simple tester
A while back I was checking a lot of "found items" like mixing bowls and ladles, to make a reflector. I connected a 6 volt flashlight bulb with about 10 inches of solid copper wire, up to a battery holder with two 1.5 volt cells. When I throw the switch, the bulb lights up, but not too bright to look at.
To check a bowl with this tool, I put the bowl on a table, and then laid the battery & bulb assembly on some books next to the bowl, used some masking tape, etc., so the bulb is held at the center of curvature of the sphere. Then I would move my head around to see if the reflection of the filament came back to the filament. If necessary, I would adjust the position of the bulb slightly and then try again.
If you can find a position for the bulb where the reflection is right behind the filament when viewed from all directions, then you have found a good spherical object.
This is a good test, since this "reflection back to the light source" mode is exactly how you use a spherical reflector in a DIY projector.
A while back I was checking a lot of "found items" like mixing bowls and ladles, to make a reflector. I connected a 6 volt flashlight bulb with about 10 inches of solid copper wire, up to a battery holder with two 1.5 volt cells. When I throw the switch, the bulb lights up, but not too bright to look at.
To check a bowl with this tool, I put the bowl on a table, and then laid the battery & bulb assembly on some books next to the bowl, used some masking tape, etc., so the bulb is held at the center of curvature of the sphere. Then I would move my head around to see if the reflection of the filament came back to the filament. If necessary, I would adjust the position of the bulb slightly and then try again.
If you can find a position for the bulb where the reflection is right behind the filament when viewed from all directions, then you have found a good spherical object.
This is a good test, since this "reflection back to the light source" mode is exactly how you use a spherical reflector in a DIY projector.
Bodgy,
I thought you might repost the link using the http button...
Ill try to anwer from the specs you show.
No. The worst spec is the CRI of 65. This bulb will have a few colours that really spike and the rest will be very flat. It is possible that the spikes are at the 3 primary wavelengths of your lcd but that would be a real gamble.
Better to go with a 90+ cri bulb.
The 40mm arc wont be great either although if your lens and projector are BIG it wont be too bad. It really comes down to the angles.
I thought you might repost the link using the http button...
Ill try to anwer from the specs you show.
No. The worst spec is the CRI of 65. This bulb will have a few colours that really spike and the rest will be very flat. It is possible that the spikes are at the 3 primary wavelengths of your lcd but that would be a real gamble.
Better to go with a 90+ cri bulb.
The 40mm arc wont be great either although if your lens and projector are BIG it wont be too bad. It really comes down to the angles.
I have a m58 ballast i got for $30 .. 250 watt..... it seems like all the bulbs i can find for it are rated at 65 CRI. Are there any bulbs for the M58 ballast that has a higher CRI that anyone knows about?
Re: mirror versus white
My personal experience with mirrors under $100 is that they created bad hotspots. I've burned my plant because of a hotspot it created. Going by reflectance, you are right. But that isn't all we are trying to do, we also want to evenly distribute that light onto the fresnal. Right?
Now, if we were using the dual condensor lense way, we'd want to focus all the light into the first condensor to then have it distributed evenly by the second one throwing at the fresnal (which may even be optional depending on condesor quality.) With this, there will be no hotspots no matter what and the most-even distribution I think we will ever get. If I can find a large condesor around 8-10" diameter, (For under $50) I am going that route.
And yes, chrome has even lower reflectance then stainless and aluminum. I wouldn't be surprised if you could get aluminum to shine over 70% with the right kind of work.
Guy Grotke said:
My personal experience with mirrors under $100 is that they created bad hotspots. I've burned my plant because of a hotspot it created. Going by reflectance, you are right. But that isn't all we are trying to do, we also want to evenly distribute that light onto the fresnal. Right?
Now, if we were using the dual condensor lense way, we'd want to focus all the light into the first condensor to then have it distributed evenly by the second one throwing at the fresnal (which may even be optional depending on condesor quality.) With this, there will be no hotspots no matter what and the most-even distribution I think we will ever get. If I can find a large condesor around 8-10" diameter, (For under $50) I am going that route.
And yes, chrome has even lower reflectance then stainless and aluminum. I wouldn't be surprised if you could get aluminum to shine over 70% with the right kind of work.
Re: hooking up 2 ballasts together
I know it will for a fact, I have used powdercoating on automotive calipers before. They glow white hot and have even eventually taken out powder coatings. I know it stands up to at least 1500f and below fine, but over that don't bother.
DO NOT combine two MH ballasts!! If you are not sure about how they work, they start up with a 10-15k volt charge then continue at around 3000-5000 volts after they are started. Several amps of current is on tap, 2-3 amps can kill. Combining two would give you TWICE as much power on startup, at least guaranteed to shorten the bulb life. And be careful these can END YOUR LIFE if something goes wrong. I have been shocked by a 175watt MV setup and it nearly knocked me on my ***. My arm was numb for a week, if you do try this please read up as much as you can. This may be doable with some ballast wire swapping, I will try to look into this as well for you.
Dazzzla said:
I know it will for a fact, I have used powdercoating on automotive calipers before. They glow white hot and have even eventually taken out powder coatings. I know it stands up to at least 1500f and below fine, but over that don't bother.
juice_e said:
DO NOT combine two MH ballasts!! If you are not sure about how they work, they start up with a 10-15k volt charge then continue at around 3000-5000 volts after they are started. Several amps of current is on tap, 2-3 amps can kill. Combining two would give you TWICE as much power on startup, at least guaranteed to shorten the bulb life. And be careful these can END YOUR LIFE if something goes wrong. I have been shocked by a 175watt MV setup and it nearly knocked me on my ***. My arm was numb for a week, if you do try this please read up as much as you can. This may be doable with some ballast wire swapping, I will try to look into this as well for you.
bodgy said:
Let me lay this on the table, a Mercury Vapor lamp fits in our Metal Halide ballast socket and works perfectly WITH A SMALL arc gap! I am pretty sure they are all under 20mm. Take a look around and see if this would benefit you any more then a MH setup.
I just did some research, my 400watt MH ballast has a 4000-volt starting pulse and as far as I see (from other sources too) there is a 1:10 ratio on wattage to starting power with the MV/MH lights. HPS has a higher wattage starting pulse then any other does. (Didn't find exact numbers though.)
You must be thinking of silicon based powder coating to with stand that type of temperature. Any thing over about 500°C will cause organic pigments to deteriorate. Have you got a link to the type that you are referring to? The common thermo-type powder coating will not stand high temps.
I think that you will find that the operating voltage for MH lamps is around 90-150Volts. And yes it can still kill.
DJ
I am not an expert with this stuff, being a noob an all, but what about glass rod, like people make glass ornaments out of, surrounding the arc, and then bent towards a collector point and then melted together. Would this form a good light source or would it be k rap?. The thought occured to whilst making a shop light display using fibre optic light guide, in which i had 1 light source, but many fibre optic strands. In my thoughts you would end up with a single point light source, but can light be `bent` like this sucessfully?. What about glass cut to shape on the back and mirrored to reflect all the light back, or a lens which would be possibly a good shape, and that was mirrored on the curved side?
That would yield many point sources. Even bundling the ends together the light intensity will be decreased by the spaces between the fibers and the % lost getting it into the fibre in the first place.
You get a higher density light packing and a more efficient system with a elliptical reflector.
Dazzzla said:
500c is 932f, I know these lights don't get over 300C, I was simply saying I have seen powdercoating last on brake calipers that glow red/white hot which is around 1500f, which is past the operating range. I know this is not the working range desired, just saying that at that extreme temp it held up for much longer then I even thought it would, 3 months before any signs of serious wear. Not to mention it was touching and bonded to the actual hot surface, unlike a reflector. There are many cermic coatings that I have used that will withstand 3000f and one even operates at 5000f+ with no problems, but these are not the type of coatings I was talking about.
I know for a fact that the operating voltage for a 175watt MH bulb is about 330volts and appears to be fairly linear as you increase wattages of bulbs. (Almost a 2:1 watts to operating voltage ratio.) The starting voltage has the most current and the most voltage. (5000volts and 4-AMPS on JUST a 175watt ballast!) The imporatant part that I am trying to get through is that it's the current that kills people. Obviously the higher the voltage, the more likely it is that it can shock and kill you as it increase the potential for arcing. If you feel like hurting, try this, touch the positive and a ground, or just get a few mm from each one, it will shock the living hell out of you!
Me2! said:
Sorry, no bad intentions, I figure people on here to have 100+ IQ's and to understand it as a joke. (Can I say "If they were dumb enough to try such a thing, we're better off without em?") I think we ALL know electricity is deadly!
Honestly, thanks for the concern though. I'll be more careful.
Me2! Would this shape work to focus the light, or would this again give multiple light images, cos this was the principle that I was thinking of. It would prolly be too expensive to produce, the heat may fracture etc, but it would look good if it worked. and yes I know I spelt Hole wrong!. The glass would `in theory` work as a light guide.
Attachments
Yes low voltage and amperage can kill. On tv, mythbusters showed that the body can endure extreme high voltage, whereas if the voltage is sufficent, and the amperage is 30ma (yes just 30ma), that is enough to kill, in relation to where the electricity enters the body. ie if the electricity enters thru fingers and exits futher up arm, you will get shocked and withstand a greater potential. if it enters thru fingers and exits thru toes then it goes past or thru the heart, which is stimulated by minute electrical pulses. I would also ask a moderator to edit this post saying to deliberatly arc two wires together. Thats how accidents happen. Mind you, they would be up for a darwin award!!
The same solid light guide has occured to me and probably everyone who has spent time trying to figure these things out. Basically a fat fiber optic idea. I dont know if it would work you would have to ask a physicist. It's a light guide. This falls into the realm of non-imaging optic theory which is a huge topic. Its study would take you far away from projectors.
Problems i see would be material purity, cost of manufacture.
anyone else got thoughts on this?
Problems i see would be material purity, cost of manufacture.
anyone else got thoughts on this?
As I understand it, that teardrop shape would work well for concentrating a jet of liquid, but would not work for concentrating a beam of light. It's apparently impossible to concentrate a beam of light in that way.
Basically, you can't reduce the cross-section of a lightbeam without increasing its divergence-angle.
With that teardrop shape, we'd be trying to reduce the cross-section from the circumference of the lamp arc (white circle) to the smaller nozzle tip... ~5? times smaller (*)... , AND reducing the divergence angle from 360 degrees to the angle of the teardrop... ~20 times smaller? Apparently this is impossible.
Even as I write this, I think it must be possible. I mean, a bulb in a mirrored box with a small hole in it... all the light must eventually come out the hole, right???! I just tried it in a ray-tracer, and yes eventually all the light comes out (some after 100 reflections)...
Yet from what I've learned in theory:
- A beam of light from the sun has very small divergence angle. One can focus that beam's cross section to a very small area, using a lens... but, the divergence-angle will increase by at least the same factor.
OR
- A light bulb filament represents a small cross-section, but large divergence angle (it sends light in all directions). One can decrease the divergence angle, using a deep parabolic reflector... but, one will find the beam's cross-section has increased by at least the same amount.
OR (more obviously)
- One can decrease cross-section and divergence-angle, using an iris / aperature... but the lumens will decrease.
The basic principle is known as http://www.google.com/search?q="conservation+of+etendue"
(*): liberty taken, measuring in 2D instead of 3D
If someone could relate this to the current LED -array discussion, that would be great.
Basically, you can't reduce the cross-section of a lightbeam without increasing its divergence-angle.
With that teardrop shape, we'd be trying to reduce the cross-section from the circumference of the lamp arc (white circle) to the smaller nozzle tip... ~5? times smaller (*)... , AND reducing the divergence angle from 360 degrees to the angle of the teardrop... ~20 times smaller? Apparently this is impossible.
Even as I write this, I think it must be possible. I mean, a bulb in a mirrored box with a small hole in it... all the light must eventually come out the hole, right???! I just tried it in a ray-tracer, and yes eventually all the light comes out (some after 100 reflections)...
Yet from what I've learned in theory:
- A beam of light from the sun has very small divergence angle. One can focus that beam's cross section to a very small area, using a lens... but, the divergence-angle will increase by at least the same factor.
OR
- A light bulb filament represents a small cross-section, but large divergence angle (it sends light in all directions). One can decrease the divergence angle, using a deep parabolic reflector... but, one will find the beam's cross-section has increased by at least the same amount.
OR (more obviously)
- One can decrease cross-section and divergence-angle, using an iris / aperature... but the lumens will decrease.
The basic principle is known as http://www.google.com/search?q="conservation+of+etendue"
(*): liberty taken, measuring in 2D instead of 3D
If someone could relate this to the current LED -array discussion, that would be great.
Hi Charlie,
Thats not the whole story. What you say seems true in standard optics theory.
When I thought up the same thing he drew I researched it for a few days before I gave up on it and there are 2 fields, one you have discussed (also see the Feynman Lectures for a good discussion of it) and the non-imaging optics field.
http://hep.uchicago.edu/solar/NIoptics.html
This is a nice summary:
I gave up on it for practical reasons -cost- not because its not viable.
Thats not the whole story. What you say seems true in standard optics theory.
When I thought up the same thing he drew I researched it for a few days before I gave up on it and there are 2 fields, one you have discussed (also see the Feynman Lectures for a good discussion of it) and the non-imaging optics field.
http://hep.uchicago.edu/solar/NIoptics.html
This is a nice summary:
I gave up on it for practical reasons -cost- not because its not viable.
Having started this I soon realised one very important fact. The lamp would have lots of reflected IR, which in turn would overheat the bulb glass, which would in turn lead to failure of the bulb. It was a nice thought whilst it lasted, but you watch some clever person will build it and suceed. If it was to be built, the best place to get some idea of price would be at a glass blower, or some clever Italian in Murano, whom could prolly do it cos when I was in Venice 2 years back, they were producing some VERY similar looking bits of kit
And if this would not work according to the theories above, then can someone explain how it works for a condenser lens, or am I missing something here?
Nothing is impossible, just Improbable!
And if this would not work according to the theories above, then can someone explain how it works for a condenser lens, or am I missing something here?
Nothing is impossible, just Improbable!
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