Solar panel/led

Sure it is. Now if you don't find that answer, by itself, particularly helpful, you may want to stop and think about what additional information you might have wanted to include in your question...

Bob M.

Keeping it simple, I want a "shed light" that operates during the day. They seem to consist of a 12v led spotlight and a 5 watt solar panel but most I've seen for sale don't have detailed specs. These would be fine except I don't want to store the power

Well, this question might seem somewhat off-the-wall, but, just to satisfy my curiosity, why do you need lights when the sun is shining?

Thanks, Rich

Aren't you really confusing things? I don't know what "shed lights" are, but the reason those garden LED lights have rechargeable batteries is because the sun is out in the day, but you don't need the light then. At night, you want the light, but there is no sun to power the LEDs.

So you use the sun in the daytime to charge up the batteries, so the power will be available when the sun isn't.

Michael

If you only need the light in the daytime, wouldn't a small skylight or window give you a lot more light for no more money?

Sounds like your shed is as dingy inside as mine! Others have suggested a skylight, but that assumes that one skylight will give enough light, where you need it. The LED approach allows the possibility that you can move it around to different areas as needed.

The advantage of having the battery is not just at night. Since the sun comes and goes behind clouds, the LED brightness would fluctuate without a battery reservoir.

LED brightness is controlled by the current through them, while the voltage across the LED is nearly constant. Without some sort of current limiter, a tiny increase in voltage could cause a whopping big increase in current and blow the LED.

So normally the LED is driven through a resistor or a special current supply... almost *never* straight from a voltage source, unless it is something with an intrinsic current limit. Your solar cells may or may not fall into that category. My guess is that you can probably come up with such a system, but you might have to test a bunch of cells and LEDs first.

So, it's probably simplest to use the resistor or current limiter right from the start. Personally, it seems simpler (and probably no more expensive when all is said and done) to use the ready-made battery system. They've probably optimized it and gotten the prices down via mass production in offshore plants... you will have to pay more for the parts, even if you work for free.

Just a thought...

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

air, glass, and mirrors conduct sunligt a whole lot better than silicon and copper. for light during the day some sort of window, skylight, or light-pipe will be much more efficient than a solar-powered LED.

I don't think you'll find a 5W panel on those cheepie garden lights: more like 0.05W

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Bye.
   Jasen

Thanks to everyone for the info. Sorry for the delay in replying. Bob has it about right. The ability to use the light in specific small areas is what I'm after. I agree the standard battery system would be cheaper but presumably it can't be charging and discharging at the same time, so it would tend to deliver light only later in the day.

I haven't actually used one of these battery systems, but I'd expect that there should be no problem with charge and discharge. In the morning, the battery will still be charged up from the prior afternoon. In principle you could have a *much* brighter light running from the battery, since it can charge over many hours at low current input from the solar panel, then put out a much bigger current for the short time you need it.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!