Solar Powered PIC

There are PICs that will run on 3.6V.

I believe there are all sorts of 3 volt PIC's available these days.

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Many thanks,

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Here's an option; you'd need to add a solar power source.

A lot of PIC's will run nicely on 2.0 volts if you limit the clock to

4Mhz. Although your solar panel may be 3.6 volts, the pair of NICAD's only puts out 2.4 volts. This is fine for the PIC, but make sure your selected LED's can run on this voltage.

Also, you can safely drive the LED's directly with the PIC, the outputs are current limited.

For lots of PIC stuff:

Luhan

16LF628 is a good choice.

Cheers Folks..

All have given me something to work on.

Many thanks

Declan

Use a TI MSP430 member. It is ultra-low power (sub mA) and will run from very low voltages. For accurate timing you can add a wrist-watch crystal, but even that might be overkill.

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On Tue, 20 Jun 2006 21:23:46 +0100, WiseOne unwisely top-posted:

Do you already have the PIC development system? Frankly, that sounds like overkill for a project that could be done with a CMOS 555 or two or three, depending on your pattern. If you want it to flash Morse Code or something, then it will need to be a little more sophisticated - I did an "SOS" flasher once using logic that I'd lifted from Don Lancaster's TTL cookbook, although I used CMOS. I learned too late that the RS IRF510 doesn't saturate at +6V Vgs. )-; (the "krypton bulb" was too dim, and the MOSFET got _way_ too hot. This was before "logic FETs" had hit the streets.)

Each lighthouse has it own characteristic flash so that mariners can 'hopefully' easily identify it thus give them an indication of their position.

There probably is an easier way but I though that this way would be easier.

Declan

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