Circuit help

[ajmix2]

Hello everybody,


I would like to start by saying thanks for all of the help in the other questions. I'm going to replace a retaining wall in my driveway. I'm planning on putting in a lighting system. To do so i would like to design my own system to get some experience designing. I was thinking on using a photo-resistor to control the current flow (12vdc?) to the lights. I was also thinking on using a solar panel like this: http://www.solarhome.org/index.asp?PageAction=VIEWPROD&ProdID=2471 to charge the bettery(ies) during the day. Any suggestions on a schematic idea would help. I'll see if i can design one and post it.

Thank You.

 

[Nigel Goodwin]

I would suggest you seriously look how much light you want from your lights, and how much power they will require - then see how big a solar panel you require (it's likely to be many times more than the one you linked to!). Don't forget, the rated specification of the panel is highly exaggerated.

 

[ajmix2]

What difference would it make if i used LEDs? What kind would i use?

 

[audioguru]

The brightest LEDs available have as much light as a small light bulb.
They would be fine along both sides of a narrow driveway.
It would cost a fortune to solar charge a battery for them.

 

[ajmix2]

I was actually thinking of using 9 LEDs per light. The driveway is 90 feet long, and I figure one fixture (each one has 9 LEDs) every ten feet. As far as charging, would an ultracapicitor be any different? I know these are expensive, but would it be worth my time? Also I'll look into getting a different panel. Any reccomendations?

 

[audioguru]

An ultra-capacitor has nowhere near the capacity of a battery.
9 ordinary LEDs won't light anything at night. You would see the light but not what they shine on. 9 Luxion LEDs would light the driveway. Their voltage is about 3.6V plus some for the current-limiting circuit and their total current is 5.4A. Two Luxion LEDs can be connected in series then the total current is 2.7A. 6 hours of light requires a battery that is rated for 32Ah or more and a huge solar panel to charge it.

My solar garden lights shine brightly all night long in summer. Now when they aren't covered with snow after a sunny day they shine dimly for 1 hour. after a cloudy day they don't light. A huge difference between summer and winter.

Your LEDs will need to be wired together anyway so why not power them from an AC-DC power supply?

 

[ajmix2]

The whole point is a money saver while providing light. Right now we pay a lot for electricity, and in about a couple months, that's going up fifty percent. So to counter this, we are trying to use alternative energy sources. In the near future, we are planning to put up a windmill to help with house electricity. But, the reason I went solar is so I wouldn't have to use the house electricity. And also, so i could get some experience designing, and setting up systems like this. What size solar panel would you recommend? Eventually, we are planning to be totally independent from the grid. But, due to money issues, we can't rush into it. So one thing after another. I also don't think this is going to be cheap.

 

[Nigel Goodwin]

Like I said before, first find how much light output you need, then measure how much power you need for them.

 

[audioguru]

If you live in the Sahara desert which is on the equator, the sun is always nearly straight up at noon and daylight is always very long. There are no trees to make shadows.

You need a solar panel to produce 16Ah per day. The sun is at its highest for only 1 hour per day then the current is lower for the rest of the day. Sunshine in the Sahara desert is for about 11 hours per day. So you need a solar panel rated for maybe 4A/h.

You figure it out for your location away from the equator, if you have trees making shadows, if it is cloudy and in winter when the days are short.