Solar Garden Lights

[The Medway Handyman]

Just been looking at this site

the FAQ section is the following;

Q) I tried to charge my new light under a lamp and it does not work. What should I do?

A) Our lights will not charge indoors under a lamp with artificial lighting. They need to be placed outside in direct sunlight to charge. Before packaging lights the batteries are tested and 30% charged. We recommend placing allowing up to full 3 days of sunlight to fully charge the batteries before initially using the light.

How does that work then? I thought light was light?

[Bob Minchin]

"Light" consists of a broad spectrum of frequencies some visible to the human eye, some not. Artificial light tends to be narrower band than sunlight and also photo voltaic cell in the garden lights will have their own variation of power out for different frequencies.

An unrelated and useful bi product of this type of differing frequency sensitivities in electronic devices is the ability of most digital cameras being able to respond to the Infra red frequencies from remote controls. If you suspect your tv remote is not working, just view it through your digital camera which effectively converts IR into visible light.

Ain't science wonderful!

Bob

[Clive George]

Sunlight is rather brighter than most artificial - a camera will confirm this for you :-)

[Harry Bloomfield]

The Medway Handyman explained on 02/05/2009 :

Shine even a 500w flood on a wall in broad daylight and you would have some difficulty in telling if the lamp was on or not - all due to how dim lamps are when compared to sunlight. Hence the photocells need the sunlight hitting them to produce any useful output.

[John Stumbles]

Incidentally I stuck some full capacity NiMH cells into some cheap solar lights I bought, replacing the part-capacity ones that were so lightweight they must have been practically empty, and they run practically forever once they're charged up.

[Al]

You were mistaken.

Sunlight is really, really, *very* bright. 1.3KWH per square metre or there abouts. Creates more global warming than, well, anything else really ;-)

Artificial lights produce an, erm, 'artificial' light. Very low colour temperature, zero energy up towards (and beyond) the violet end of the spectrum.

You can buy pro light meters (I have one cos I worked on interior lighting systems many eons ago), or buy a ten quid market-stall solar battery charger and measure the voltage/current.

Sunlight is very, very strong :)

Al.

[TMH]

However they won't charge in a single day so they last about the same time each night as the cheap ones fitted.

[A.Clews]

Thus spake Al ( [e-mail]) unto the assembled multitudes:

Indeed - consider one of those 500W security lights your neighbours use to light up everyone else's property. That 500W lamp shining on a square metre of surface will yield a fraction of the energy from sunlight, and a lot of that 500W is dissipated as heat anyway.

[The Medway Handyman]

Oh goody. I had some of those 'rock lights' with 600mAh AA's in & replaced the dead cells with 1300mAh. So as long as they get a good charge, I'm ahead of the game.

[The Medway Handyman]

SWMBO came home today with a solar LED light from DSL, purchased from Morrisons.

The destructions say; "You can also charge the solar lights outdoors then use them as indoor illumination"

So that confirms that sunlight is stronger or of different wavelength than internal lights.

Well I'll go to the foot of our stairs.

[Clot]

I was helping to run the local May Day carnival in town today, a heavily overcast cold day, when I bumped into a friend who said "The UV is strong today".

Being an Old Fart with little up top, I thought he was referring to the sun, that I had not seen, affecting my complexion. Nope, my photochromic lens were black.

[Clot]

[Clot]

Ooops, sorry I was distracted when I originally sent this!

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Clot" saying something like:

Lenses too dark?

[PCPaul]

Both.

It's far stronger - I have a nominal 250W 'daylight spectrum' bulb and the sun through the window still casts shadows when it's on.

The sun is also much wider spectrum than any bulb - around 300-2500nm wavelength at ground level. We can only see 400-700nm(ish). Even top quality 'daylight spectrum' bulbs don't bother trying to match the further reaches of Ultraviolet or Infrared - and we can be glad they don't...

[The Medway Handyman]

Yerbut, nobut, yerbut. At the front of handyman towers I have a dawn dusk lantern (no PIR) with an 11w thingy bulb (sorry, lamp) and about 8' away on the front of the garage I have a 500w halogen light (manually switched, no PIR).

If I'm loading the van at night & switch on the 500w jobby, the dawn dusk goes out, until the 500w is switched off again. So (a) how come the 11w lantern doesn't switch itself off evey time it switches on and (b) its seems to react to a 500w halogen just like sunlight.

My brain hurts...

[Dave Osborne]

The sensor in the dusk-dawn lantern is located so it is in the shadow of the lamp, so the lamp does not trigger the sensor.

Clearly, when you switch the 500W halogen on, the beam from the halogen

*does* impact on the dusk-dawn sensor.

This indicates that the dusk-dawn sensor is quite sensitive (you may notice that the lamp doesn't come on until it's pretty dark and goes off at the first hint of dawn). This is good for environmental reasons!

If there is a sensitivity control for the dusk-dawn sensor then if you turn the sensitivity down (i.e. towards the sun icon) then the halogen won't trigger the dusk-dawn sensor and the dusk-dawn lamp won't go out when the halogen comes on.

[John]

A camera that shows the shutter speed / F number will confirm the relative brightness. (or lack of brightness indoors).

[PCPaul]

The sensor on the 11w dawn/dusk will be a very primitive (i.e. cheap) photocell used to trigger a solid state switch. All it measures is brightness - it doesn't care what it is, unlike solar cells. The normal (cheap) Cadmium Sulphide photocell is sensitive to the whole visible range and a bit further, into the infra red.

Your 500W halogen light will be kicking out a LOT of infrared (or, as many people know it, heat).

The reason it doesn't switch itself off is (usually) simply because the sensor is let back a bit into the case - light travels in straight lines so its own light doesn't reach its own sensor.