what type of bulb are you using in that setup? The only similar lamps that I could find were 150w and I could never find the ballasts for them. I'd appreciate your help. Thanks!
I think there may be an issue with using only one half of a fresnel...
the focal length of a single half of a fresnel lens probably doesn't allow for this configuration. Recall that the fresnel lens focal length has to roughly match the focal length of the objective lens that you are using. I suspect that if you do things this way, the light will converge onto a space that is way beyond the objective lens - if it even converges at all.
Having said all of that, I agree with you that our light engine is still inefficient. Adding an "okay" reflector was the first step to improving it; then adding a good condenser lens helped a little, but now I think it's time to go back and find a different reflector. I'm currently working with a manufacturer to see how much it would cost to have one made that would work with the condenser lens in a much more efficient system. I fear that it wouldn't be cheap, so nothing may come of this. For the meantime, the soup ladle reflectors really do work pretty well. No matter what we do, we'll never have 100% efficiency - I assume that theoretically we can't even come within about 20% of that, but losing only 40% of our initial light really isn't too bad!
I think there may be an issue with using only one half of a fresnel...
the focal length of a single half of a fresnel lens probably doesn't allow for this configuration. Recall that the fresnel lens focal length has to roughly match the focal length of the objective lens that you are using. I suspect that if you do things this way, the light will converge onto a space that is way beyond the objective lens - if it even converges at all.
Having said all of that, I agree with you that our light engine is still inefficient. Adding an "okay" reflector was the first step to improving it; then adding a good condenser lens helped a little, but now I think it's time to go back and find a different reflector. I'm currently working with a manufacturer to see how much it would cost to have one made that would work with the condenser lens in a much more efficient system. I fear that it wouldn't be cheap, so nothing may come of this. For the meantime, the soup ladle reflectors really do work pretty well. No matter what we do, we'll never have 100% efficiency - I assume that theoretically we can't even come within about 20% of that, but losing only 40% of our initial light really isn't too bad!
The bulb is a cdm-t 150W, it´s equal to a HQI-T 150W, but you can also find HQI-T 250W in the same size, but they are pretty new once.
I have measured the focuspoint of the splited fresnellens, and it´s the double the orginallens. The design works very good so the 1/2 fresnellens do it´s work. But it´s important to turn it right. Another thing I have noticed is that I can´t see a singel circle from the fresnell that I did before.
I have measured the focuspoint of the splited fresnellens, and it´s the double the orginallens. The design works very good so the 1/2 fresnellens do it´s work. But it´s important to turn it right. Another thing I have noticed is that I can´t see a singel circle from the fresnell that I did before.
More information on the PAR30 design
I maybe need to give you more information on the PAR30 light engine design. To get this thing to work, you can NOT use whichever you like of the two half splited fresnellens. It must be the half close to the bulb, that half have a focal length that will fit the objectlens exactly (you can have the objectlens at exactly the same place as before.). To get the best picturequality you have to turn the fresnelhalf around, the grooves must be towards the bulb, otherwise you get rainbow pattern at the edges.
The reflector I´m using is from a PAR30 halogenbulb 75W (OSRAM), it must be the 30 degrees version. You don´t have to use the coollight version, the normal version of the bulb is much cheaper, but the lcd will get hotter, but try the cheaper first, it can be a bit tricky to cut it right the first time.
An other thing, don´t use a condeserlens with this design, it will never work, condensers collect light, we need to spread it, with this reflector design.
This PAR30 design is my final design after 3 years work with home made projectors, and I don´think it´s possible to get more light from the bulb, than this will give you. Those PAR30 reflectors are done professional and done to give as much light as possible from the bulb, they are also made to spread the light even on a surface. I hope you all try this design, it will give you a nice boost in brightness.
I maybe need to give you more information on the PAR30 light engine design. To get this thing to work, you can NOT use whichever you like of the two half splited fresnellens. It must be the half close to the bulb, that half have a focal length that will fit the objectlens exactly (you can have the objectlens at exactly the same place as before.). To get the best picturequality you have to turn the fresnelhalf around, the grooves must be towards the bulb, otherwise you get rainbow pattern at the edges.
The reflector I´m using is from a PAR30 halogenbulb 75W (OSRAM), it must be the 30 degrees version. You don´t have to use the coollight version, the normal version of the bulb is much cheaper, but the lcd will get hotter, but try the cheaper first, it can be a bit tricky to cut it right the first time.
An other thing, don´t use a condeserlens with this design, it will never work, condensers collect light, we need to spread it, with this reflector design.
This PAR30 design is my final design after 3 years work with home made projectors, and I don´think it´s possible to get more light from the bulb, than this will give you. Those PAR30 reflectors are done professional and done to give as much light as possible from the bulb, they are also made to spread the light even on a surface. I hope you all try this design, it will give you a nice boost in brightness.
why not use 100w par lights?
Using a parabolic lamp (PAR) has been in my mind for some time now. Only the heat i think in a normal par would be a problem. BUT i found a site: http://www.lampbrokers.co.nz/parpdr.html which cleams to have a halogen par lamp which can be build into a enclousure. The 100watt version give's off 10.000 focused lumen, which is enough i think for a 7" projector. I could not find a price yet. Could this be an option for a light source?
What about the new MH PARs? to expensive?
Using a parabolic lamp (PAR) has been in my mind for some time now. Only the heat i think in a normal par would be a problem. BUT i found a site: http://www.lampbrokers.co.nz/parpdr.html which cleams to have a halogen par lamp which can be build into a enclousure. The 100watt version give's off 10.000 focused lumen, which is enough i think for a 7" projector. I could not find a price yet. Could this be an option for a light source?
What about the new MH PARs? to expensive?
I used a 100W halogen PAR bulb in my first projector, with a 5" TFT 3 years ago, but one day I droped it in the floor and it was dead, but a can tell, it was good that I droped it, because I almost burned up my 5" TFT with that bulb. So if you are going to use it try the coollight version, that will maybe save your lcd. But anyway I don´t think the light output will be enough from that 100W bulb. If you replace the small halogen-thing in the middle of that bulb and place a 150W HID/HQI-bulb there instead you get 8 times more light !
Re: why not use 100w par lights?
I'm working on finding 250 watt mini MH lamps that would work in such a reflector. Also I know of some different manufacturers that make the reflector with any spot angle you wish, so it wouldn't be necessary to chop a halogen reflector and risk breaking it, nor would you need to place the lamp far from the fresnel unless you needed to. The only problem right now with these 250 watt MH lamps is finding a supplier. I can get plenty of the 150 watt kits if anyone wants them, but I really want to get the 250 watt babies - those things would be BRIGHT and without much heat (because they are metal halide instead of halogen and because the reflector can be a cool reflector as Mathias mentioned).
Also, about reflectors for a moment, I've determined that a spherical reflector is ideal for double-ended lamps if at all possible. I will have a diagram about this on my website in about a week (too many things to do right now), but I really do feel strongly that spherical is the way to go.
The Alchemist said:
I'm working on finding 250 watt mini MH lamps that would work in such a reflector. Also I know of some different manufacturers that make the reflector with any spot angle you wish, so it wouldn't be necessary to chop a halogen reflector and risk breaking it, nor would you need to place the lamp far from the fresnel unless you needed to. The only problem right now with these 250 watt MH lamps is finding a supplier. I can get plenty of the 150 watt kits if anyone wants them, but I really want to get the 250 watt babies - those things would be BRIGHT and without much heat (because they are metal halide instead of halogen and because the reflector can be a cool reflector as Mathias mentioned).
Also, about reflectors for a moment, I've determined that a spherical reflector is ideal for double-ended lamps if at all possible. I will have a diagram about this on my website in about a week (too many things to do right now), but I really do feel strongly that spherical is the way to go.
I agree with Diylabs on the fact of the double-ended lamps, the only way to use them is with the ohp-design, but again, you loose much light, as the picture below show.
What I wanna say is that you will get the same light output from the projector with a 150W 1-ended bulb in a PAR-design, as you get with a 250W double-ended in a ohp-design. Because the 150W bulb is much cheaper, here in Europe anyway, there is no point using a double ended bulb, but if you already have a double ended, keep using it.
250W 1-ended bulb, is availible here in Europe as MSD250 Philips and HSD250 Osram. But if you can find them in USA I don´t know.
Also, do you think you can get a manufacturers that makes the reflector with a 90 degrees angle, because that´s what we need if we don´t want to move the lamp backwards. The widest angle I have seen is 60 degrees, there must be a reason why they don´t make it wider.
What I wanna say is that you will get the same light output from the projector with a 150W 1-ended bulb in a PAR-design, as you get with a 250W double-ended in a ohp-design. Because the 150W bulb is much cheaper, here in Europe anyway, there is no point using a double ended bulb, but if you already have a double ended, keep using it.
250W 1-ended bulb, is availible here in Europe as MSD250 Philips and HSD250 Osram. But if you can find them in USA I don´t know.
Also, do you think you can get a manufacturers that makes the reflector with a 90 degrees angle, because that´s what we need if we don´t want to move the lamp backwards. The widest angle I have seen is 60 degrees, there must be a reason why they don´t make it wider.
Attachments
http://www.protheatrical.com/Scripts/prodList.asp?idCategory=70
They have both the phillips 250/2 and Osram 250 bulbs in stock for under $100 on a regular basis. Great lamp!
If you pay anything more for either of these lamps your getting ripped off.
They have both the phillips 250/2 and Osram 250 bulbs in stock for under $100 on a regular basis. Great lamp!
If you pay anything more for either of these lamps your getting ripped off.
mathias
I am building a projector with a 7 inchs LILIPUT.I am going to use a 150 watt cdm single ended lamp,i have cut two fresnels 4 inchs by 7 inchs and put them together between two pieces of glass to get six inchs focal lenght to the bulb.Does the beam coming out from the PAR 30 be enough to cover the back fresnel?
How do you remove the rear of the PAR30!
I am building a projector with a 7 inchs LILIPUT.I am going to use a 150 watt cdm single ended lamp,i have cut two fresnels 4 inchs by 7 inchs and put them together between two pieces of glass to get six inchs focal lenght to the bulb.Does the beam coming out from the PAR 30 be enough to cover the back fresnel?
How do you remove the rear of the PAR30!
jcbklyny and others,
I like the 250 watt single ended lamp even though it costs about $75. It has a higher color temperature and would probably be easier to use a reflector with. Do you happen to know what the diameter of this type of lamp are (they still look too wide to be used with a common PAR reflector)? Also, would anyone be interested seeing them available at DIY Labs for $65 if I can get them that cheap? I won't bother ordering them if people don't think it's worth the extra $$, but I'll be glad to help by offering them cheaper if there is interest in it. Please email me back at diylabs@hotmail.com or post something here if you think I should look into it. Thanks!
I like the 250 watt single ended lamp even though it costs about $75. It has a higher color temperature and would probably be easier to use a reflector with. Do you happen to know what the diameter of this type of lamp are (they still look too wide to be used with a common PAR reflector)? Also, would anyone be interested seeing them available at DIY Labs for $65 if I can get them that cheap? I won't bother ordering them if people don't think it's worth the extra $$, but I'll be glad to help by offering them cheaper if there is interest in it. Please email me back at diylabs@hotmail.com or post something here if you think I should look into it. Thanks!
phillips and osram have pdf specs sheets on their site. I have my own contact for ordering those lamps, so I wouldnt be interesting in buying somewhere else. They are both as small as the phillips 150 watt single ended as I have seen and used them both.
Those 2 lamps are used in almost ALL Intelligent stage lighting units made by high-end and martin lighting.
[edit: I attached one of the phillips 250/2 lamps I have on hand.
Those 2 lamps are used in almost ALL Intelligent stage lighting units made by high-end and martin lighting.
[edit: I attached one of the phillips 250/2 lamps I have on hand.
Attachments
That lamp look great. But i am still not convinced that only MH lamps can be used in the projector. I still like the halogene par idee. It is possible to calculate how mutch cooling (fan's) you need, I will search for the book and do the calculation. i will post the answer soon.
by the way: http://www.73.com/a/0069.shtml Is this something? Maybe voor DIYlabs? (They don't sell to individuals)
by the way: http://www.73.com/a/0069.shtml Is this something? Maybe voor DIYlabs? (They don't sell to individuals)
How to cut a PAR30 lamp.
Feel that I need to explane how to cut the PAR30 lamp without to crash it. The first thing you must have is an angle-cuter, with a disc to cut ceramics (picture 2), and the angle-cuter must have some adjustment for the speed, if it rotate too fast you will crack the lamp in wrong place.
1. Remove the metal base with a scissors and a small screwdriver.
2. Start to cut the back of the lamp at the place I show in the picture 3, if you cut it more backwards the HQI-bulb will not fit. Cut it thinner and thinner equal round the lamp, at the end it will break in the place you cut it, if it´s equal thin round the base. If you cut too much at only one side, it will break in the wrong place and a part of the reflector will get lost.
3. Remove the frontglass, this is the most difficult part, the frontglass is extremly hard, so you can´t just smash it. Use the angel-cuter and cut a stripe across the lamp (the green in picture 4) then cut a little at the edge a bit from the stripe, the front glass will break in small parts that you easy can bend away.
Use some sort of protection goggles, very sharp glasspieces can hit your eyes, normally there isn´t any glasspieces with this bulb but, but be carefull.
The hole in the middle is 21 mm wide, and the HQI-bulb is 20mm, so it can´t fit better.
Feel that I need to explane how to cut the PAR30 lamp without to crash it. The first thing you must have is an angle-cuter, with a disc to cut ceramics (picture 2), and the angle-cuter must have some adjustment for the speed, if it rotate too fast you will crack the lamp in wrong place.
1. Remove the metal base with a scissors and a small screwdriver.
2. Start to cut the back of the lamp at the place I show in the picture 3, if you cut it more backwards the HQI-bulb will not fit. Cut it thinner and thinner equal round the lamp, at the end it will break in the place you cut it, if it´s equal thin round the base. If you cut too much at only one side, it will break in the wrong place and a part of the reflector will get lost.
3. Remove the frontglass, this is the most difficult part, the frontglass is extremly hard, so you can´t just smash it. Use the angel-cuter and cut a stripe across the lamp (the green in picture 4) then cut a little at the edge a bit from the stripe, the front glass will break in small parts that you easy can bend away.
Use some sort of protection goggles, very sharp glasspieces can hit your eyes, normally there isn´t any glasspieces with this bulb but, but be carefull.
The hole in the middle is 21 mm wide, and the HQI-bulb is 20mm, so it can´t fit better.
Attachments
Cooling with fans, calculations
As promised.
Ok let me first say, that this is a aproximation. The real stuff is mutch more complicated.
So we want to calculate how much flow our fan has to give when we use for example a 1000 watt halogene. So lets start.
What we want to calculate is the volume air per second we are gona need to cool the lamp. So we rewrite the equation into this:
We can now fill it in:
Let say that we lose 90% of our halogene light as heat so
Q=0,9 kW. Cp and the density of air we know. Let say that we want the temperature inside to be max. 40 C and the outside temperature is 20 C. So the temperature difference is 20 degrees.
So the flow we need is ~0,05 m^3/s that is ~90 CFM (cubic feet per minute)
This would be correct if there was no resistant to the flow, but we al know that this is not true. The resistant causes a higher pressure which causes a lower flow. (see fig)
So if you want to be safe, you have to at least double the needed CFM.
So in this case 2x90=180 CFM
A normal 60mmx60mm fan http://www.coolerguys.com/ProductDetails.aspx?productID=485 only moves ~18 CFM.
A 80mmx80mm fan does ~39 CFM
And the best i found was a 120mmx120mm fan with 78 CFM.
"Oh no problem! I just install three of them!!"
This is not true, 3 fans does not mean automaticly 3x the flow.
This depents if you place them in serie (so side by side) or in a push and pull situation. But to now which system to use can only be measured and not predicted.
So a 1000 watt halogene can be cooled but you are taking a big risk.
For more information:
http://www.comairrotron.com/engineering/airflow.htm
The next graph shows the relation of CFM against kW halogene.
Remember. To be save double the CFM value.
Ps. This is just a calculation in real live other factors as conduction and raddiation also take place, so some spots in the projector can still get a lot hotter.
As promised.
Ok let me first say, that this is a aproximation. The real stuff is mutch more complicated.
So we want to calculate how much flow our fan has to give when we use for example a 1000 watt halogene. So lets start.
An externally hosted image should be here but it was not working when we last tested it.
What we want to calculate is the volume air per second we are gona need to cool the lamp. So we rewrite the equation into this:
An externally hosted image should be here but it was not working when we last tested it.
We can now fill it in:
Let say that we lose 90% of our halogene light as heat so
Q=0,9 kW. Cp and the density of air we know. Let say that we want the temperature inside to be max. 40 C and the outside temperature is 20 C. So the temperature difference is 20 degrees.
So the flow we need is ~0,05 m^3/s that is ~90 CFM (cubic feet per minute)
This would be correct if there was no resistant to the flow, but we al know that this is not true. The resistant causes a higher pressure which causes a lower flow. (see fig)
An externally hosted image should be here but it was not working when we last tested it.
So if you want to be safe, you have to at least double the needed CFM.
So in this case 2x90=180 CFM
A normal 60mmx60mm fan http://www.coolerguys.com/ProductDetails.aspx?productID=485 only moves ~18 CFM.
A 80mmx80mm fan does ~39 CFM
And the best i found was a 120mmx120mm fan with 78 CFM.
"Oh no problem! I just install three of them!!"
This is not true, 3 fans does not mean automaticly 3x the flow.
This depents if you place them in serie (so side by side) or in a push and pull situation. But to now which system to use can only be measured and not predicted.
So a 1000 watt halogene can be cooled but you are taking a big risk.
For more information:
http://www.comairrotron.com/engineering/airflow.htm
The next graph shows the relation of CFM against kW halogene.
Remember. To be save double the CFM value.
An externally hosted image should be here but it was not working when we last tested it.
Ps. This is just a calculation in real live other factors as conduction and raddiation also take place, so some spots in the projector can still get a lot hotter.
No reactions? I would realy love to hear if people measured the heat (temperature in the cabine), so if this makes any sence.
I hate myself at te moment, i went to a fleemarket last saturday and i bought an ballast for MH. The transformator, starter and condensator where nicely put in a metal box so i could't see how many watt it was. There where two types one with only the text 70VA and one with the text 250VA and i bought the 70VA one (for less than 5 dollar). After opening the metal box a read that 70VA is the same a 70W (P=UxI) :S. So I could have had a 250W ballast for 5 dollar and now i am stuck with a 70W one :S. Can i trow it away? or is 70W (55000 lumen) enough for a small projection (90" or so)? I now it will not be a bright projection with aprox 55 lumen output.
I hate myself at te moment, i went to a fleemarket last saturday and i bought an ballast for MH. The transformator, starter and condensator where nicely put in a metal box so i could't see how many watt it was. There where two types one with only the text 70VA and one with the text 250VA and i bought the 70VA one (for less than 5 dollar). After opening the metal box a read that 70VA is the same a 70W (P=UxI) :S. So I could have had a 250W ballast for 5 dollar and now i am stuck with a 70W one :S. Can i trow it away? or is 70W (55000 lumen) enough for a small projection (90" or so)? I now it will not be a bright projection with aprox 55 lumen output.
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