Using sky lights at night...

[ja2tn]

I have two solar tube type skylights I am going to put into my house/cabin.  This type of sky light, for those that may not be familiar, is the highly polished - highly reflective tube with a light gathering dome on top [on the exterior roof] and a diffuser on the bottom [on the interior ceiling].  The company these came from offers an incandescent bulb holder kit that mounts a bulb in the tube so you can use them at night also.  I am wanting to put in a series of LEDs and run them from a RE power source.  I would love to hear anyone's thoughts on this.  Have you done this or seen it done?  Things to look out for?  Why it won't work?  What will make it work?  ANYTHING?

Thank you so very much for the knowledge shared here guys [and ladies],

Jerry

in the Tennessee mountains

[ja2tn]

If you have posted on the previous post, please repost as the other discussion has disappeared.  You may also reach me directly at ja2tn@preferred.com but please post it here too so everyone can benefit from your post - never know when someone else has the same question but hesitates to ask.

[dudevato]

Jerry, I have a setup simaliar to what you want to do.  I have a regular skylight (2'x4') in my master bath that I put a solar nightlight setup into.  I used 2 of those little 'stick in the grass/path lights'  I took them apart and leangthened the wires between the 'cell' and the 'battery pack' (2 AA batteries) and then again between the batteries and the LED/circuit board.  I mounted the 'cells' on 2 small pieces of sheetmetal attached to the skylight's flashing and aimed them at the noon sun.  So the LED's are now about 3' from the 'cell'  They work great and put out enough light to do anything short of reading the paper.  They get a bit dim at 3am.  Every time I see these things in people's yards I think they put them in the grass so they look 'nice & neat'  I put mine exactly where they'd get the most sun.  Good luck with the project.  Post again when it's up and running.

[georgeodjungle]

we have two home brew solar tubes with garden lights in them.

works o.k. for night nights but not much more.

does light the dark parts with no heat gain or loss.

i did have a problem a wile back with one of the batteries, other than that every thing is good.

i should tie them in to the main dc power,,, one of these days.

i thought of the new "brighter" leds but i bought a 3 led flash light and it dosen't realy have the distance.it would be a lil brighter.

i mean up close it seems realy realy bright but like 10' a way it peters out.

i've seen the sola tube with the 60 watt light and thought about how hot it must get in side and why don't they use a fluorescent or led. cost? maybe but it's $300 for some pipe, plastic and a lil glass.

i don't have much luck with the compacts, but the leds rock, lil spendy.

i think the only other thing is wile the lights are on it shines or lights up the roof a lil bit. i can tell what lights are on and where. i like it, the miss doesn't.

it works for us.

[ghurd]

Again,

It will work.

For more than just a night light, go with a 12V CFL.

The 'diffuser' at the bottom of the light tube is going to cut down the light. A LOT. Probably better to have the LEDs exposed inside the room, than inside the tube.

Go with a higher voltage, like 4 batteries instead of 2 (and if you plan on using solar garden light PVs, use 3 PV in series instead of 2, and probably want to parallel 2 strings of PVs).

With those cheap LEDs, it may be cost effective and more efficient to double the number of LEDs and run them at 10ma. More light for the same power. Or even tripple the number and run them at 6ma.  Most LEDs are more efficient at 1/2ma to about 4ma.

Use wide angle (50~90') LEDs, or the light output will be either like a flash light or a disco ball.

With the garden light PVs what will make it work better is double the battery V, tripple the solar V, and (my opinion) try to use the mono or multi crystalline PVs. King size zener for a shunt charge controller.

My last toy like this uses a 12V VW PV like on ebay ($20), and 2 in series, 7.2V, 650mah, NiMh cell phone battery packs (2 for $1 surplus).  Works great, but the PV is surely overkill in the amps department, and I expect it to cook the batteries if they get too low.

LEDs are great for a small amount of light, but do not expect them to light up a room.  With white LEDs, in a properly designed 'bulb', somewhere around 30 LEDs and a small CFL will win on more light output for the power used.

G-

[Oso]

I have two solar tubes in my kitchen, and one in a bathroom. In the kitchen we installed the manufactures lighting kits. The two provide all the area lighting we need. We do have task lights over the sink and stove.

The good thing about the manufactures kit is that the bulb is suspended mid-tube on a thin steel support, most of the kit is outside of the tube. It blocks very little (unnoticable) light during the day.  On a clear night, starlight is visable coming through the tubes. When the moon is up, the is enough light to safely enter or walk through the room without turning on any lights.

My recommendation would be to use the mfg. kit, if the lights are going to be in the tube. Otherwise, just install whatever type of light you want elsewhere. Do not restrict your daylight for nightlights.

[ghurd]

Most (all?) of the ones I have seen have a lower cover that is very milky and will greatly reduce the light coming through from LEDs.  A clear prismatic lens would be better, but I have not seen one on light tubes.

About 21, 5mm LEDs can be fit in a standard light bulb base with enough patience, so it should not restrict the daylight any more than the empty socket would.

[ja2tn]

I am planning on mounting the LED's on a thin ring suspended in the center much like the manufacturers kit.  I will locate the LED's so that they shine 180 degrees [none facing up].  This shouldn't obstruct the normal light on the skylight much at all, especially with how efficiently this things use the available light.  The reflective tube should receive the light from all the LED's.  I don't know how many LED's yet, that is something I will just have to keep trying till I get it the way I want it.

[ja2tn]

I have three different diffuser options frosted [milky white], clear and then crystal [got the little diamond cuts on the inside like automobile taillight lenses used to be - only this is clear too]

[ghurd]

For the LEDs, go with the crystal.

Milky cuts LEDs down unbelievably,

possibly because of the narrow spectrum produced.

(I do LED stuff for a living, and will not bother with anything milky)

I'm harping on it so the finished design is at least useable.

Maybe crystal would be 'obnoxious' with full sun?