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Registered Member #62109
Joined: Sun Jan 28 2018, 10:00PM
Location: Porto Alegre
Posts: 56
Hi. I have been observing some curious stuff in some trees here. The branches which take sun all day, "pop" a lot of new branches. So I was thinking about some shape of lens that would make the sun light hit always a same spot on the tree during almost all day. But then I remembered that concentrating light this way, I will just make the tree light up like a torch. I think I need a lens that gets light from various directions and make it come strait from the other side. But without focusing it too much. Just a little more intense than normal sun light.
Registered Member #62109
Joined: Sun Jan 28 2018, 10:00PM
Location: Porto Alegre
Posts: 56
That is what I need. Well the sun is too far, so I can't use the second option. But I have seen people using fresnel lenses to burn things or to cook food. Maybe if I turn the lens around? I'm not sure if if would work the same way on both sides since I don't have one here to test. Thanks for the help.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Andre... all you need is some clear plastic like 20 mil thick and a hoop and some kind of stand.
All you do is attach the plastic sheet to the hoop loosely and put it up on a stand. Then you fill the plastic with water and adjust for how much magnification you want, then use a large flat mirror to direct the light.
When you get bored with that, you can use the "lens" to burn stuff, just remember to wear shades or you'll go blind.
Registered Member #62109
Joined: Sun Jan 28 2018, 10:00PM
Location: Porto Alegre
Posts: 56
Hmmmm, I saw that in these survivor programs on TV. I will try to build one. Oh I did some burning already when I was a kid, but never wore the shades.
I will make a little one and then I come back here if it works. 5cm or 2 inches in diameter. Thank you.
Registered Member #62109
Joined: Sun Jan 28 2018, 10:00PM
Location: Porto Alegre
Posts: 56
Hi Conundrum, I just realised I can't find any of these around here to buy. I will try first with some cheap magnifying glass and also the water lens. If it works I may buy something on the internet.
Thanks Sulaiman, maybe I can put together something like that. I only need to measure some angles, or just get a mirror, go there and try.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I guess that building a heliostat is a major project in itself.
You could try a static mirror arranged to sweep the bright spot across the foliage as the day progresses. A large mirror should provide the equivalent of maybe 1 hour extra sunlight per day. If this is significant then a band of different growth should be seen where the spot travelled each day.
Or just hang a sheet of Al cooking foil behind a test leaf/twig/branch for double sunlight ?
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Maybe a CR servomotor or one beefed up using a larger motor, gearbox (hint: swipe one from an old school stereo with the motorized tuners) and the original trimpot. For this application high speed is not required. Also relevant, use a simple magnet and 4 pin linear Hall sensor from a defunct VCR or floppy drive motor assembly
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Lens to make sun light on a same spot
