If a small magnifying glass will burn things with sunlight, how much power could you get
from a lens as big as you? In this project we're hacking open a rear projection TV, because
that's where you can find one of these amazing solar scorchers, for free.
To get started, the first thing I'm gonna do is log online to my local classifieds
and search for a free big screen TV. These TV's are way outdated and usually cost more
to repair than they're worth so loads of people are trying to get rid of them. I can already
see one here. It's a 50" Toshiba and it looks like it's about 13 years old. Everything works
except the color and that's ok because I don't really intend to watch TV with it. These TV's
are humongous and very heavy, so I'm gonna need a truck and a little help. Now heres
my brother with his truck. He's gonna help me out today. It 's about lunch time, and
he's on his break. We've just arrived at this ladies house, and stepped inside to thank
her for donating her free TV. The price was certainly right and I'm a happy customer.
Now you gotta watch out these TV's can be a couple hundred pounds so I don't recommend
lifting them on your own. Luckily this TV has rollers so we'll roll it over to the truck
and load it with the screen facing up. We don't really care too much about the condition
that this travels in, as long as the screen is protected.
Now it's time to head back home and start hacking this TV apart.
I'll unload the TV from the back of the truck. It is VERY heavy and unfortunately my brother
is back at work, so I'm unloading it by myself. But it's down now, there's some success. The
TV is now in my back yard and I can get to work.
First thing I'm going to do is remove this speaker guard to expose the speakers, and
I can take these and remove them for a future project. These are 8 Ohm speakers and I'm
sure I can find a good use for them. Now just above the speakers I found a couple of tabs
holding the screen in place. After removing the 2 screws on each side, the screen lifts
straight up and pops off exposing the inside of the TV.
You can see at the bottom, the Red Green and Blue cathode ray tubes with their respective
lens casings, as well as a nice big mirror. Now since this mirror is used for projection,
it's super reflective so I'm going to remove the screws holding that in place, and save
it for a different project.
This TV screen has 3 separate layers. It's hard to see, but the front layer is a large
piece of plexiglass, that could be useful. The middle layer is a vertical lined plastic.
And this back piece is a giant virgin Fresnel lens. This is the piece that I'm after.
I got lucky because this one happens to be a crystal clear lens that focuses to a point.
And that's the best that I know of.
It may not look like much but this is a giant 4 foot magnifying lens! The amount of energy
these lenses can generate is outstanding! Producing temperatures over 2000 degrees fahrenheit.
They can be used for heating, cooking, purifying water, and burning almost anything
you can imagine.
Amazingly, they do all that just off sunlight.
Now that I got the lens I was after, I'm going to play
around with some of these other pieces on theTV.
These projection lenses, the caster wheels and the power cord can all be saved, and just
for fun I'm going to take one of these lens cases and hack it open to see what's inside.
I'm gonna save these nuts and bolts and then cut down the side of the casing here.
And when it's cracked open, you can see about 5 different optical lenses. Now these are
really neat because they're in perfect condition, and I may be able to use them in future light
experiments. Most of the them are plastic, but this focusing lens right here is pure
glass. It's quite heavy, and the optics on it are amazing. If I focus it on my table
as if I'm trying to burn the table, you can see it brings into focus the Compact Fluorescent
Lights that I'm using to light the room. I thought that was kind of interesting.
Ok, I've got the giant Fresnel lens, separated from the frame now. You can see it's quite
flimsy and awkward so to hold it I think I'm going to need to build some kind of a frame
so I can use it hands free. Look for that in a different project.
Well there you have it. Now you know the secret to finding a giant Fresnel lens absolutely
free!
Now, a word of caution, these lenses generate a lot of power. They can concentrate the sun
to a point that gets dangerously hot. It will start fires instantly, melt concrete, and
can certainly cook you, so be please careful.
That's it for now. If you liked this project, perhaps you'll like some of my others. Check
them out at www.thekingofrandom.com