OT: Purple LED's ... UV ??? Yikes!....

[Melanhead]

Well upon having a discussion about 'em in the lounge ( they may be UV light and harmfull to eyes ... ) just wondering if anyone can shed some light as to the brand/specs that Smallbear sells as Steve is away for a few weeks ... I've been using 'em in pedals for on/off indictors.

here's the discussion from markr04

"I didn't think anyone actually used those as indicators. Those violet/purple LEDs are harmful and are not used as indicators for a very good reason. The big warnings on the datasheets for them are there to tell you: "Emits harmful UV radiation. Protect eyes and skin during operation."

I wouldn't be concerned about my skin from a single LED light. But we're supposed to look at indicator lights... with our sensitive little eyes. You don't want them to be "tanned".

The UV radation emitted from them is non-directional. It doesn't matter if you look at it directly or from a guitar-playing angle, it kills eyesight either way. Protect your and your friends' eyesight by not using them."

more in the thread ( data sheets etc ... )

here: http://diystompboxes.com/sboxforum/viewtopic.php?t=34372

any help would be appreciated ... the ones I have been using look more blue but they are listed as 5mm "Violet" ... and I bought 'em to be a bit different.

[MartyMart]

Hmm, I dont get that, its just a "violet" coloured LED, so whats the
difference from a "Ultra bright Blue" or a "green"  LED  ??
The colour "violet" has nothing to do with "UV" light from the sun .....

I dont think that's true, or steve would NOT sell them !!

Marty.

[Melanhead]

That's what I thought ... but these are water clear emitting a violet color ...

There are some Purple/Violet ones that are in fact UV ( after doing some reading in the other thread and research ... ) and some that aren't...

I'm assuming that one's I'm using are fine but wanna be on the safe side ... Steve sure did pick an odd time to go on vacation

[ethrbunny]

Might be a problem if you put your eye right up to it and stood there... but assuming you have it on the floor.. and its putting out 2v * .02A = .04W.. then you multiply by 1/R**2.. ... tap tap.. trying to remember..

(time goes by)

.. then when you realize that your physics classes were *way* too long ago to do this correctly..

I'd guess that under normal use its not going to be an issue. But, as always, I defer to the big brains around here.

[wampcat1]

I would guess that the amount of uv given is very minor -- I've been using them for several years now, and have never gotten so much as a slight tan!!  :roll:  :lol:

Seriously, I'd bet the warnings are there just to protect the company from lawsuits. I wouldn't be too worried about the uv factor, as long as you aren't sticking the led up to your eye.

</pure speculation>

[Vsat]

These UV LEDs  emit some visible violet light... but the main part of the emission spectrum is invisible ultraviolet radiation ... if your eyes could see ultraviolet directly they would look FAR brighter. Same with infrared (IR) LEDs.. you cannot see the infrared... but they are putting out a LOT of infrared (they are even more efficient than visible LEDs).

The UV LEDs are usually built to emit a fairly narrow focussed beam... you don't want to be staring directly into an efficient high-brightness red/green/blue/etc LED... why stare into the output of a UV LED?
Take care,
Mike

[spudulike]

Before people get panicky, any LED that emits light with a wavelength longer than 395nm are NOT uv leds.

True UV LEDs are around $40 a shot - check em out here The UV types you see on ebay/smallbear etc are UV as a descriptive name only. They are actually called "Near-UV". The shorter the wavelength the more damage they can do. As 99.99999% of consumer leds are above 395nm then the risk is minimal. Asa final caveat, any LED that can emit harmful light (ie 395nm and up) CAN do damage have to be supplied with the badge



You dont stare at the sun do you ?
Oh, and dont use laser diodes either

700-4900nm   Infrared
640-700nm   Red
625-640nm   Orange-Red
615-625nm   Orange
600-615nm   Amber
585-600nm   Yellow
555-575nm   Yellow-Green
515-540nm   True Green
490-510nm   Blue-Green
485nm      Sky Blue SiC
445-480nm   True Blue
430-440nm   Deep Blue
395-420nm   Violet
275-395nm   Ultraviolet

You might also want to check the LED Museum for more info.

[Melanhead]

Thanks for the info guys ... I'll e-mail Steve and get a data sheet or at least find out what brand/model they are.

[markr04]

True UV LEDs are around $40 a shot - check em out here The UV types you see on ebay/smallbear etc are UV as a descriptive name only. They are actually called "Near-UV". The shorter the wavelength the more damage they can do. As 99.99999% of consumer leds are above 395nm then the risk is minimal. Asa final caveat, any LED that can emit harmful light (ie 395nm and up) CAN do damage have to be supplied with the badge

$40? Mouser sells 380nm UV 5mm LEDs for $3.75 each (~$2 in bulk). I had a dozen true UV LEDs that were not marked as such when I bought them. They were $1.49 each. I don't think using cost as a differentiator is accurate.

I just read a post stating that the appearance of some 420nm LEDs (advertised as "violet") wasn't violet anyway, but a dark blue - which is what I remember that wavelength to be also. The links I posted to some datasheets in the OT forum do have a similar warning on them, like the "badge" you posted. That warning is on a 410nm LED also.

[formerMember1]

dumb question perhaps....

it looks like they call infared "infared" because it is the next higher to red.
likewise with ultra violet it goes violet then lower wavelength would be uv.
then how come the sun is uv but it is actually yellow.

[Jaicen_solo]

The sun is orange, because it's burning hydrogen. Simple as that.
The UV it emits cannot be seen with the naked eye so I guess that's why it doesn't look purple! No type of UV radiation can be seen, because we don't have the eyes for it. Don't worry about purple LED's, if you can see them, they're not efficient enough to be producing much UV.

[formerMember1]

it was a dumb question but it was worth finding an answer too
thanks..

[Vsat]

Try this for an experiment if you have an oscilloscope handy (or a spoonful of laundry detergent powder):

Turn off the lights, shine the beam from a "UV" LED on the o-scope screen (or detergent powder) from six feet away and the screen will light up bright green ... and phosphoresce for several seconds after the UV is turned off. The powder will fluoresce bright blue-white. Works MUCH better with a UV LED than with a blue LED, even though the purple light is not particularly bright compared to a blue or green  or red or white LED. Most of the glow on the o-scope screen is caused by the invisible portion of the UV LED emission spectrum, rather than the visible purple emission.
Cheers, Mike

[markr04]

Don't worry about purple LED's, if you can see them, they're not efficient enough to be producing much UV.

I humbly disagree. We can see the sun (as orange, 615nm at that), yet we know it emits enormous amounts of UV (and intrared, and radio, and...). We can see tanning bed lights too. My point is that just because something is emitting UV, does not mean its limited to such a narrow wavelength (invisible) band. The sun emits a very, very wide band of energy. In the case of the purple 380nm UV LEDs, they're emitting both UV wavelengths and visible wavelengths.

I never intended to create such a hot topic by pointing out the UV-capabilities of the purple LEDs in the OT forum. Apparently, the ones coming from Small Bear are actually blue, not really violet - which I didn't know when I responded to the post. The datasheet for those LEDs shows that the peak wavelength is 420nm, which is safe. This shouldn't be of any concern here, but what we don't know about any of these LEDs is how wide the curve is (how far above and below that freq it emits). For an LED operating with a peak of 420nm, I wouldn't be concerned about it. I would be if that was a larger lamp hanging over my solder table .

Just look at your datasheets. If the LED's peak is in the UV range, it will have a warning on the datasheet - like the ones I posted in the OT forum.

It appears we all learned a little bit about the myths and facts of UV "light". Now back to effects projects...

[formerMember1]

:D

[markr04]

That's considered "hijacking a thread" - off-topic postings that stem from the original topic.

There's an active thread in this forum that deals with battery drain and LEDs. "3mm vs. 5mm LED battery drain?"
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=34499

In the future, search the forum for answers to your questions first (search button at the top of the site pages). It's likely your question was already asked and answered by other members. If no answers, post your question under a new topic. In this case, join in under that thread I mentioned above. This timing couldn't be more coincidental.

[formerMember1]

oh thanks... i just became a member of this forum within a week or so and very few posts. thanks again

[markr04]

oh thanks... i just became a member of this forum within a week or so and very few posts. thanks again

I should've said this first: Welcome to the forum!

There is more knowledge between the members here than you will most likely ever need. Unfortunately, I'm not one of the knowledgeable folks on circuits. But I try to soak in as much as possible as my expertise isn't electricity. :oops:

I hope I didn't come across as "scolding" you.

[formerMember1]

no harm done.  i apprecitate the info.  i am new to the computer world beleive it or not.  especially using the internet(& forums).  thanks again...