88 watt Leds
- Thread starter luisagos
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I'm with evilc66 on the optics issue...... I see a problem with the data analysis. According to the data sheet the viewing angle is 140 Degrees. The viewing angle is the off axis angle from lamp centerline where the luminous intensity is 1/2 peak value. The total included angle is 160 degrees. The total included angle is the total angle at which 90% of total luminous flux is captured. So what this says basically is all the light output of the LED can be captured in a total angle of 160 Degrees. So when you look at the radiation patterns on page 20 of the data sheet you see at 45 Degrees you have an intensity of about 70%. That means you are losing 30% of useable light that can be focused down into your tank. I'm not sure if you realize that when you read 45 Degrees it's not the total angle it's 45 x 2 = 90 Degrees. So what optics will do for you is collimate all that usable light and focus it into a nice beam pattern of say 40 total Degrees. So that being said I find this thread puzzling.... The picture of the 48" lighted tank does not make sense from my experience with LEDs.
I would like to see some PAR readings.
I would like to see some PAR readings.
I use a microprocessor to control dimming, timer, etc... I could easily incorporate a serial com port to interface a PC. I considered this at the start but rejected it. The settings (sunset, sunrise, intensity,etc.)are programmed at installation held in RAM and not really changed after that. I'm not sure what the AI controller PC interface does...... anybody?
WOW guys !
First of all, i would like to give thanks to all here, I have learned a lot about LEDs and that I also need to learn some more about them.
I wanted to post something earlier, but it was a rough day at work.
Now being at home, and had my Dinner, i can enjoy this thread again.
I understand about the viewing angle loss of these LEDs. So I do agree with both of you on that note.
But I am also going to disagree about the loss. Remember we are not just using just one LED, we using over 36 star LEDs.
Like lynxvs said, at around 45 Degrees we are at 70% of what the LED is producing. The rest of the 25% is still being use, but at a different way. I see 5 % of the led power as wasted light, but not so completely either.
Keep in mind, my tank is 72" long, 18" deep and 22" high. Some of those LEDS are going to hit something in my tank, within the 3D world I created. Very important to say this again, we comparing 36 star LEDs in 3D surface.
Led lights do not pollute the tank with light, we must focus them in pattern that they can intercept each other.
By looking at these LEDs, they seem to do that well. Just looking at the tank pics, you can see what is happening. Look at the sides of the tank, there is where your going to see the the loss of the LEDs power, because they don't intercept anymore.
I like the idea, that I am going to get bad par numbers around the sides of my tank, can you say no algae growing there.
You can always fix that with low power lights place at the corners, to remove any shadows.
Well anyways, that what i think, and i could be 100% wrong, lol.
But the cool thing, I am learning and I would hope, all those following this thread are also enjoying this, even if they are silent. We have over 400 click on this thread, so it seem there is some interest for it.
First of all, i would like to give thanks to all here, I have learned a lot about LEDs and that I also need to learn some more about them.
I wanted to post something earlier, but it was a rough day at work.
Now being at home, and had my Dinner, i can enjoy this thread again.
I understand about the viewing angle loss of these LEDs. So I do agree with both of you on that note.
But I am also going to disagree about the loss. Remember we are not just using just one LED, we using over 36 star LEDs.
Like lynxvs said, at around 45 Degrees we are at 70% of what the LED is producing. The rest of the 25% is still being use, but at a different way. I see 5 % of the led power as wasted light, but not so completely either.
Keep in mind, my tank is 72" long, 18" deep and 22" high. Some of those LEDS are going to hit something in my tank, within the 3D world I created. Very important to say this again, we comparing 36 star LEDs in 3D surface.
Led lights do not pollute the tank with light, we must focus them in pattern that they can intercept each other.
By looking at these LEDs, they seem to do that well. Just looking at the tank pics, you can see what is happening. Look at the sides of the tank, there is where your going to see the the loss of the LEDs power, because they don't intercept anymore.
I like the idea, that I am going to get bad par numbers around the sides of my tank, can you say no algae growing there.
You can always fix that with low power lights place at the corners, to remove any shadows.
Well anyways, that what i think, and i could be 100% wrong, lol.
But the cool thing, I am learning and I would hope, all those following this thread are also enjoying this, even if they are silent. We have over 400 click on this thread, so it seem there is some interest for it.
Thing is though, you can't get high PAR at the bottom of a 24" deep tank without optics. Just doesn't happen, no matter how many LEDs you have over the tank. The quantity of LEDs is used for coverage. Optics are used to increase intensity and penetration.
Think of optics as different stages of MH power levels. No optics would equal ~70W, 60 degree optics would be equal to ~150W, and 40 degree would be equal to ~250W (these are actual tests that I have done). These all relate to single emiter arrays, not triples.
Think of optics as different stages of MH power levels. No optics would equal ~70W, 60 degree optics would be equal to ~150W, and 40 degree would be equal to ~250W (these are actual tests that I have done). These all relate to single emiter arrays, not triples.
sonnus
Member
evilc66, your forgetting to account for the refraction of the light as it enters the water. The closer it is to the surface of the water the better. So even if the LED has a 140 deg native beam once the light enters the aquarium it is bent into a tighter beam, improving penetration. You can calculate this with Snell's law.
Your comparison of different collimators or lenses only applies if you were using the light in open air without the water in the aquarium.
An interesting experiment to illustrate this is to shine a flashlight into your aquarium at an extreme angle (almost parallel to the surface). You will notice the light is bent once it enters the water, somewhere around a maximum of 49 deg (according to Snell's law). This is what you are seeing in smgsllc's photo.
sonnus
You bring up an interesting point that I didn't think of.... athough I don't think it makes that much difference in the final result. Say the LED viewing angle is 140 Deg. using Snells law the angle normal to the surface would be 90 - 140/2 = 20 Deg. Calculating the second angle using Snells law you end up with 15 Deg. So you really only gained a 5 Deg. beamwidth improvement. That means you have 140 Deg. hitting the water and 130 Deg. past the water interface not nearlly enough to get the results that I see in that tank..... I would like to see a photo of the light positioned over the tank.....I don't see it in the photo.
sonnus
Member
Using Snell's law:
If a beam of light transistions from air to water at an angle of incidence of approx 78 deg it will have an angle of refraction of approx 47 deg. This means ALL of the light coming out of a 140 deg LED (70 deg halfangle) will enter the water (essentially no reflected light) and have a halfangle of no more than 45 deg as long as the LED is close enough to the surface of the water (a couple of inches). The aquarium water IS the lense in this case. Plus, you don't loose 8-10 % of the light from the inefficiency of the collimator/reflector.
Depending on what you are trying to accomplish a collimator may be better but without a collimator you still have decent penetration because of refraction.
To compare:
No collimator with 130 deg LED beam = 90 deg refracted beam
50 deg collimator (25 deg halfangle) = 70 deg refracted beam
40 deg collimator (20 deg halfangle) = 54 deg refracted beam
The critical angle for the aquarium water is around 78 deg. Light rays have to be above this angle (156 deg LED beam) to be reflected.
If a beam of light transistions from air to water at an angle of incidence of approx 78 deg it will have an angle of refraction of approx 47 deg. This means ALL of the light coming out of a 140 deg LED (70 deg halfangle) will enter the water (essentially no reflected light) and have a halfangle of no more than 45 deg as long as the LED is close enough to the surface of the water (a couple of inches). The aquarium water IS the lense in this case. Plus, you don't loose 8-10 % of the light from the inefficiency of the collimator/reflector.
Depending on what you are trying to accomplish a collimator may be better but without a collimator you still have decent penetration because of refraction.
To compare:
No collimator with 130 deg LED beam = 90 deg refracted beam
50 deg collimator (25 deg halfangle) = 70 deg refracted beam
40 deg collimator (20 deg halfangle) = 54 deg refracted beam
The critical angle for the aquarium water is around 78 deg. Light rays have to be above this angle (156 deg LED beam) to be reflected.
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Sonnus, all of my tests are done in water. Why would I test out of water when there is a noticable difference in PAR from open air to water. I'm not just making this stuff up. I have done a lot of testing on verious setups over the last few years.
I may not use equations to estimate my results, but I do use real world tests, with real world results.
I may not use equations to estimate my results, but I do use real world tests, with real world results.
sonnus
Member
evilc66, I am not questioning your experiments, I am just supporting this light manufacturer's comments. He stated that the beam was approx 45 deg in the water and Snell's law proves that this is true.
If his light (smgsllc's) is close enough to the water his 140 deg LED beam will be transmitted completely into the aquarium and refracted to a 90 deg beam. Not much different from the 70 deg refracted beam that the 50 deg collimator will produce (and we don't loose 10 % of the light to the collimator).
I have done experiments with light also (including LEDs) and using Snell's law is very helpful and extremely accurate.
BTW, if it were my light I would probably use collimators so I could keep the fixture further off the surface of the water, not neccesarily to improve penetration.
If his light (smgsllc's) is close enough to the water his 140 deg LED beam will be transmitted completely into the aquarium and refracted to a 90 deg beam. Not much different from the 70 deg refracted beam that the 50 deg collimator will produce (and we don't loose 10 % of the light to the collimator).
I have done experiments with light also (including LEDs) and using Snell's law is very helpful and extremely accurate.
BTW, if it were my light I would probably use collimators so I could keep the fixture further off the surface of the water, not neccesarily to improve penetration.
I agree with the 90 deg. result I made an error in my original calculations. Since the light is so spread out at a 90 deg beamwidth what happens at the sides on the aquarium? does the light then refract back out of the tank? I still do not see how you got a 70 deg. refracted beam from a 50 deg collimator I get 37 deg refraction from a 50 deg. lens and 30 deg from a 40 deg lens.
sonnus
Member
I double checked my calcs are they actually wrong because I was using the halfangle. You are right with the 37 deg beam refracted beam for the 50 deg colllimator.
On the wider beam the glass actually reflects most of the light back into the aquarium. If you have a laser pointer to shine into your aquarium the reflected and refracted light at different angles of incidence are very easy to demonstrate.
On the wider beam the glass actually reflects most of the light back into the aquarium. If you have a laser pointer to shine into your aquarium the reflected and refracted light at different angles of incidence are very easy to demonstrate.
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