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Well, this is highly irregular.

Volfram

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I usually try not to create new threads. And here I'm making one as my first post. You people really need a "Newbies, introduce yourselves here" thread.

Several years ago, when pen-style laser pointers became cheaply available to the general public, my dad said that he'd buy one when he could "burn a hole in the projector screen from the back of the room." Well, his birthday is coming up in a couple of months, and from the looks of things, one could build such a laser pointer for under $200 at this point. You can probably see where I'm going with this.


I'm a Computer Engineering student from the state of Colorado, currently working a software debugging internship at a small company whose products are used extensively by the DOD. I'm interested in all sorts of dangerous hobbies, including firearms and knives, I own a Jacob's Ladder made from a broken down Ionic Breeze air filter, and when I was working on it, I managed to make my arm go all tingly by not noting which side of the switch was the switch and which side was electrodes. I've got a head for numbers, a taste for gadgets, and a personality which is best described as "crazy, not stupid," and I've still managed to somehow avoid seriously injuring myself.

And this seems like a good place to learn about laser experimentation and safety. "Always steal from the best," as my dad says.
 

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interesting, but i do have to say that , even the 8x bluray , is REFLECTED from a projector screen.

i get the whole idea of what you mean. i think that the bluray , 405nm, light will do what you want. look at the buy sell trade area and you will find things you want. i recommend DarkArmyofOne to build what you need and i recommend LarryDFW to give you a lens to collimate it all into a nice beam.

Arenared
 

Volfram

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interesting, but i do have to say that , even the 8x bluray , is REFLECTED from a projector screen.
I had considered that, and if I do give my dad a laser for his birthday, I'll be sure to include safety gear and documentation, after looking at some of the warnings that are repeated fairly often on this site, especially in the Safety and Legal area.
 

bobhaha

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Hey welcome to the forum! you are going to fit in well!! do you know what type of laser you are after at all?? like red, blue or green? as arenared said your best bet is with a blu-ray, just cause of its burning POWER!! check out jayrobs kits for the blu-ray builds! and i also reccomend a first timer.. to go with darkarmyofone for the build, since this is a pretty expensive laser you wanna get it right the first time!!

Anyway have fun, welcome and be safe! -Adrian
 

Volfram

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I was thinking a red or green 5-40 mw targetting beam so the user knows what it's pointed at and a 200+ mw Blue-Ray high-power burning beam that can't be activated without first activating the targetting beam.

That, or just buying one of jayrob's keychain builds. I actually found this site by following the breadcrumbs from Hackaday.com's article on jayrob's blue-ray keychain laser.

Given that I've got a couple of months to spare on research and money, and that Lasersbee has such a reputation, I'm thinking $20-40 is probably a good investment to avoid screwing up my first one.
 

hakzaw1

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Welcome Volf-- I think we already have a welcome(intro uself) forum. I am sure we can help you out. but remember to use the search before you ask. I think we would like to see photo/video of your J. ladder build, maybe even a tutorial on how to make one. I am sure its out there as a DIY but if you put it on the forum we could quizz you! :) I am new myself but i think you will have to make a flat black spot on anything you want to burn without getting up onto the higher mWs BRs.-good luck and have fun!!<(*u*)>--hak PS as for that irregularity- try fiber-works for me!!
 
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Volfram

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I think we would like to see photo/video of your J. ladder build, maybe even a tutorial on how to make one.
As it turns out, Ionic Breeze units work very similarly to the baseic Tesla coil/Jacob's Ladder model. When mine started to go bad and arc across the electrodes instead of simply producing air movement, I clipped the wires and replaced the electrodes with lengths of Florist's wire. When held parallel(not with hands, obviously. I don't know what kind of current is running between the wires, but whatever it is, it's high enough to arc, so I'm not going to risk becoming a channel for that arc.), the wires produce a rising arc between them, but because Ionic Breeze transformers aren't designed for high output like, say, microwave or neon sign transformers, the maximum spark length is about 3/4 of an inch.

Come to think of it, there's a $5 broken microwave at a local pawn shop. I should tear that apart and see if the transformer/magnetron are still live.

Anyway, so from the looks of things, a build for a Jacob's Ladder is basically the same as a build for a Tesla coil, except you short the primary coil and attach parallel electrodes to both sides of the spark gap.

I tried using the spark from my Jacob's Ladder as an ignition source for my flamethrower, but no dice. I don't think the spark gets hot enough, though it will punch holes in pieces of paper held between the wires.

Probably needs a bigger transformer.

(In case you can't tell, I have a very serious case of ADD.)
 

ZRTMWA

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My brother just left for Virginia Tech on Thursday to take general engineering his freshman year and then major in Computer Engineering the last three. A projector screen might be difficult to burn becuase it is usually light colored and especially difficult at longer distances. A targetting beam is a new idea (at least for someone who has only been on LPF for a month, yours truly) but it might be some what difficult to pull off. I would use a green for the targetting beam, as you will actually be able to see the beam, although 40mW might not be enough (except in the dark or with smoke/fog).

Your best bet is probably a kit from jayrob with an 8x blu ray diode and one of jayrob's blu ray lenses. Daguin and a couple of other members managed to get just over 500mW out of their 8x's with jayrob lenses. The kits, the diode, the lens, the driver, the batteries and the charger would set you back significantly more than $200 though but the other laser with the targetting beam probably would too. Hope I helped.
 

Volfram

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Not terribly concerned about the projector screen, the typical targets of such a thing would be flash paper and matches, which provide a really nice reaction. I was thinking a green targeting beam would be the best idea, because even if the beam itself isn't visible, the dot is a lot easier to see than a red laser. Importantly, I don't want the target beam to be a safety hazard. It's supposed to prevent accidents(such as shooting the burning beam at things you don't want burned), not cause them.

Besides, even mirrors typically have a reflectance of about 60%. I suspect projector screens would be significantly less, so it should still be absorbing around half of the incoming energy.(the other half is why we need eye protection :D)
 

cust11

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Welcome to the forum! I think you(and your father) would be more than happy with a sweet 405nm build! I also fully endorse jayrob's kits.

-Mike
 

ZRTMWA

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The green would need to be 5mW or less if you are concerned about safety although that in an eye can still cause damage.
 

sightfx

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you may want to scrap the idea of a targeting laser. 405mw is plenty visible. Especially at 400mw+.

If you are using the targeting laser so you can see where the burning laser will be with goggles on, I get it but alignment will be an issue. Unless the 2 beams are mixed (traveling along the same geometric line in space) you will either have the burner slightly off target or there will be a set distance where the beams cross and that distance being the only distance where the targeting laser is accurate.

If you do decide to go ahead with a targeting laser I would suggest you mix the beams by sending both through a Polarized Beam Splitter (PBS) cube. You will get some loss from the optics but the targeting laser will be on the same plane as the burner.

Another targeted burner approach would be to use 2 targeting lasers that cross at the set focal point of your burner. You will then know that where the two target dots come together is where the burner is focused to a fine, highly effective intense dot. You could use red and green target lasers so you know you’re at the best distance when the targeting dots become one yellow dot.

-SightFX
 
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