Burning stuff with a giant fresnel lens + how a DLP projector works

hey guys backyard scientist here you know I've always wanted to make one of those giant burning magnifying glasses that people make by taking apart old rear projection TVs I know it's been done a million times before but I just wanted to try it for myself anyway this is a lens that I got from taking apart an old television and you can tell it's a little bit too flimsy to use by itself so what I did is I sandwiched in between two pieces of glass luned it all together and now I'm waiting for it to dry overnight but while it's drying I want to show you how the projector works because it's actually pretty cool so if you look at this image right here it looks like a completely normal image but if you slow it down it begins to flicker and that's because it isn't one single image but rather a composite of five images and each image corresponding to a color on the color wheel so how this projector works is you have the light that is shining through the color wheel which has five separate colors on it and now light gets focused down onto this DLP chip this trip actually has over a million mirrors on it that couldn't even reflect the light towards this screen or bounce the light away from the screen so anyway when you're watching a video or something on the projector it's actually processing each frame then dividing it into five separate frames one frame for each color and then what it does is a placement back really fast and it appears like a normal image in fact we can actually measure how fast the motor is spinning so we can measure the output of the sensor that monitors the motors speed and see it's spinning it almost 240 times per second because it's flashing so fast we perceive it as a steady white light however if you move your eyes around really fast or wave your hand in front of the screen you'll see a rainbow effect appear on the screen well all right now it is time to burn some stuff but how much burning can we expect from this giant lens well they say in Florida that there's about an average of 1000 watts of sunlight that hit the ground every square meter and if this giant lens is about 0.8 meters I means we expect to get about 800 watts of light focus through this thing but due to some other stuff like the angle of the Sun in the sky the reflection of some of the light off of the glass and the glass absorbing some of the UV and IR light we can really only expect to get about 600 watts of power focused through that Lance now I say only 600 watts but 600 watts of power focused on to a penny is enough to melt it first I want to try overclocking a solar panel so the solar panel is rated at 5 watts what happens if we focus 600 wot's onto it will it put out a lot more power or will it just simply go up in smoke all right so if we measure the power output of this solar panel by itself so we're getting about 400 milliamps of current four tenths of an amp so now let's see what happens when we turbo charge oh wow look at that yeah so most I'm getting let's see about maximum 1.1 amps and that's on the whole thing but now what if we concentrate all of the power onto one little section of the solar panel let's try it dunt dunt dunt dunt okay it's actually dropping point one seven point one six [Music] point one go yeah I'm not breathing actually this has been exhaling this the whole time Wow a little warning occur so now let's let's try the whole thing again and see what we get what are you getting point four so you broke it so it looks like I just by messing up one cell because these are all wired in series oh yeah I must have permanently messed up this solar panel so depending on the orientation of the Brinell lens if it's based one way or the other you'll either get this really nice sharp focal point or we'll flip it around and show you it's not as sharp as a focal point you can see that it's actually more of like a parabola shaped focal point all right Riley armed the laser I gotta say that shaving cream cans are my new favorite thing to destroy they're pretty loud but it happened so fast even on high speed great success all right a lot of people were curious what would happen to sunglasses so we've got some black sunglasses and clear sunglasses because I think this light might be so intense it could even burn the clear ones but first let's try the black sunglasses all right here we go okay it's right here Wow you know they're actually less better than I thought oh there they are now it's on fire the black sunglasses did not fare very well they're covered in holes totally melted now let's try the clear sunglasses leave it on there for a couple of seconds see if anything happens it's like hot it's burning me through the glasses it doesn't look like it's heating up the glasses now we're gonna be trying to melt some lend pellets for my BB gun let's see if we can film admittedly LED is pretty easy to melt as a very low melting point oh wow come come see it blood was pretty easy now let's try to melt some pewter so you've got this pewter mug we just got a goodwill whoa it melted a hole right through it didn't it well it's hot did you did you get that whoa you see that yeah I don't be wearing a gas mask it's just pewter what about what it was a lid it's not gonna let hot enough to vaporize anything with smoke that's from like the wax on the lid to keep it from like rusting okay if I don't have heavy metal if I don't have heavy muslin maybe I do have heavy metal poisoning if I don't have heavy metal poisoning by now you will be fine all right well it looks like we completely melted that pewter picture look at that it did take a while probably about five or ten minutes but oh no we did completely melt that pewter picture and turned it into a beautiful shiny pool of molten tin look at that the power of the Sun here's just some popcorn we'll see if we can get it started and then you know we'll do the actual rest of the popcorn in a bowl or something so here we go but this might be better because we won't focus it but instead we'll leave it kind of wider so we don't just burn the popcorn I think I see something happening Oh popcorn go Oh popcorn huh that's pretty funny now we're going to see what happens if we do eggs so first we're gonna try a brown egg and then we'll try a white egg so I'll just put like the egg right here all right and screwed it in then what happens we'll just have to wait and see well that is pretty hot what do you say that's been like a minute yeah you know take it out and see what it looks like basically a glowing orb on camera it's no cold is it yeah you can hold in your hand oh yeah look at that [Music] oh yeah that's smoking really good oh it smells so bad did you see that yeah oh it's popping out come get a close-up of that well I can't say I actually expected the egg to get cooked but that was just nasty anyway sander heard us having all the fun and decided to come out and try it for herself I leave you alone for one second all right so let me show you you never really showed you how here it goes that wood on fire it was like that two seconds it touches the one hand and boom it goes on fire and you know I saw it grant Thompson you know so let's try that does it look great on to you where's it just the glasses oh wait I set the wood on fire oh there you go Oh alright guys that's the end of this video I hope you enjoyed it got another one a good video coming up soon involving the new for night update take a guess what that is not a good idea so so we'll try that and we'll post a video see you guys soon fine

Channel: TheBackyardScientist

Views: 1,049,023

Rating: 4.9314051 out of 5

Keywords: fresnel lens, fresnel, how DLP works, dlp projector, the backyard Scientist, thebackyardscientist

Id: J_evWNVWIYc

Length: 8min 32sec (512 seconds)

Published: Thu Apr 04 2019

Reddit Comments

[u/the_nybbler]

The smoke might contain solid particles of lead or lead compounds, which probably isn't healthy for you either.

[u/snet0]

Lead's boiling point is 2000K, and lead oxide is pretty close behind. The smoke is just like he said: impurities, coatings etc.