Scary IR laser sight for Idiot brother

[Lascannon]

Ok, so I have a reputation in my familly for knowing everything about lasers. I dont know everything about lasers. I know almost nothing. But I do understand most of the jargon, so when someone sais a 30mW 532nm handheld in a pressfit heatsink, I know what it means. So of course I must know everything. Slightly annoying.

Anyway, I am glad of one thing. He is consulting me, which means I can ask you guys how to complete his project safely. That said... We can dive right into it.

My brother has a rifle, with a infrared scope on it, and he wants to put a laser sight on it, one which can only be seen through the scope.

I am terrified of infrared lasers. Me. Not my brother though. This is the guy who came into my room, took the lock box out of my backpack, opened it, set aside the goggles so he could get to the clearly labeled 1W 445, and then blamed me when he nearly blinded himself. Before you blame it on age, he is 25.

You can understand my concern when he told me he wanted something we couldnt even see.

I told him "DO NOT GET ANYTHING OVER 20mW".

He said "Great, find me a laser."

So here I am. I need a relatively cheap, safe, laser. Clearly he will not be using goggles, but I will try to get him to buy some.

I have told him to find out what frequencys of light his laser detects, and I am hoping it will detect 808nm, since that is common (I think) and relatively cheap.

So yea. ANY advice is welcome, I am terrified that he will hurt himself or others. By, say, leaving it on. Looking into it to see the diode. Blinding himself. Dropping it on the ground. Shouting for help. Someone else walks into the room. Now they are blind as well. Now the carpet is smoking, and a fire has started. Now we have a blind familly in a burning household.

Ok, thats unlikely, but you get the idea.

HHHHEEELLLLPPPP!!!!!!!

Thanks!

 

[joeyss]

Just tell him to get a Narrow spred IR Led please.....this is an accident waiting to happen unless he uses a beam expander.

 

[jeffreythe00]

You can extract IR CD reader diodes from just about any old CD player, DVD player and so on. IIRC these diodes are singlemode diodes and are low powered. Now I'm not entirely sure what the divergence is going to be like... But you get the idea.

Basically this project is feasible and its possible for nobody to get hurt.

Now if you were looking into higher powered IR diodes. They start to go into multimode and you will end up with a IR flashlight rather than a laser.

Hopefully someone else will chime in and explain a bit more if needed.

 

[Lascannon]

Is it possible to get something under 20mW (I think that should be safe, right?) from an old security system or something?

 

[Cyparagon]

This is what you want. Low power, safe, cheap, single mode, visible on IR gear.

 

[JLSE]

Id recommend a diode from a PHR sled red/ir combo. The NIR can go to 20-30mW
and will run fine at 1~5mW. The divergence is similar to a red, and his scope
should be able to see it fine without the need to run something high power.

Like mentioned above, an IR diode from a cd burner will also work and has similar
divergence, but im not sure how stable they are when you drop the output.

The PHR diodes are reader only, so should be far better suited.. Also you have the
option to wire a second driver and switch to run the red at 10-15mW if so desired.


:beer:

 

[Lascannon]

Ok, all these links are great... but I'm not building it. I have washed my hands of the project, and am only helping him not kill himself. I can see how it would go already.
I build him a laser
He blinds himself with his laser
I get blamed for it because I built it.

Not going to happen.

But If all else fails I will explain to him how to build one of these. In that event:
What housing should I use?
What driver should I buy/build?
What power suply?

Thanks,
Liam.

PS: Anyone know where I can buy a complete laser?

 

[HaloBlu]

To really wash your hands of it just point him to a obscenely expensive pre-made IR sight.
Throw in some lies. Tell him all IR laser diodes with proper wavelength & divergence for a NV sight will be expensive.

Don't fall for any suggestion that not helping hurts your reputation or knowledge. Its the other way around. Your right to be cautious of infrared.

If you do want to show him what to use, I would go for a CD laser (780nm) like the PHR red/ir combo that wannaburn recommended. Direct hits in the eye will be more visible then 808nm but (I would expect) you shouldn't be able to see the dot at range without NV / camera.
Perhaps an 5mw 780nm module from aixiz or ebay? Some have drivers that take 3v. Add a couple of aaa & be done with it? You could use a li-ion with a LDO 3v regulator.

Oh yea, how about having him use duct tape as a heatsink in hopes that it might burn out in short order & you can blame his shoddy work. :evil:

 

[Lascannon]

Honestly, I just want to point him at a full laser module with a driver and a heatsink, all ready for power. I would rather not lie to him to much, if possible, but I do want to explain to him that this IS NOT SAFE!!!!!

 

[Cyparagon]

I linked one for you already. It's a <5mW module - there's no reason to be afraid.

 

[Lascannon]

Wait, but does it have a driver? Or does it not need one? sorry, like I said, I have only ever completed one build. Thanks!

 

[Things]

Yes, it does have a driver. Get a 2x AA or AAA battery holder, a switch and that module, mount it on the rifle, done. 5mW is going to take a bit of work blinding someone even if they stare directly into it for a few minutes.

You might want to add some teflon tape or a drop of glue to the lens thread once it's focused to infinity, or every time he fires it'll go out of focus again. Will also prevent anyone from getting their eye in the focal point.

 

[Lascannon]

Simple as that, eh? Thanks so much guys!
+Rep

 

[Bluefan]

I'd say stay below 1mW, the mentioned IR lasers are on the border of what is visible but they won't trigger a strong blink reflext. Especially if someone is known not to take laser safety serious I wouldn't give anymore than 1mW. Higher power could be used safely in the right hands.

 

[Lascannon]

Well, we had a nice little chat about it. I emailed him a parts list, a complete and detailed instruction set, and told him how powerful it was and how to treat it. I had an idea. He is VERY persnikity about gun safety, allways scolding me for holding it wrong or letting the barel drift even slightly up range while it is loaded. I told him that he should never take it off his gun. Now, even if he leaves it on, it will either be in a case, or pointed in a safe direction, or in the rack (enclosed, dark ended, locked) until it runs out of battery.

Thanks guys! This should be perfect.

PS: The route of the problem is that he doesnt take lasers seriously. As a hard-core competative shooter, he has trouble with the idea that anything electronic should be treated with the same care as his beloved SPP.

 

[HaloBlu]

Some safety issues require accepting things you might not understand, he seems stubborn on that point. I could be wrong but I think eyes are fairly important to competitive shooters. For his own benefit he really needs to accept dangers to his eyesight even if he doesn't quite get it.
He wears shooting glasses, no?
Just wondering, has he ever seen videos of lasers igniting objects?