CGW search light on the clouds...

[Dan Goldstein]

Ok, I am working up plans for CGW search light on the clouds Beta test 0.2 .
0.1 test for all that missed it:
https://www.facebook.com/photo.php?fbid=10150305995609999&set=a.10150305995594999.1073741827.66061899998&type=3&l=667fe196da&theater
(Nice picture, not sure who took it.)

Does anyone happen to have a 1000W pulse start Metal Halide Lamp
Balast they want to donate to the project?
120V if possible.

Carbon arc is cool, but the efficiency is about 7-8 lumens per watt.
Metal Halide is
near 100 Lumen per watt. So is LED but to get up to the range of
100,000 lumens it would take a large cluster of 200X5w leds and the
focusing issues would kill you. As would the cost...
So Metal Halide seems like the best technology to go with for now.
Anyone know more about this and have suggestions?

As always this is just for Grins and Giggles.
But it does seem like world domination would be just a little easier
if we could project our CGW/Dragon head on the sky at night to strick
fear in
rival roaming hacker spaces...

Dan

PS Yeah too much. or not enough coffee...

--
"There is nobody in this country who got rich on his own. Nobody. You
built a factory out there - good for you.

But I want to be clear. You moved your goods to market on the roads
the rest of us paid for. You hired workers the rest of us paid to
educate. You were safe in your factory because of the police forces
and the fire forces that the rest of us paid for. You didn't have to
worry that marauding bands would come and seize everything at your
factory...

Now look. You built a factory and it turned into something terrific or
a great idea - God bless! Keep a big hunk of it. But part of the
underlying social contract is you take a hunk of that and you pay
forward for the next kid who comes along."
- Elizabeth Warren (Sept. 2011)

[Tipton, Peter A.]

Dan,

Would it be possible to focus the light such that it could be used to heat
sand and make glass? A quick search of the web suggests that could be
accomplished at 2700 F (with proper additives). How cool would that be?

Peter

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[Scott Kovaleski]

As a matter of fact Dan, I spent my first year after graduate school as a High Intensity Discharge Lighting Engineer/Scientist at General Electric Lighting. So I do know a little about this. Imagine that.

Good point about lumens per watt. Your numbers are accurate to an order of magnitude. A lot of nifty thermochemistry goes into getting as many lumens per watt as possible out of a QMH or CMH lamp. LEDs suck for this application: not only do you need a lot of LEDs to get enough lumens, but they will be distributed over a panel, which makes for bad imaging. Ideally, you want a very very intense point source of light.

They make quartz metal halide and ceramic metal halide lamps from less than 100W to 1500W. The most expensive piece of the puzzle is the ballast, which will be several times the cost of the lamp. I know you could at one time by 400 W lamps at Home Depot, probably ballasts as well. A 400W lamp from GE would give you a lot of lumens. You can also buy parabolic reflectors for these lamps with integrated lamp sockets, which is handy.

Something to keep in mind is that these babies will make it very warm near them. Having a housing that can handle the heat is important.

[Matthew Little]

I may have access to a parabolic reflector designed for industrial lighting - I'll see if I can dig it out by tomorrow and bring it so we can see if it will work.

[Dan Goldstein]

For melting the Carbine arc is the thing to use. More heat, less light.
But, even cooler would be an induction furnace. Coil of copper tubing
with cooling water going though it and a AC current through it to
produce an oscillating magnetic field. Induces a current in a steel or
iron mandrel to heat it up. Is the melting temp of steel less than
Glass.. No, But...
I found a cool link that points out that glass becomes conductive at
high temperatures. So, if you pre-heat it you can then use an
induction coil to melt it! Ok I am sure there are many details to work
out,
but a cool idea... You guys keep getting me off on these wonderful tangents...
See: http://www.fivesgroup.com/FivesCeles/EN/Expertise/InductionApplications/Pages/Glass-Melting-and-Direct-Coil-Induction-Heating.aspx

Dan

[Ryan Raney]

Look up the video of melting a glass bottle in a microwave. Preheat a spot with a blowtorch and put the bottle in.

[Dan Goldstein]

Matthew, looking forward to see what you dig up, Thanks..

Scott..
I am starting to look for used ballasts. I found this:
http://columbiamo.craigslist.org/grd/3812162499.html
I was hoping to find something cheaper, maybe pulse start (a bit more
lumens correct?)
Electronic?

I think I have a line on a large projection TV fresnel lens. If I can
get it, and we can keep it cool(!) enough, I would like to design a,
spherical reflector system, that focuses back to a point right next to
the bulb, and then both "near" sources shine through the fresnel lens.

Or maybe an ellipsoidal reflector? Thoughts from your experience?
Dan

On Wed, May 22, 2013 at 9:16 AM, Scott Kovaleski
<scott.k...@gmail.com> wrote:

[Dan Goldstein]

very cool
http://www.youtube.com/watch?v=RYdaYQuEhy4

So this *should* work for sand also...
A little preheat with a torch. But you want to be careful as the
microwave tray is glass.
I guess it works as long as it does not heat up too much? Or maybe it
is pyrex or something like it...

Anyone game to try it?

[Scott Kovaleski]

If you are projecting a shadow image over a large distance, I think you want a parallel beam from a point source of light. I think you get that with a parabolic reflector. Spherical reflectors make images, as would the fresnel lense. I don't know if you could make the image distance far enough away, and then I am not sure about the magnification.

That 1000W lamp won't be a great point source of light, as the arc is probably 5 inches long or something. I believe that is a pretty inexpensive price for a ballast, however.

[Dan Goldstein]

Good points.
A parabolic reflector will produce parallel light using the portion of
spherical light source (assuming point source for now) that hits the
reflector. 30-40%? Depends on the size of the reflector and the
focal distance.
being a perfectionist, I was looking at setups that can focus more of
the spherical light source in a parallel beam. The spherical reflector
with a fresnel (or regular) focusing lens potentially can
capture much more of the spherical light source.
But reality sets in and I do not know yet how all the real world
factors effect the efficiency.
The bulb is not point source as you point out. The spherical reflector
cannot focus on the exact location of the source so that spreads the
effective source for the lens even more.
Also the fresnel lens is not perfect (the ones I can get far far from perfect).

So from your experience how close in over all light capture to a
paralel beam are the two systems?

I don't understand your comment: "Spherical reflectors make images, as

would the fresnel
> lense. I don't know if you could make the image distance far enough away,
> and then I am not sure about the magnification."

I have experimented with a small fresnel lens and a pseudo point
source (LED array).
I could get a nice parallel beam, although it was more rectangular
because the source was rectangular. I was hoping for the same effect
with a larger fresnel lens and the larger bulb.

[Matthew Little]

While we're on the subject of optics and lenses and reflectors and all that jazz, do you guys have any recommended resources for learning more about this kind of stuff?

[Scott Kovaleski]

There is a textbook by Hecht that is pretty clear on the subject. I don't recall that you need calculus or anything to understand it either.

The other option is that your local hackerspace accepts the idea of doing some optics related co-learning/instruction on a topic of interest to several...

[Scott Kovaleski]

Dan,

The amount of light you collect is related to the area of the optic and your distance from it. That parameter is related to the f/# IIRC, and might be the numerical aperture. IIRC, a point source at the "focus" of a parabolic reflector makes a parallel beam, which would be a good backlight for the shadow mask. I think you could bring 50% or more of the light into a beam if you had a good point source and a good reflector. If you use a lens to make an image of the shadow mask, you backlight the shadow mask, which is a some distance beyond the focal point of the lens, and it will make an image some distance away, governed by the thin lens eqn:

d_object^-1+d_image^-1=focal_length^-1

with magnification

d_image/d_object

So if you want your object distance far away, magnification gets very big, and your object gets very close to the focal point. Your light source is further away than the focal point as well, so that reduces your light collection. That was were I was coming from with imaging (using spherical lenses/reflectors). An image formed this way will look very good, but probably not have a lot of light on it.

You could use a lens to make a parallel beam by putting a point source at the focal length (d_image = infinity) which might work, but even with a really big fresnel lens and a really short focal length, something less than 50% of the light is collected, unless the spherical reflector puts the all of the backward rays right back through the focal point. Note you are still making a image of the small part of the lamp that is right at the focal point. Anything outside the focal point lost (or rather, imaged somewhere and then lost). That still requires a very big spherical reflector with a short focal length exactly matched to the focal length of the fresnel lens. What is sometimes done is to make a parallel beam first (say using a parabolic), use a focusing lens to put all the light through the focal point of an downstream objective lens. At the focal point, you can use an aperture to "clean up" the beam, and then make a parallel beam with the last lens.

I thought for projection, we were going to backlight a cutout and project a long way away. So I figured the simplicity and imaging characteristics of the parabolic reflector backlighter made the most sense. That is not to say the large fresnel lens aren't useful and interesting, I just didn't figure they were best in this case.

[Chad LaFarge]

What was that middle part, again?

 

Chad

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>> > --
>> > "There is nobody in this country who got rich on his own. Nobody. You
>> > built a factory   out there - good for you.
>> >
>> > But I want to be clear. You moved your goods to market on the roads
>> > the rest of us paid for. You hired workers the rest of us paid to
>> > educate. You were safe in your factory because of the police forces
>> > and the fire forces that the rest of us paid for. You didn't have to
>> > worry that marauding bands would come and seize everything at your
>> > factory...
>> >
>> > Now look. You built a factory and it turned into something terrific or
>> > a great idea - God bless! Keep a big hunk of it. But part of the
>> > underlying social contract is you take a hunk of that and you pay
>> > forward for the next kid who comes along."
>> > - Elizabeth Warren (Sept. 2011)
>> >
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>> >
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>> --
>> "There is nobody in this country who got rich on his own. Nobody. You
>> built a factory   out there - good for you.
>>
>> But I want to be clear. You moved your goods to market on the roads
>> the rest of us paid for. You hired workers the rest of us paid to
>> educate. You were safe in your factory because of the police forces
>> and the fire forces that the rest of us paid for. You didn't have to
>> worry that marauding bands would come and seize everything at your
>> factory...
>>
>> Now look. You built a factory and it turned into something terrific or
>> a great idea - God bless! Keep a big hunk of it. But part of the
>> underlying social contract is you take a hunk of that and you pay
>> forward for the next kid who comes along."
>> - Elizabeth Warren (Sept. 2011)
>>
>> --
>>
>> ---
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--
"There is nobody in this country who got rich on his own. Nobody. You
built a factory   out there - good for you.

But I want to be clear. You moved your goods to market on the roads
the rest of us paid for. You hired workers the rest of us paid to
educate. You were safe in your factory because of the police forces
and the fire forces that the rest of us paid for. You didn't have to
worry that marauding bands would come and seize everything at your
factory...

Now look. You built a factory and it turned into something terrific or
a great idea - God bless! Keep a big hunk of it. But part of the
underlying social contract is you take a hunk of that and you pay
forward for the next kid who comes along."
- Elizabeth Warren (Sept. 2011)

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