Leds

[Cory]

Im curious, if you buy an led chip rated at 660nm, does that mean it puts out only 660nm?

I made this in the chem forum because leds use phosphors or something which is a chemical

 

[Reefing Madness]

 

[Reefing Madness]

@Randy Holmes-Farley

 

[jason2459]

I would try and call upon @Luc Vogels

He helped to start the coral care LED system at Philips.

 

[Luc Vogels]

Hi Cory,
The simple answer --> yes you are correct

The detailed answer:
The present LED market knows two popular LED types.
They are commonly known as "direct LED's" and "Phosphor converted LED's".
A "direct LED's" is an LED that emits a narrow wavelength band and is specified on its "peak wavelength".
The most common direct LED is the Royal Blue LED with its peak wavelength somewhere between 445-460nm.

The spectral distribution of this LED looks as follows:

A phosphor converted LED uses a "basepump" (what is an direct LED), and with help of an Phosphorous layer (what can be on top of the LED, but also even remotely) this light can be transformed to a different spectrum.
In Example: The light of a direct Royal Blue LED can be transformed to a wide spectral color with an average colorpoint of 3000Kelvin (the lighttone that we typically use for our living room lighting).

The choice of phosphor and the thickness of this layer determines the colorpoint, color rendering and the efficiency of the light.

Picture Reference : http://www.lumileds.com/uploads/382/DS106-pdf

 

[jason2459]

Can these phosphors burn out sooner and shift the spectrum well before the base direct LED gives out? Is there a guesstimated general timeline on that?

 

[Luc Vogels]

Can these phosphors burn out sooner and shift the spectrum well before the base direct LED gives out? Is there a guesstimated general timeline on that?

Hi Jason, you are correct.

The phosphorus material degrades over time.
This depends on various factors... some examples:
The wavelength of the basepump --> The lower the basepump wavelength, the higher the energetic content per photon and the more destructive for the material.
The type of phosphor --> multiple phosphors are used to create white colors (e.g. the 3000K I referred to before). Each phosphor has its own properties and is more or less robust towards aging.
e.g. the phosphor that is used to generate the blueish wavelengths in fluorescent T5 lamps suffers from the mercury peaks (basepump) and degrades much faster compared to the other phosphors.
Therefor the color point of a T5 tube shifts over time (because the blue part of the spectrum is reduces (and slightly shifted). These blue wavelengths are very important for our Corals growth and this is the main reason you are advised to replace your T5 lamps every 6-12 months. You do not perceive a big drop in brightness, but for the coral the most useful wavelengths are reduced drastically.
The overall junction temperature of the LED and operation temperature of the phosphor --> Overdriving LED's or having poor cool will increase the degradation process.

It is hard to set a general timeline (due to the amount of variables). It can be from 10.000 hours (poorly designed) to 100k hours (industrial graded).

 

[new2mac]

I have 5 year old Radion. Let say it worked 365x10=3650 hrs annually. In 5 years LEDs will be close to 20K hr mark. Does it mean that I need a new light due to current LED degradation?

 

[Luc Vogels]

I have 5 year old Radion. Let say it worked 365x10=3650 hrs annually. In 5 years LEDs will be close to 20K hr mark. Does it mean that I need a new light due to current LED degradation?

The light output surely reduces during those 5 years of operation.
But the level of reduction is depending on the drive current and operation temperature of the LED.
(And secondarily also on material degradation of the optics).

It is also up to the consumer to decide when to exchange lighting...
Compare it with T5... some exchange every 6 months, others every 18 months.
Due to the many variables it is only verifiable by measuring the PAR values of the light during operation.

But it is good to assure the cooling of the fixture is optimal so you can enjoy the product lifetime as long as possible.

 

[new2mac]

Luc, thank you very much for sharing your thoughts on my question. Apparently there are many variables involved therefor no firm answer (which I hoped for).
PAR is relatively easy to monitor but I was rather concerned about some undesirable light spectrum shift due to LED degradation. Unfortunately there is no "hobby" way of testing that param and it remain up to reefer's subjective decision when to go for a new light.

 

[saltyfilmfolks]

Unfortunately there is no "hobby" way of testing that param and it remain up to reefer's subjective decision when to go for a new light.

spectrometer. https://www.google.com/search?q=spe...ectrometer,g_2:pocket,g_1:diffraction+grating
spectroscope
https://www.google.com/search?q=spe...hUKEwibvaGs543SAhXmqFQKHdzoBmMQ_AUIBygC&dpr=1

 

[new2mac]

@saltyfilmfolks spectrometers from your link look like pro lab equipment to me. With price tag starting at $2'000 I don't think even LFS would go for it not to mention ordinary hobbyist. That's what I meant.

 

[Luc Vogels]

Luc, thank you very much for sharing your thoughts on my question. Apparently there are many variables involved therefor no firm answer (which I hoped for).
PAR is relatively easy to monitor but I was rather concerned about some undesirable light spectrum shift due to LED degradation. Unfortunately there is no "hobby" way of testing that param and it remain up to reefer's subjective decision when to go for a new light.

Well... luckily also the price of a spectrometer is dropping (like it is doing for PAR meters).
But I agree they are still in the 1000$+ pricerange what is not very realistic number for just a verification measurement.
In Philips we sometimes use these handy Iphone click-on spectrometers. (http://www.lightingpassport.com/)
Relative cost competative and good performance!

Maybe you are engaged with a local aquarium group and you can buy one together>?

Subjective variables are indeed not desirable when you want to judge if your lighting is still ok...agree!
But don't forget that your animals will also warn you when the conditions become sub-optimal.

 

[saltyfilmfolks]

@saltyfilmfolks spectrometers from your link look like pro lab equipment to me. With price tag starting at $2'000 I don't think even LFS would go for it not to mention ordinary hobbyist. That's what I meant.

sorry, didn't get a notice on this,
its this one. https://www.teachersource.com/produ.../light-color?gclid=CMmfzbHhrtICFVCBfgodFcUKqw