Cheapest RGV laser?

[florian]

Hi everyone,

I need 50 RGV lasers (3 * 5mW) for an art installation, for less than $40 each ($2000 total ).
I now I can make them myself like c4r0 did (http://laserpointerforums.com/f40/my-rgb-laser-44138.html, I found some yellow and cyan dichroic filters on ebay) for around $20, but I am really surprised I can't buy a module already done like that.

Does anyone know if/where I can find a cheap low-intensity prebuilt RBV laser module?

Thanks a lot,

 

[Pontiacg5]

Re: Cheapest RBV laser?

I hate to break the bad news, but that is really not going to happen at those prices. Sure the materials would probably be around $40, but it takes a pretty long time to align all those beams. Unless you find someone willing to work for free I think you might need to increase your budget or settle.

 

[kiyoukan]

Re: Cheapest RBV laser?

well it depends on alot of factors.
if you know a contractor in mexico maybe but anywhere else its going to cost a bit more.
first off you need to drive the lasers and considering its for art you will want more than 7 colors you will want an analog driver those are around 15$ each.
also do you need perfect beam alignment or just enough?
we would need alot more details to better help you.
also at those low powers the only thing you will see is green. for every 1mw of green it takes 5-7mw of blu-ray and 4mw of red.
So you are looking at around just in lasers 35-40$
then you can use the some of the parts from the blu-ray laser to mix all the colors.
So you will have no need for dichroic filters.
not cheap and not prebuilt, are you sure you can use some well focused leds?
i have got an led to have a 3 in dot at around 20-25ft.
much cheaper and they come in RGB, so no fancy optics or anything needed.
well okay there are a few fancy optics but they are about 9$ each and then another one for 5$. one is a fiber optic coupler.
i have gotten it so focused i could see the dye on the wall.

 

[florian]

Re: Cheapest RBV laser?

Thanks a lot for your help,

Here is a more thorough description of my project: http://laserpointerforums.com/f67/fpga-drive-50-rgv-lasers-scanners-55611.html

1) About the power:
the lasers are to be seen 1000 feet away in the dusty air of the desert. BUT the lasers will move pretty slowly, with the laser beam always clearly defined. I had 5mW R, G and V laser this year at Burning Man: the green was more powerful that what I need, the red was OK, and of course the violet needed to be around 5 times brighter.

2) About the alignment:
I totally understand that 1000 away it's a crazy precision that I would need to have, and it's not realistic. Let's say I would like the beam to still seem pretty grouped together at 30 feet. Is it more doable?

3) About the colors:
What does exactly an analog driver do? Does it reduce the voltage/current sent to the laser? Does it do some PWM? Or is there another element that dims the laser?
Can I achieve the same result as an analog driver with an FPGA?

 

[HIMNL9]

Re: Cheapest RBV laser?

About the powers: the apparent difference in luminosity of your 5mW lasers is due to eye srnsitivity curve ..... the green is in the region of the maximum sensitivity, so it appear much more bright of all the others, the red is on one end of the "bell curve", and you may need 2 or 3 times the green in power (depending from the mixing type you want to obtain), for have an apparent luminosity like the green one, and for the BR (violet, that is near UV range), it's on the other side of the curve, and in a region where the eye is also less sensitive than red, so for the same mixing type you can need from 4 to 5 times the power of the green (indicative values, cause the exact amount of powers depend from the color temperature that you want to obtain as "white point"

About the alignment: if you need so much units with the same characteristics, the only way i can imagine is to get parts worked from a CNC center or some factory that have a CNC machine available ..... but, usually, those works are all except cheap ..... they probably need to convert your draws in CNC program, or project something specific for you, if you still don't have draws, then set up the machine and produce the parts ...... this can end in hundreds of $$$ just for the production of the bodies, not speaking about the assembly and alignments .....

About the analog driver: it's simply a current regulated driver that you can drive with an analogic signal (a variable voltage from a potentiometer or a PC interface or similar), and can give you a proportional current, so you can change the output power of your laser from a wide range of values, instead just on and off ..... need to note that also for them are needed some more works than bare assembly ..... you need to balance all he drivers for minimum and maximum currents (based on your driving voltage), and ofcourse each laser need to be balanced, if you want that all them appears identicals (or the more similar possible), and all this add time, work and money .....

It look as an interesting project, but, for sure, not cheap .....

 

[Benm]

Re: Cheapest RBV laser?

2) About the alignment:
I totally understand that 1000 away it's a crazy precision that I would need to have, and it's not realistic. Let's say I would like the beam to still seem pretty grouped together at 30 feet. Is it more doable?

Overlap at 30 feet is perfectly doable, but not on a $40 budget. You need at least 2 completly adjustable mounts to make it work properly. You could suffice with 3 axes mounts if the dichro's are large enough and/or you manage to put the mounts in the right position, but thats about it.

Consider this: if your alignment is off 1 degree, the spots will be 17 centimeters apart at 10 meters distance. Practically you need to adjust the dichro's to 0.1 degree accuracy in both vertical and horizontal direction, and to within a milimeter or so in position.

How c4r0 managed to get it aligned just like that is a mystery to me - perhaps its possible using light sensitive epoxy so you have time to align things, and then fixate the position by irradiating it with UV to set.

All the basic components required can be found in the PHR803 sled that also has a weak red diode in it, which could be usable in your project. Considering those sleds go for under $10, i'd buy a couple to experiment with the optics: there is the turning mirror and a combiner cube for red and bluray inside. With a cheap green, 2 aixiz modules and simple drivers for red and bluray it'd be within the $40 budget, but you'll be tinkering with the optics for hours on each unit

 

[florian]

Re: Cheapest RBV laser?

All the basic components required can be found in the PHR803 sled that also has a weak red diode in it, which could be usable in your project. Considering those sleds go for under $10, i'd buy a couple to experiment with the optics: there is the turning mirror and a combiner cube for red and bluray inside. With a cheap green, 2 aixiz modules and simple drivers for red and bluray it'd be within the $40 budget, but you'll be tinkering with the optics for hours on each unit

Ok got it. I just ordered two PHR803. I will play with them and do my homework

 

[kiyoukan]

Re: Cheapest RBV laser?

come to think of it why take the red and the blue out of their heatsinks?
if he running them at that low power i think that he should be able to leave them their.
But you will have to find a way to put a lens on it but it will save you alot of time.
then you only have to align 2 laser instead of 3 right?
i could be wrong but that my thoughts.

 

[florian]

Re: Cheapest RBV laser?

About the alignment: if you need so much units with the same characteristics, the only way i can imagine is to get parts worked from a CNC center or some factory that have a CNC machine available ..... but, usually, those works are all except cheap ..... they probably need to convert your draws in CNC program, or project something specific for you, if you still don't have draws, then set up the machine and produce the parts ...... this can end in hundreds of $$$ just for the production of the bodies, not speaking about the assembly and alignments .....

So I hope to find some general aluminium bodies that I will machine myself. I will look around to see how people do custom made positioning system (with screws, maybe with sliders?) and try to come up with some creative cheap good-enough solution (I am OK to accept that I cannot do a very precise job with 50 units).

About the analog driver: it's simply a current regulated driver that you can drive with an analogic signal (a variable voltage from a potentiometer or a PC interface or similar), and can give you a proportional current, so you can change the output power of your laser from a wide range of values, instead just on and off ..... need to note that also for them are needed some more works than bare assembly ..... you need to balance all he drivers for minimum and maximum currents (based on your driving voltage), and ofcourse each laser need to be balanced, if you want that all them appears identicals (or the more similar possible), and all this add time, work and money .....)

OK, I will keep the analogic driver in mind when designing my custom driver board.


Also, does anyone see any issue with having an open-loop system with 1.8° stepper motors? What are my chances to have a position out of sync with what my controller thinks? (I guess the risk gets bigger with the motor speed)

 

[kiyoukan]

Re: Cheapest RBV laser?

you its called miss stepping. and it happens
i have a self made cnc machine that use similar motors to the ones you posted just a bit bigger and every few times i have to go and re adjust the motors. but its only a few degrees off less than 10 normally but.
also this happens most often when you go from a fast forward to a fast backwards.
you want a pause in between to stop the motion or else you increase you risk more.

 

[Pontiacg5]

Re: Cheapest RBV laser?

I work at a machine shop and I cold probably make whatever it is you are looking for, especially if you need 50 or so. I work pretty cheap

 

[florian]

Re: Cheapest RBV laser?

you its called miss stepping. and it happens
i have a self made cnc machine that use similar motors to the ones you posted just a bit bigger and every few times i have to go and re adjust the motors. but its only a few degrees off less than 10 normally but.
also this happens most often when you go from a fast forward to a fast backwards.
you want a pause in between to stop the motion or else you increase you risk more.

So I really may need an encoder on the motor if I want the laser to move fast right?

 

[florian]

Re: Cheapest RBV laser?

I work at a machine shop and I cold probably make whatever it is you are looking for, especially if you need 50 or so. I work pretty cheap

What could you do? The bodies in aluminium and the placement of the components?

 

[Benm]

Re: Cheapest RBV laser?

come to think of it why take the red and the blue out of their heatsinks?
if he running them at that low power i think that he should be able to leave them their.

I suppose that could work, although i've never tried to fire up both diodes in the sled to see how the beams are combined.

 

[HIMNL9]

Re: Cheapest RBV laser?

come to think of it why take the red and the blue out of their heatsinks?
if he running them at that low power i think that he should be able to leave them their.

You probably still need to realign or readapt them, for get the better pass-through and summing.

I mean, usually, at the end of the optics of a sled, you are lucky if you get 20% of the total power that the diode originally emits, and not just for the optics ..... also if you take away the diffraction gratings, the circular diaphragms and the correction lenses, the diodes are aligned with the PBS too far from the cube, for have a good coupling, so you still loose approximatively 40 to 50 % of the power just from this ..... maybe finding lenses small enough to fit inside the space occupied from the diffraction gratings, and placing them in the way that they can pre-focus the diodes, can help making pass through the cube some more power, but til now i've not found similar lenses, so mine is just a theorical speculation, til now .....

 

[Pontiacg5]

Re: Cheapest RBV laser?

What could you do? The bodies in aluminium and the placement of the components?

Yep, depending on which way you choose to go I could make the diode/module mounts, optics mounts, and the case that holds them all together.