you planning on ramping up (and down) the brightness over a
significant period of time? If so, how long is that? And how long
between these cycles? How many of these LEDs would you consider using
for the "light"? With that, one can compute the total number of
Joules required to operate them each day/night.
Also, think carefully about your ambient sunlight in your area and the
total number of effective hours you will get in your system on the
worst case day of the year. Or else, you will need a storage system
(batteries) that can hold a charge for extended periods if you plan on
capitalizing on the extra energy captured in the summer to partially
power it in the winter. Any way you decide to look at this, you must
find that the solar power available with some system you are
considering is enough to handle the average requirements of your LEDs
and, more likely, on the worst day of the year can supply enough power
to last through the night and wee daylight times.
If you find that whatever power source you want to use will more than
meet the needs of your LED "lighthouse", then I think the rest can be
worked out. If you need higher voltage for your LEDs, it's not hard
and it's not expensive to work out an efficient means to convert lower
voltage to higher voltage. Even if you chose to use a flashlamp with
a 300V voltage and a 4kV trigger volt pulse to fire it you could do
that with just the 2.4V I was talking about on my own units. So it's
not so much about those difficulties as it is about making sure that
you can reasonably gather enough solar power for your lighthouse.
So get those parts right and the rest can somehow follow, I think.
And if you get all this working out well enough, quite frankly you may
have a good product to sell to a select group of potential buyers.
Their small market may allow you to target your advertising at low
cost, with high yield -- enough to operate a small and enjoyable
business, anyway. Consider the thought. Later on, you can broaden
that out, if it pleases you to work out the manufacturing and cost
issues adequately in order to build in enough margin for general
resellers.
Jon
.
- References:
- Solar Powered PIC
- From: WiseOne
- Solar Powered PIC
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