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Fresnel lens

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Fresnel lens

Postby arkieready » Mon Jan 16, 2017 8:10 pm

Ok, I searched this place for threads on fresnel lens. I found exactly "0" results!!
Did they disappear or has no ever brought them up?

I have a few small ones. Green science power.com has videos and supplies for projects.
What have you done with them?
P!

Happiness makes up in height for what it lacks in length.

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Re: Fresnel lens

Postby DR1VENbyKNOWLEDGE » Mon Jan 16, 2017 10:17 pm

Hmmm....surprised there's no threads...interesting as cookers as I've seen them used that way and also melting softer metals.

This guy gets really excited for a good lens...lol https://www.youtube.com/watch?v=xExXjXm0YV0

hoping to see some practical replies here...popcorn in hand. :)
In honor of RebNavy...RIP buddy. You made me smile. :)

Postby rebnavy1862 » Fri Apr 07, 2017 4:00 pm
Driven, are you sure you are from Kalifornia? You make a lot of sense.
Reb"Then call us Rebels if you will, we glory in the name, for bending under unjust laws and swearing faith to an unjust cause, we count as greater shame". Richmond Daily Dispatch May 12 1862
Semper Fi, Sic Semper Tyrannis, Remember The Alamo, and Aide'toi et Dieu T'aidera!
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Re: Fresnel lens

Postby daaswampman » Mon Jan 16, 2017 11:47 pm

Try this site. They are greenies, but have info, good prices, and good service. I prefer parabolic mirrors to fresnel lenses, but have both. On a sunny day I can boil a cup of water or solder with a mirror the size of my hand that weighs an ounce. Be careful as the big ones can cook a toe in a blink of an eye! I was lucky and only lit a shoe on fire! Swamp

http://greenpowerscience.com/index.html
People rarely notice what it right in front of their eyes. The Da Vinci Code
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Re: Fresnel lens

Postby arkieready » Tue Jan 17, 2017 8:03 am

Thank you, swamp, for posting the correct link. I mangled it.

That guy, Dan Rojas, has a nice site. Parabolics, too. And projects for water lens. Food for thought.

I have boiled water in a beer bottle with my cheap little lens. And burned stuff, of course.
But my idea was to combine a sun oven with a fresnel lens to cook quicker and hotter. Not done that yet.
I know distillation for clean water is doable. What about solar water heater plus fresnel lens boost? I'm thinking using a lens to boost any passive solar project would work. Including those passive solar "window heater box" thingies. Even off focus cheapies produce a lot of heat. My 5x7 $5 one was dangerous enough.
I still think there HAD to be threads or subjects here. Maybe they got lost in the move.
P!

Happiness makes up in height for what it lacks in length.

--Robert Frost--
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Re: Fresnel lens

Postby Argus » Tue Jan 17, 2017 12:55 pm

I have salvaged a couple of them from old projection TVs seen by the curb on trash day. TV repair places might have non-working ones, or you can find them on Craigslist. On a sunny day you can melt a penny with them, or boil water in a can as stated above, or start a fire in seconds. They can break easily. With a frame built of 1x2s slotted lengthwise by running them through a table saw or with a circular saw you can make a holder for it, but you'll need to move it as the sun moves to keep it focused. Also, don't look at the concentrated light with no protection, it will give you a heck of a headache and probably damage your eyes. I used doubled welding hood lenses and it seemed to work well. These lenses are capable of instantly charring skin or setting fires if left unattended, so use caution, the larger they are the more powerful.
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Re: Fresnel lens

Postby arkieready » Wed Jan 18, 2017 8:05 pm

I wondered if there were YouTube videos of a lens direct heating a Dutch oven. Yes! Combining lens and a homemade sun oven. Yup. Lens and reflectors. Indeed.
P!

Happiness makes up in height for what it lacks in length.

--Robert Frost--
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