A laser roulette pointing to the sky

Hi guys, I am new over here . Well, yesterday I was playing with my laser. It's a green cheap laser, but has enough power to be very noticeable when I point to the stars in the night. So after that I had an idea, what if you put four or more lasers on a roulette, and you spin it with a dc motor or a drill ? Will it looks like a very tall cylinder ? Has anyone done this ?




Update: I think that it would be better idea if we make a hole for each laser, so the roulette will be more stable and strong.

I guess if you get it fast enough. Id like to see that though. Would look neat regardless.

That's an interesting idea. Might have to try that out sometime soon; if only I had four identical greenies to experiment with!

You could do this fairly simply with a drill and some garage modifications.

Speedy78 said:

I guess if you get it fast enough. Id like to see that though. Would look neat regardless.

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I definitely want to give it a try, but first I am going to buy some cheap lasers at the one dollar store. I have planned pasting them onto my pedestal fan using hot glue, which is hard enough and easy to remove it. Then all I have to do is to make some smoke in order to make visible the laser beam. (I think I can use baby powder).

No, it won't look like a tall cylinder. It'll just look like a really fat and dim beam.

Wouldn't it be similar to a laser PJ doing those tunnel effects? Or is that due to the super fast galvos and you would be unable to produce that speed with a dc motor?

I get why you would think it works like that, but spinning actual lasers is a much more costly way of shooting lasers on to a spinning mirror.

Try this:
Glue a mirror on to an old PC fan or motor and shine the laser at the mirror from close USING EYE PROTECTION. Smoke a cigarette in the room or burn a little newspaper and turn the light off. You will be amazed

Alternatively, it'll be more stable for rotation and easier to adjust if you lay those lasers down on the disk and have them reflect upwards with a mirror at 45 degrees -- rather than the lasers themselves at the edge, facing upwards.

I think it could very possibly look quite bright as a single fat beam, if the disc is spun quickly enough. You'll be playing with human persistence of vision, and will need to take advantage of a "rotary" 'pulse width modulation' of sorts. (Totally different effect) But by spinning the array very quickly, the "duty cycle" of there being a beam in a single spot will help the illusion of the beam always being present in one vertical position along the disc's arc.

So... suppose you have 4 lasers on a circular disc. You'll need to return a green beam back to any given point point along the arc of travel, at least some ~30x per second.

So spin the spin a about 7.5 rps or 450 rpm to achieve this.

The larger the diameter of the disc, the fast the beams travel along the arc, and the faster their position changes in time. This may cause a sort of a better 'blur' effect. A smaller disc might be easier to spin so quickly, but the lasers will not achieve the same instantaneous tangential velocity - causing a better "duty cycle" but less travel through the air to "persist" vision with.

In my opinion - I think these two effects will ultimately cancel each other out to some effect. Go with whatever disc size you want to, as long as you can spin it at ~450 rpm or faster - safely.

BB's alternative method is a very good idea to consider. Mirrors would also allow for verrrrrry tight and precise beam position adjustments. Green DPSS lasers are not known for always being emitted perfectly straight out of the laser module. Modules can be made misaligned so long as they still put out a desired amount of power. So getting 3 axis screw adjustable mirror mounts will be a must.

Laser.....Disc....Glue.... Woah, this is getting complicated.

It is a neat idea though and am interested to see it done. GL

Rotating lasers like that will no nowhere near as bright as pointing a single beam in the sky, unless it's foggy. I've done similar with my 1.5W RGB projector and the beam is only just noticeable in the sky when scanned.

You should do what BionicBadger said and lay them on the disk and have them reflect up. Also, you should position the laser modules close to the center so as to reduce the moment of inertia. At those speeds you don't want the weight towards the outside of the disk. Also, having them closer to the center will reduce the velocity of the modules and hopefully will reduce the strain on the delicate DPSS system. You don't want to buy all these modules just to have them disassemble themselves from the "good vibrations" Also, I think it would look the best if all the modules were ~80-100mW. That way you get increased brightness to help make up for the persistance of vision mentioned earlier.

Looking forward to seeing this idea realized!
-Isaac