Sun + Magnifying Glass = ?mw

[caleb]

i think im gonna buy that if shipping not to much on my money
and here you go the same one
[highlight]13inch fresnel lens[/highlight] http://www.youtube.com/watch?v=SGNcFV4no5Q

 

[Benm]

13" is about the size used in overhead projectors (it fits an A4 transperancy in portrait and landscape usually). Plenty to light the fire on a sunny day.

 

[artix]

i think im gonna buy that if shipping not to much on my money
and here you go the same one
[highlight]13inch fresnel lens[/highlight] http://www.youtube.com/watch?v=SGNcFV4no5Q

Yeah that is where I first saw a Fresnel lens...

 

[tatman]

Don't buy a fresnel lens. Keep your eyes open and the next time you see a big screen TV that is on it's way to the dumps...score! I got mine that way and I bet it is at least 3' x 4'.(Thats three feet by four feet.) If I ever figure out how to post pics/vids you will be blown away! This sucker will Light a 2x4 in under a second!Thats like instantly...I was stunned as it was afire while I thought I was focusing it. And to just plain aggravate somebody I suggest one of those mirror tiles. On a sunny day you could easily drive a distant target nuts.

 

[Switch]

Damn, that fresnel should be focusing more than 1kW You have to be careful with that, it's downright dangerous, to eyes and everything.

you have a 4 watt.where is it from

It's on the project list.Don't know if I'm gonna be able to raise the funds for the 4W diode, I think I'll settle for the 2W.It's still more lasery burning power than I've witnessed so far :-/

 

[tatman]

Super dangerous. At first I gave it no thought. But I changed my mind when I saw how fast it can light stuff. And we're not talking about some little whif of smoke - I'm talkin full, hot robust flame in less than a second. Crap , Ican't light a 2x4 in less than a second even with matches/lighter. Crazy.

 

[Dark_Horse]

Super dangerous. At first I gave it no thought. But I changed my mind when I saw how fast it can light stuff. And we're not talking about some little whif of smoke - I'm talkin full, hot robust flame in less than a second. Crap , Ican't light a 2x4 in less than a second even with matches/lighter. Crazy.

Sounds like we need a GB for "big-screens"
DH

 

[laserguys]

My magnifying glass is about 5cm in diameter, and on a hot summer day it can easily set old leaves, newspapers etc. on fire. I would estimate it to be equivalent to about a watt of laser light, but I'm not sure. A 10cm circle should be a lot more than a watt.

If the suns power really is 1kw/square meter, it would be pretty easy to do the maths. Then, the power per square decimeter should be ten watts, and a 5cm square would be 2500mw. if you take a 5cm squares power multiplied with 3.14 (pi), you would get the power of a 10cm circle. 2500 multiplied with 3,14 is 7850. With a 10cm magnifying glass you would then obviously have 7850mw of sunlight to work with. But that is of course IF that statement about the suns power/ square meter is correct. Wouldn't that value depend on which time of the day it is, which time of the year it is, etc? How can that be a constant number? :-?

Well while you guys are calculating the suns potential power.............
I went outside at 3:45 PM EST near Montreal on a cloudless day with
a 1-3/4" diameter glass magnifying glass and placed a 1/8" diameter
focused sun beam on my LPM and got a reading of about 890mW.
(I shake a little ;D)
Without the magnifiying glass (straight unfocussed sunlight) I got around
37mW.

So go out and see what you guys get.

 

[caleb]

well atleast someone finaly did it...

 

[artix]

[quote author=tatman link=1218964146/20#21 date=1219259709]Super dangerous. At first I gave it no thought. But I changed my mind when I saw how fast it can light stuff. And we're not talking about some little whif of smoke - I'm talkin full, hot robust flame in less than a second. Crap , Ican't light a 2x4 in less than a second even with matches/lighter. Crazy.

Sounds like we need a GB for "big-screens"
DH[/quote]

Then I, am in!

 

[Murudai]

Kinda depressing isn't it

We get these massive, expensive lasers. And a clear piece of glass can burn better

Ah well, I don't really buy lasers for burning anyway. My only designated 'burner' is my 290mW red MXDL. My next burning 'laser' will be a fresnel lens ;D

 

[TheMonk]

I bought a set of 4 magnifying glasses for $3, very good quality.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96030

 

[jamilm9]

i have a 11 by 8 inch lens

 

[JLSE]

Okay, I figured I jump in and try a few things. I too am guilty of burning bugs as a kid, and havent tried this in years. I have in my possesion a cheap fresnal and a monster lens from a drive in movie projector Both produce (as expected) a super hot spot. So I figured I try putting a greenie crystal set in front. I tried different positions, angles etc. and at most can only get a bright violet spot similar to that of putting a flaslight behind it :-/ The only green produced was the reflection of the KTP's AR coating. It was a fun idea at the time but now I will be seeing spots for a while

 

[pullbangdead]

Kinda depressing isn't it

We get these massive, expensive lasers. And a clear piece of glass can burn better

Yeah, but it's REALLY hard to see the beam at night

 

[jamilm9]

hehe.