Effect of direct sunlight on an LED?

I have been playing around with my H501w in the evening sunlight, and noticed that when it was on low and I exposed the led directly to the sun it flickered and if done face on actually went out completely.

I had thought that it was just an optical illusion, as the sunlight could be drowning out the low level light emitted. However, having inspected it a bit closer the sunlight is actually extinguishing the led completely.. It turns on again as normal afterwards, but every time that I do it it turns off when exposed to the sunlight. :thinking:

My questions are; why does this happen, and could it have any long term effects on the led?

RedForest UK said:

I have been playing around with my H501w in the evening sunlight, and noticed that when it was on low and I exposed the led directly to the sun it flickered and if done face on actually went out completely.

I had thought that it was just an optical illusion, as the sunlight could be drowning out the low level light emitted. However, having inspected it a bit closer the sunlight is actually extinguishing the led completely.. It turns on again as normal afterwards, but every time that I do it it turns off when exposed to the sunlight. :thinking:

My questions are; why does this happen, and could it have any long term effects on the led?

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Its over heating, The lens is sending the sun light back to the led.

I tried the same thing with all my flashlights and none flickered...

and I got a pretty strong sunlight here

RedForest UK said:

I have been playing around with my H501w in the evening sunlight, and noticed that when it was on low and I exposed the led directly to the sun it flickered and if done face on actually went out completely.

I had thought that it was just an optical illusion, as the sunlight could be drowning out the low level light emitted. However, having inspected it a bit closer the sunlight is actually extinguishing the led completely.. It turns on again as normal afterwards, but every time that I do it it turns off when exposed to the sunlight. :thinking:

My questions are; why does this happen, and could it have any long term effects on the led?

Click to expand...

For what it's worth, that shouldn't happen. Check the contacts in the light and make sure the connections are tight. If anything, the UV in sunlight should slightly activate the phosphor. Cree uses UV-resistant stuff in their domes. The wires and phosphor don't care. Normally UV damage happens over months.

That sounds extremely odd. So you turn the light on, expose it to the sun, led goes out, turn the led away from the sun, and it is still 'out'? At what point does it come back on, after you turn it off and back on?

Can you post a video of the issue?

I don't understand the part of your post where you say "done face" but the rest intrigued me. Hooked a Cree XP-G up to my DVOM and it definitely outputs when I shine my Novatac K2 on it with the High setting.

V DC setting. When it's in the mV setting I have to put my hand over it to eliminate V out. With ambient light I get a reading of .155V, with the Nova right on it it reads 2.24V DC.

uA setting. Idle it's pretty close to 00.1, with the Nova it jumps up to 18uA.

People often think of electrical components and devices as operating in a one-way fashion. However, a speaker can act as a microphone, a starter can also pull duty as a generator, etc..

The test was performed with no bias on my part, the equipment is well maintained and I have tested it against know values, and the results were instantaneous and required no coaxing, 0 in the dark, higher values when I shined the light on it. I'm sure a CPF Google search will pull up something but I didn't think about that until after my test.

Anyway, this is all leading to me speculating that it may be feeding back in to the circuit causing it to shut down.
Or the heat from direct sunlight could cause some component to expand enough to create an open circuit.
Or there is a fleck of solder in the circuit that leans up against an IC when you angle it up towards the sun.
Or you've got a bad battery.

was.lost.but.now.found said:

That sounds extremely odd. So you turn the light on, expose it to the sun, led goes out, turn the led away from the sun, and it is still 'out'? At what point does it come back on, after you turn it off and back on?

Can you post a video of the issue?

Click to expand...

Yes, that is exactly it. It only happens on low mode, the led flickers when exposed to strong sunlight at an angle, and if directly in front of it it turns off completely, and is still off when turned away from the sun. However it comes back on as normal when switched on again, the sunlight basically acts like turning the light off.

I'm not sure about doing a video tbh, I have no real means of doing that. It works exactly as you describe though. I have tried it again a minute ago, but as the sun is almost down now it doesnt seem to have the same effect.. :thinking:

Hmm.. I really hope this isnt a serious problem, I just thought it was an interesting but slightly worrying observation.

I just took two lights, including my (reflectored) Zebralight SC30 outside into strong direct sunlight, while on minimum power no less. No effect whatsoever. Sorry I'm clueless to the issue.

bansuri said:

I don't understand the part of your post where you say "done face" but the rest intrigued me. Hooked a Cree XP-G up to my DVOM and it definitely outputs when I shine my Novatac K2 on it with the High setting.

V DC setting. When it's in the mV setting I have to put my hand over it to eliminate V out. With ambient light I get a reading of .155V, with the Nova right on it it reads 2.24V DC.

uA setting. Idle it's pretty close to 00.1, with the Nova it jumps up to 18uA.

People often think of electrical components and devices as operating in a one-way fashion. However, a speaker can act as a microphone, a starter can also pull duty as a generator, etc..

The test was performed with no bias on my part, the equipment is well maintained and I have tested it against know values, and the results were instantaneous and required no coaxing, 0 in the dark, higher values when I shined the light on it. I'm sure a CPF Google search will pull up something but I didn't think about that until after my test.

Anyway, this is all leading to me speculating that it may be feeding back in to the circuit causing it to shut down.
Or the heat from direct sunlight could cause some component to expand enough to create an open circuit.
Or there is a fleck of solder in the circuit that leans up against an IC when you angle it up towards the sun.
Or you've got a bad battery.

Click to expand...

Sorry, the 'done face' bit was meant to mean; if the same test was done with the light facing the sunlight directly. But I worded it a bit weirdly.

I'm not too sure I understand your test exactly, but then I'm no electronics expert. When you say that it 'outputs' do you mean it switches off or continues putting out light?

I gave it a very brief technical consideration with my limited knowledge and thought maybe the sunlight was acting reverse ways in the circuit by saturating the phosphor/light emitting part of the led, causing it to shut down, but I wasnt really sure if that was at all plausible so I put it up to the knowledge of cpf!

I am certain however that it is not to do with the orientation of the light in general or a bad battery, I have been using this light and this cell for a good few weeks now and have never experienced a similar problem.

Thanks for the input everyone anyway.

I hooked a bare LED up to a digital volt/ohm meter and shined a flashlight at it, the LED produced voltage and current.
My idea was that this small voltage is feeding back into the light engine and shutting it off.
I have a 501 and will test it both inside and out and report back.

RedForest UK said:

Sorry, the 'done face' bit was meant to mean; if the same test was done with the light facing the sunlight directly. But I worded it a bit weirdly.

I'm not too sure I understand your test exactly, but then I'm no electronics expert. When you say that it 'outputs' do you mean it switches off or continues putting out light?

I gave it a very brief technical consideration with my limited knowledge and thought maybe the sunlight was acting reverse ways in the circuit by saturating the phosphor/light emitting part of the led, causing it to shut down, but I wasnt really sure if that was at all plausible so I put it up to the knowledge of cpf!

I am certain however that it is not to do with the orientation of the light in general or a bad battery, I have been using this light and this cell for a good few weeks now and have never experienced a similar problem.

Thanks for the input everyone anyway.

Click to expand...

This is perfectly normal as it is an issue with majority of the dies. Mostly the larger ones with more real estate.

Think of it this way:

When you have photons that are being emitted by the light, the light of course is going to be washed out by the sun. This in effect will cause the potential of the photons being emitted to somewhat studder as they come out and when there is direct sunlight it would turn it off.

You can think of photons as small water source and the sun as a much larger water source. One of them has a much larger potential and will cause some turbulence when one is trying to fight pressure from the other. Air, water and electricity have the same basic physics. For example a capacitor is a perfect example of a water tower on a hill, etc...

Then as pointed above there are probably some led phosphors that have a uv resistant makeup but the sun will still win. Think of a magnifying glass that is taking a 1000W/m^2 and shooting it into the die and if the led survives, I would think that some sort of quirky effects would happen.

Don't worry this is perfectly normal. Also if there is a diode, this would only allow one path of current so this will not effect the electronics or batteries. Its just reacting the way it should. An led will act like a photovoltaic panel and will pull in power when exposed to light but has the benifit of emitting light too, it just has a poor efficiency when running backwards(as a P.V. panel). It might be causing some damage but everything has an exponential decay...

Hope this helps

Oh, and I have just tested it again by shining a few of my other lights on it while it is on low mode.

The results are that none of my lights have any effect on any mode.. Apart from my Nailbender 1.4A 5000k XP-G drop-in which also completely turns the light off when shone directly onto it in low mode. That adds something interesting I think.. Time for another :thinking:

My 501 does the same thing as yours!
Cool find RedForest!

ama230 said:

This is perfectly normal as it is an issue with majority of the dies. Mostly the larger ones with more real estate.

Think of it this way:

When you have photons that are being emitted by the light, the light of course is going to be washed out by the sun. This in effect will cause the potential of the photons being emitted to somewhat studder as they come out and when there is direct sunlight it would turn it off.

You can think of photons as small water source and the sun as a much larger water source. One of them has a much larger potential and will cause some turbulence when one is trying to fight pressure from the other. Air, water and electricity have the same basic physics. For example a capacitor is a perfect example of a water tower on a hill, etc...

Then as pointed above there are probably some led phosphors that have a uv resistant makeup but the sun will still win. Think of a magnifying glass that is taking a 1000W/m and shooting it into the die and if the led survives, I would think that some sort of quirky effects would happen.

Don't worry this is perfectly normal. Also if there is a diode, this would only allow one path of current so this will not effect the electronics or batteries. Its just reacting the way it should. An led will act like a photovoltaic panel and will pull in power when exposed to light but has the benifit of emitting light too, it just has a poor efficiency when running backwards(as a P.V. panel). It might be causing some damage but everything has an exponential decay...

Hope this helps

Click to expand...

Thanks, that really helped explain it and sort of confirmed what I had a very rough feeling might be going on.

So, all in all, this is normal as when the light coming out of the led is significantly less than the light going in the circuit is reversed and so the led shuts off, a bit like a very one sided scrum in Rugby?

The main question then is how much damage this could cause? Would you say it was just like running the led at a high output and taking a couple of hours of the 50,000hr lifespan. Or is it more serious and should I try to protect it from direct sun exposure? :shrug:

Thanks

bansuri said:

My 501 does the same thing as yours!
Cool find RedForest!

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Ha ha, I think thats good! At least I'm definately not the only one! Hopefully it doesnt damage the led at all, thats the conclusion I'm waiting for someone who knows their photovoltaic led stuff to tell us..

I recall reading something about this.


Was here on CPF (of course), perhaps a couple years ago.


Very interesting.


_

RedForest UK said:

Ha ha, I think thats good! At least I'm definately not the only one! Hopefully it doesnt damage the led at all, thats the conclusion I'm waiting for someone who knows their photovoltaic led stuff to tell us..

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Not to worry. No damage will occur. For a time I thought I had a bunch of defective drivers as I would test my lights outside during the daytime and half of them wouldn't turn on. I'd stick the light out the door of my shop and nothing. Then as I swing the light back into the shop it would turn on. Took me a while to realize the light was shining on the die and reversing the charge which canceled out the voltage coming in to the switching pin. I had the biggest laugh the day it all finally came together.

bansuri said:

I hooked a bare LED up to a digital volt/ohm meter and shined a flashlight at it, the LED produced voltage and current.
My idea was that this small voltage is feeding back into the light engine and shutting it off.
I have a 501 and will test it both inside and out and report back.

Click to expand...

Thanks for clarifying, I understand now having re-read your first post. Those results do seem quite conclusive about the led acting both ways. I wonder if it would be possible to work out a backwards efficiency rating, I'm guessing it would be way too low to be of any real practical worth?

saabluster said:

Not to worry. No damage will occur. For a time I thought I had a bunch of defective drivers as I would test my lights outside during the daytime and half of them wouldn't turn on. I'd stick the light out the door of my shop and nothing. Then as I swing the light back into the shop it would turn on. Took me a while to realize the light was shining on the die and reversing the charge which canceled out the voltage coming in to the switching pin. I had the biggest laugh the day it all finally came together.

Click to expand...

Okay thanks, I will accept you as 'someone who knows their stuff about photovoltaic led stuff' and feel better now.

That wasnt meant to be ironic btw, I've been admiring your DEFT for quite a long time now, even before I joined cpf. Hopefully by the time I've finished uni and have a full time job you might have something even more impressive in the works! :thumbsup:

I would have to say though that when youre getting your biggest laughs from solving a problem about reverse charging cancelling out input voltage in a switching pin on an led board, that may be a sign of being a little too shall we say 'involved' in the hobby! But then again, I think most of us here are in a similar boat, and if it leads to more world leading developments like DEFT, then I for one am not complaining!

RedForest UK said:

I wonder if it would be possible to work out a backwards efficiency rating, I'm guessing it would be way too low to be of any real practical worth?

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Interesting thought! Even if not you've got a good mind for looking at things from different angles.

Noteworthy: I get nothing(~) out of 2 different Cree XR-E R2(large die) emitters, only from the XP-Gs(small die) (tested 3 different XP-G, similar results) so add that to the equation.