Laser Gun Project

[fechter]

Well, johnrobholmes was right. The repeated short spike I was getting with my driver circuit finally cooked the diode. It still lights up and makes a beam, but very weak. $50 educational expense.

I replaced the driver with an "X-drive" sold by the guy that has the diodes. I also upgraded to a more powerful Nichia NDB7875 and got a G2 lens to test. I liked the two stage trigger, so built an analog driver from a LM317 for the low power mode. This seems to work great and there are no more spikes in the output. Low power mode is 150mA and measured 42mW output. This is great for aiming/focusing.

I measured the NDB7875 output with the G2 lens on my fancy power meter at work. It starts out at 3.2W and warms up to right around 3.0W. This is enough to make wood burst into flames at close range. The Axiz lens measured around 2.5W but makes a tighter beam at long distance. It definitely pops ballons from across the room now.

 

[Nehmo]

... laser weapons ... being unfair to blind the enemy, http://en.m.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Weapons
...

Everybody almost signed that Protocol (not that I claim to understand what a "Protocol" is), which is more than most other agreements, like ones banning landmines. However, the language is loose enough to allow many blinding laser weapons. If a "combat function" of the device is not to cause permanent blindness [no recovery possible], then the device is acceptable. IOW, if the combat function of a device is to cause less than permanent blindness, perhaps blindness for a day or so, then it's acceptable.
Certain systems are even designed to throttle back to come under the legal limit. The device measures the distance to the target (using a laser rangefinder) -> Considering atmospheric loses and distance, the power to the laser is adjusted to make the beam only temporarily blinding.


If you get caught, don't expect your enemies to be charitable.

 

[fechter]

I was commissioned by a neighbor to make another version of laser.
This one uses a NDB7A75 diode, which has a measured output of over 5W.


Power testing:


Here's a video:
https://youtu.be/FsBR3ZyX_YI
[youtube]FsBR3ZyX_YI[/youtube]

 

[oatnet]

Thanks Fechter, this thread is AWESOME!

-JD

 

[fechter]

I think I'm going to rebuild the Weller gun with a nicer looking housing and a better heat sink.
I've been thinking about features like a video camera coaxially mounted with the beam for aiming and a beam stabilizer (like optical image stabilization in a camcorder) to keep the beam from shaking. Auto focus would be nice too.

Here's a shot of the guts on the E-5:

 

[Drunkskunk]

Dude, that thing is just freaking amazing!

 

[megacycle]

So cool fechter.

 

[johnrobholmes]

Sorry I was right about the emitter failure :lol:


Sweet stuff! I just picked up a 50w CO2 laser cutter. Wish it was in the visible specktrum so I could be naughty and point it into the sky for a light show.

 

[fechter]

The blown diode was an educational expense. Also gave me an excuse to upgrade.

I have a 60w CO2 at work. In Ultra-pulse mode, it made a (tiny) hole all the way through a piece of 2x4 wood. It will make a mess of anything glass. In free beam mode, you can ignite a big spot on a piece of wood from across the room instantly. It's not so portable though.

I'm sort of eyeing the 60W diode fiber array package. With the right lens, it should be quite deadly at close range. That could possibly be hand held.

 

[Ykick]

W O W

 

[amberwolf]

W O W

Nah, they havent' been around for a while. But they did make the Laser Tag system...and there's an imaginative member here that was involved with that and "hordes" of other stuff.

 

[TheBeastie]

I have a bit of a dislike for lasers for the fear of going blind to them since a little incident I had a few years ago.

I remember walking down the street going for a decent walk down to the shops and something caught the side of my eye I turn to look up across the road at an apartment window and suddenly see a full red flash like I had stuck my face into a red traffic light stop for a second, it then shrinks to a spot as I see some one pointing a laser at me from the apartment window which is has its curtains fully drawn.
The person had moved away from the window as soon as he shined the laser at me knowing he had got my attention and I saw him move away.
This was during the middle of the day, it was a tad cloudy but still a decent bright day..

I am kind of stunned and angered. I then looked around for a rock on the road to throw through his window, I then look up again and I can't work out which window he shined the the laser at me from.
The road was 4 lanes wide (cars parked on each side) so it was a decent distance.

I then kind of just stood there and felt like a bit of a fool as there now wasn't much I could do. All I could think about was that was no normal laser and wondered if I had got some eye damage. I looked around and could still see so I just moved on with hesitation.

About a year later I went for my eye examination as I wear glasses and sometimes contact lenses. They used their fancy optometry gear and took a digital photo of the inside of me eyes which is common procedure at modern optometrists, the optometrist looked at the picture and said I had developed a spot in one of my eyes since my last eye exam. Said its nothing to be too worried about but it should be monitored, I asked whats the worse that could happen he quickly replied well if it grows it might be cancerous tumor and I would have to have my eye removed.
I recon it was that laser..

Kind of looks like this where you can clearly see a spot.. Something to think about for folk who don't take lasers seriously.

 

[Punx0r]

Lasers damage eyes by thermal effects, I'm not aware of any even theoretical link between that and cancer. Possibly the laser that was point at you was a regular <5mW laser pen. The lasers being discussion in this thread are ~10,000 times more powerful than that. Many also have the added bonus of an invisible beam.

Hopefully the experimenters in this thread are taking the proper safety precautions even though the safety issues hasn't been mentioned.

 

[fechter]

If you watch my video, you'll see I make a point about wearing safety glasses. High powered lasers can blind you faster than your eye can blink shut. Just like real guns, you have to be careful and responsible about what you aim at. There are formulas you can calculate the safe distance, etc. with.

For future builds, one feature I'd like is a video camera for the sight. The display screen can be in the path between spot and eyes to provide good eye protection.

 

[fechter]

Here's another one I recently built. This was made from an obsolete surgical drill and some bits and pieces from the junk box. It's only 50mW, so won't burn stuff, but is good as a prop gun or laser pointer. Someday I might decide to upgrade the power to something more dangerous.


Key switch is in the bottom of the grip



Beam shot at night:

 

[gammaray]

I have had zero success with anything that flies. I guess I need more power

The FAA would like to have a word with you...

In terms of actual science though, if you aimed a short pulse (50ms) at your hand, would it burn?

 

[fechter]

I have had zero success with anything that flies. I guess I need more power

The FAA would like to have a word with you...

In terms of actual science though, if you aimed a short pulse (50ms) at your hand, would it burn?

No, not at that power level. It's like passing your finger though a candle flame. Not enough time to heat the tissue.
I can't feel any heat at all with the 50mW beam. 5W will burn if the exposure is long enough (it would take several milliseconds).