# Multi fresnel lenses (fresnel-arrays)?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.

#### Tobias Claren

Hello.

Are there Fresnel lenses with many small Fresnel lenses? I know the parts of 3DLens,
An externally hosted image should be here but it was not working when we last tested it.

25x 3,5cmx3,5cm

but I look for smaller single lenses. Approx. 2cm to maximally 2,2cm.

Integrator lenses would be probably ideal.
Does someone have sources for such lenses (gladly in Germany)?

That would be to be analyzed a solution over with 166 (16x10) Toshiba "TL10W02-D"-LEDs a 15,4"-wuxga-tft.
That is 36 times more lights than from 2 the CCFL tubes.
"36" times the 15,4"-tft fits into the projection of 200x125cm.
Thus I need 36 times more lights.

,
Tobias

#### Guy Grotke

solution in search of a problem

That LED delivers 60 lumens/2 Watts = 30 lumens/Watt

MH lamps deliver 80 lumens/Watt

So LEDs will cost 2.6 times more to run, and will make much more waste heat.

To get the same number of lumens as a \$120 US 250 Watt MH lamp & ballast, you would need 333 of these LEDs. If you get them for the \$6.60 US sample price, then they would cost about \$2200 US. Of course, you would also need a power supply that could drive each chain of LEDs with a regulated 500 ma of current. You would also have to go to great lengths to keep them cool, because they probably only emit IR if they get too hot.

Everybody thinks LEDs are a cool light source, because they are used to dealing with 10 ma LEDs. 500 ma LEDs generate a lot of heat!

#### Tobias Claren

Re: solution in search of a problem

Guy Grotke said:
That LED delivers 60 lumens/2 Watts = 30 lumens/Watt

MH lamps deliver 80 lumens/Watt

So LEDs will cost 2.6 times more to run, and will make much more waste heat.

To get the same number of lumens as a \$120 US 250 Watt MH lamp & ballast, you would need 333 of these LEDs. If you get them for the \$6.60 US sample price, then they would cost about \$2200 US. Of course, you would also need a power supply that could drive each chain of LEDs with a regulated 500 ma of current. You would also have to go to great lengths to keep them cool, because they probably only emit IR if they get too hot.

Everybody thinks LEDs are a cool light source, because they are used to dealing with 10 ma LEDs. 500 ma LEDs generate a lot of heat!

I know !

This LED has 35 Lumens/Watt (3,4V x 0,5A). 1,7W.

"MH"? MHI?

Is the MHI not many more expensive than other burners?
Doesn't it "die" faster? What costs it per use hour?

The HQI etc. has around the 70 lumen Watts and 1A color.

More Heat? These LEDS can be operated without cooling. OK ONE, in large quantity I make air.
Yes, the LEDS have a worse efficiency.
But with the burner one needs a reflector, a condensor lens and a Fresnel with loss.
With the LEDS only many small lenses for straight light. Lenses can be made square.

Yes I need 333 of these LEDs, but I don't need a light-loss-reflector. The only loss would be the lenses before the LEDS.
There is round Spots, but square lenses. There still something light goes through inclined.
Still approx. 63% light remains on the lenses. he remainder falls on the surrounding lenses and withdraws diagonally.
The LED number should be divided by 63 and taken times 100. Thus one replaces the diagonally withdrawing light out.
Reflector losses with the burner and diagonal light with the LEDS could hold themselves possibly the balance. I don't know the loss-value of the burner-reflector.

\$6.60? This is the sample-Price. Starting from October 1 million per month (rising) in series are manufactured. Then they must be cheaper.
Yes, LEDS could (still) not better than (HQI etc..) its which concerns the current consumption.
If I use a back projection canvas, also during the day as much light is enough as at night.
That saves energy. That costs here \$0.2 per KW hour. If I with back projection with 150W-burner(or LED) get along would be good that. If necessary 250W.

#### renan

hello,

i saw some of this kind of fresnel on www.astromedia.de few month ago.

I'm not sure the size of each small fresnel will be small enough for you since I do not understand german .

just have a look

#### Guy Grotke

Metal Halide versus LED

>What costs it per use hour?

The Metal Halide lamp I am using is a Ushio 250 Watt retrofit: \$38 US for the lamp that has an average life of 15000 hours. That is about 1/4 of a cent US per hour.

>These LEDS can be operated without cooling.

If you look at the press release for this LED, they mention that this high power is only possible because they have improved the heat transfer to the mounting hardware. That mounting hardware will be attached to a heatsink, because you have to keep the LED junction below a certain critical temperature (100 C for 50% of rated light output with their other white LEDs). If you have many of these LEDs close together on the same heatsink, it will quickly get so hot that they stop generating visible light. You will need a very high flow of cooling air over the heatsink to keep them operating. The heatsink will have to be kept at a temperature lower than 100 C, so that heat will be transferred. You should be able to get the technical data from them to calculate the maximum heatsink temperature.

It is very easy to get heat transfer from a 350 C Metal Halide lamp to a 30 C air stream. It is much more difficult to get (even more) heat transfer from a 50 C heat sink to a 30 C air stream. You might need to use pumped water cooling with a large radiator, for 330 2 Watt LEDs.

If I were you, I would get a sample LED and mount it on a heatsink that is 1/330 of the area you plan to use for your LED array. Insulate all four sides. so it is a good model of the LEDs that are not at the edges of the array. Then see if you can keep it cool enough to operate for hours just by blowing air over the back surface. I think you will find you need to add huge aluminum fins to increase the effective surface area, to get enough heat transfer.

#### Tobias Claren

Do we mean the same lamps?: \$113 or 187,10 by 1000 hours lifetime

renan said:
hello,

i saw some of this kind of fresnel on www.astromedia.de few month ago.

I'm not sure the size of each small fresnel will be small enough for you since I do not understand german .

just have a look

No, this MFs are the same like 3Dlens. 3,5cmx3,5cm. Focus and extents must fit the LED. Hexagonal lenses would be better (the ligtspot are round). Those can make one from round lenses.
The Astromedie lenses are the same like 3DLens. 3,5x3,5. Too largely. Only 60 LEDS fit then behind the TFT. too little light.
My last estimations result in approx. ~350 pieces. That is very expensive with 600W (+ supply) in the maintenance. In Germany the KW hour costs at least \$0,20.

@Guy Grotke

Your data to the metal Halid lamp are very good. Here in the German forum there are "HMI"s. Those should have a good color reproduction and a littke more effective. But they "die" after 1000 hours and cost more (?).
Do we mean the same lamps?

"Ours" "Osram HMI 575 SE" cost approx. \$187.10 and/or the "Osram HMI 575 gs" for approx. \$113. Both hold only 1000 hours. That is too expensive me. The energy costs are already extreme. Both together results in a high hour price.

Those are per hour:
\$187-lamp: \$0,302/hour
\$113-lamp: \$0,228/hour
Very expensive in one year.

As TV replacement inclusive PC use in a 2-3-person-household could be the 16 hours on the day in enterprise (background). That costs then with the \$113-Lampe \$887.68 per year. With 25% absence \$665.76 per year remains. Too much.
Is there a smaller MH lamp? 250W?
Yes, many LEDS should be cooled. A draft of air should be enough. Alluminium radiators on the back would be also no problem (inclusive draft of air). In the back with radiator box and draft of air and in front only with draft of air.

#### Guy Grotke

OSRAM and USHIO

Some of those OSRAM lamps are very nice, with good color temperature and small arc lengths. But some of them are very expensive. The cost per hour for Metal Halide lamps has a very wide range!

I use a Ushio UHI-S250DD, which is a 250 Watt Metal Halide lamp designed to work with a High Pressure Sodium lamp ballast. It gives me 20000 lumens for 15000 hours, with a color temperature of 5200 K, and an arc length of 24 mm.

There is also a 400 Watt version: The UHI-S400DD. It gives you 33000 lumens for 20000 hours, with a color temperature of 5200 K, and an arc length of 27 mm.

Both of these lamps are available from atlantalightbulbs.com in the US for \$37.95. I think they are available in the EU for a comparable price, because Ushio has distributors all over the world.

You might want to check the prices at exclusiv-online. They have 250 Watt and 400 Watt OSRAM HQI-TS Daylight lamp sets that run for 12000 hours, and the replacement lamp cost is only 55 Euros.

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.