Solar Death Ray (TV Fresnel Lens)

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Introduction: Solar Death Ray (TV Fresnel Lens)

About: Ordinary guy with no special skills, just trying to change the world one backyard invention at a time. See more at: http://300mpg.org/ On Twitter - @300MPGBen and at Ecoprojecteer.net

For all of you would-be eco-friendly mad-scientists, I present to you a way to dominate the world! But only on sunny days - THE SOLAR DEATH RAY!

This is simply a free projection lens from the front of an old television, mounted in a wood frame. It's any easy project anyone can build with only simple wood-working skills.

I got this lens from our local electronics recycling center. The public can drop off old televisions, computers, or other electronics for free recycling. I simply used my swiss-army knife to remove the few screws that hold on the bezel, and then slid the lens out. There must have been at least 5 junk projection TVs there when I did this.

The lens is roughly three feet by four feet, with a diagonal of just over 60 inches. 

To make the frame, I ran 2x4's through a table saw with the blade depth set to about half an inch. The plastic lens is about 1/8 of an inch, the same thickness as the width of the saw blade.

The 2x4's are then placed around the lens, with a pair of wood screws in each corner to hold the frame together. The wood was left long to act as handles, and make the Death Ray easier to hold and aim.

At this point, I haven't built a stand for the lens, but may in the future. As it is, the Death Ray works well being held by one or two people, and not having a stand discourages leaving the lens in the sun unattended.

This past weekend, we had a children's birthday party, and it was a sunny fall day, so we broke out the Death Ray and melted pennies. Some of my friends are science teachers, and children LOVE to see things like this. (So do the Adults!) Needless to say, there was plenty of adult supervision.

Modern American pennies are mostly Zinc, which has a melting point of about 800 degrees F. They are coated with copper, which has a melting point near 2000 F. We were able to liquify the pennies. An auto-darkening welding helmet worked well to allow me to look directly at the target object and adjust the focus.

The Solar Death Ray is loads of fun! I highly encourage you to make one. Just make sure not to leave it unattended, or where children could use it unsupervised, as it focuses a serious amount of solar energy. I keep this covered with heavy dark cloth if it is outdoors. I store it in my dark garage.

Be safe, and have fun with the SOLAR DEATH RAY!

The Solar Death Ray is now on the Web, Facebook, and YouTube! Come say hello, watch the Solar Death Ray destroy things, and make sure to subscribe!

Web: http://www.solardeathrayvs.com
Facebook: https://www.facebook.com/solardeathrayvs
YouTube: https://www.youtube.com/channel/UCrKlF-Iuh6M8d216dCJZgCA

For more of my recycled backyard fun, please visit http://ecoprojecteer.net

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38 Discussions

I was interested till I read about the pennies. Then I was impressed.

Just pulled one of these screens out of a dumpster yesterday. Now I know what to do with it. I plan to take it camping... " Who wants to bet I can't start a campfire in three seconds without matches?" LOL.

smaller versions in the old type of overhead projectors used in schools. Located just under the top glass. much more manageable and probably not so much "death ray".

If you want to BUY a large lens like this, they do sometimes show up at Surplus or Scientific stores. Here's a link to one of the types of places you can find them.
http://www.sciplus.com/

Another fresnel screen option is to find some the "old-school" overhead projector machines. Under the flat-glass top is a 14 X 14" fresnel screen with the infamous circular flexible screen pattern. It does about the same thing only not so big and not so flimsy. Much more manageable! And schools are disposing of these machines like crazy. I got 4 screens for free!

1 reply

see my reply above about finding smaller versions of the fresnel screen inside the old-type overhead projectors. Get a bunch for free I should think.

I wouldn't buy one. This is a project in recycling. The lens is part of a common older style television that gets thrown away now. You can find them at junk-yards, recycling centers, or by asking in classified ads.
If you really want to buy one, I sometimes see them in Scientific and Surplus stores.

We made one a couple of months ago...very cool. Got the tv from someone who was advertising it for free, was just going to throw it out. Definitely have to do!!!

Very fun Instructable! I will hit up our local recycling center for a lens and perhaps try blacksmithing with it. However, I see you have a wonderful white smoke coming from the pennies. Please don't sniff those fumes. Burning zinc and copper emits fumes that cause Metal Fume Fever. It is nothing you want to deal with. I lost a friend to it. The American Welding Society (AWS) has a nice little article about Metal Fume Fever at: http://www.aws.org/technical/facts/FACT-25.pdf. Other than that, you've got a wonderful project there! Thanks for posting.

Engineers in London did a similar thing. Mostly by accident.

http://www.gizmodo.co.uk/2013/09/its-not-just-cars-londons-walkie-scorchies-setting-fire-too/

I like the lab coat you must be a reel science person just like on the picture box at aunt Mabel's over head projectors use them also and you get a couple of glass lenses too
I hope the local ant colony's are paying tribute

Could this help make a solar oven function better?

Why?

PLEASE NOTE:
Not ALL projection TV screens use fresnel lens, so not all TV will work