HELP I'm new WHY does this work?

[nukeiridium]

HELP I\'m new WHY does this work?

Hi everyone, I'm new to using LED's in general. What I did is purchased 6 of the following UV LED's:

http://www.superbrightleds.com/leds/uv_specs.htm

I then took a Mag Lite that uses 6 D cell batteries, took an extra bulb, broke it, and soldered the 6 LED's in a pattern like this on the end of the bulb: (view from looking into face of flashlight)

[image]http://cleedo.com/leds.bmp[/image]

Then I put it all together. It shines really bright UV light and I tried using it for scorpion hunting. It works great so far and I can see scorpions glowing green from like 15 feet away.

Now, my question is, shouldn't this burn the LED's out? I'm running them at 4.5 volts when their max is supposed to be 4 volts. I have no idea what Ma the batteries are because the damn things don't say anywhere on them. They are fresh batteries. So far I have used the light for approximately 4 hours straight without any noticeable change in brightness or color.

Why does this work? Is it just going the make the LED's not last very long? I took the lens off while the light was still on and had been in use for 30 minutes or so and the LED's were not warm.

Please tell me what you think. Sorry about my ignorance in this area, I'm just curious about this particular project.

 

[LEDmodMan]

Re: HELP I\'m new WHY does this work?

/ubbthreads/images/graemlins/yellowlaugh.gif newbie... /ubbthreads/images/graemlins/wink.gif

The way I understand you, the LEDs are all wired in a series/parallel configuration so they each see 4.5v?

If so, welcome to the world of overdrive!!!

If not, then how are they wired?

Eventually, the LEDs will dim and stop working. Actually, the epoxy dome will probably turn yellow first.

 

[nukeiridium]

Re: HELP I\'m new WHY does this work?

All 6 are wired in parallel. How long before the LED's should start degrading? I've run it for at least 5 hours now and no difference I can see. This light will only be used for scorpion hunting and possibly for shining on girls at parties (can you guess why? LOL) /ubbthreads/images/graemlins/smile.gif So I won't be using it super often. It doesn't need to last for eons.

 

[LEDmodMan]

Re: HELP I\'m new WHY does this work?

OK, if all 6 are wired in parallel, each one should be getting 9v if you're using a 6D maglight. So how are you running them at 4.5v? If they are each getting 9v, don't expect it to last too long. If you're only running it at 4.5v then the LEDs should last nearly their full lifespan.

PS - DON'T shine this light at anyone!!! The UV from the LEDs is VERY bad for the eyes!!! It can cause cataracts among many other eye problems. KEEP THE UV OUT OF THE EYES!!!

 

[LEDmodMan]

Re: HELP I\'m new WHY does this work?

FYI: You should either have this post or the other one locked. Cross-posting is not allowed and can get you banned. Contact an admin. or mod.

 

[The_LED_Museum]

Re: HELP I\'m new WHY does this work?

I locked the other thread and left "bread crumbs" behind so viewers will be able to find this thread. /ubbthreads/images/graemlins/grin.gif

 

[tvodrd]

Re: HELP I\'m new WHY does this work?

nukeiridium,

First, welcome to the forums! I too am an avid scorpion murderer- I mean hunter. /ubbthreads/images/graemlins/grin.gif (Prefered round: .22 Mag birdshot.) I started with 6" fluorescent, progressing to twin 2" CCFL, followed by a 30mA/diode converted Innova to an "I can't talk about it, that I haven't tried yet." My best-to-date is only good to 6-8Ft. Sounds like you have created a great tool! Remember, If it dies, they come in force and it's your turn. /ubbthreads/images/graemlins/grin.gif (I hate scorpions!)

Larry

 

[Steelwolf]

Re: HELP I\'m new WHY does this work?

Hmmm... good question. Why does it work? You have put all the LEDs in parallel in to a 6 D Mag. 6 cells means 9V if the cells are all relatively fresh. D-size cells means it should have no problem giving up to 1A of current.

UV LEDs, of course, have a slightly higher Vf because of the nature of the quantum energy jump required to produce light in solid state devices, though they are nominally rated at 3.6V. So they should work better with slightly higher voltages.

But 5mm LEDs have that epoxy casing around it, which makes it difficult to dispose of heat generated. The only pathway is through those thin leads. That's why it is so hard to overdrive 5mm LEDs without killing them, or severely shortening their life.

I think what is happening in your mod is that the LEDs are right at the edge of blowing up. You can't feel the heat because the epoxy casing is insulating most of that, and whatever heat manages to leave via the leads (which isn't much) is being effectively sinked by the PR bulb base.

The brightness doesn't change by much over 5hrs partly because you are using D cells on only 6 LEDs (nominal 240mA current draw) which wouldn't drain the cells much. Partly, the amount of light decreases only ever so slightly over that 5hrs period that your eyes can adapt. And partly, you started out with 9V, it will be a while before you reach the Vf of the LEDs, which is when you will see dramatic dimming.

And I'll echo LEDmodMan's warning not to shine the light at anyone. Regular LEDs are quite blinding as it is, UV will do even more damage.

As for your secondary usage to illuminate girls at parties, I assume it has something to do with the wavelength of UV and its penetration of the flimsy pieces of cloth which are their poor excuse for clothing? /ubbthreads/images/graemlins/smile.gif LOL Just off topic, those "clothes" they wear!!! Might as well save the bother and go naked.

 

[radellaf]

Re: HELP I\'m new WHY does this work?

I was thinking more Lewinski's dress type "forensics" on the gals. Good luck, it ain't THAT fluorescent.

Beats me why those LEDs haven't popped yet.

Know what you mean about the "clothes." All of a sudden everyone's joined the Navel Academy.

 

[nukeiridium]

Re: HELP I\'m new WHY does this work?

Oh jeez, dangit! I just realized I typed 6 D in my message, I mean to say 3 D! Ugg... That was a major typo... Anyways it is a 3 D flashlight so the LED's are all getting 4.5 volts.

So, knowing this, what do you think about the lifespan of the LED's? Do you think they'll last a while or burn up soon?

I used it again tonight for about an hour and still no change.

As for the clothes I was just joking about how sometimes if you shine a blacklight on a girl who is wearing a white bra, the bra will light up and shine through her shirt 😛 At least it has happened with other blacklights, we'll see if it works with this one....

 

[Steelwolf]

Re: HELP I\'m new WHY does this work?

Ahhh... 3 D cells. Well, no mystery there. The Trek 7 that I had used 3 C cells with no resistor. It was supposed to give 14hrs or thereabouts before noticeable dimming, hundreds of hours before it died.

There should be little heat noticed unless you have a batch with particularly low Vf, and even then, the problem with the lead size and insulative properties of the epoxy casing will not allow much heat to pass out.

If you consistently overdrive at 4.5V, you could reduce the life from the original 100,000hrs to maybe 50,000hrs, or even *gasp* 20,000hrs. Nothing much to worry about, IMHO. /ubbthreads/images/graemlins/smile.gif

BTW, the way young girls are dressed nowadays, you'd have a better chance with the area below the belt (if they are wearing those poor excuses for skirts), being that many of them aren't actually wearing a bra, but show a strange attraction to white thongs (or bum floss as we call them here) /ubbthreads/images/graemlins/grin.gif

 

[PlayboyJoeShmoe]

Re: HELP I\'m new WHY does this work?

Butt Floss is HOT in the CORRECT butt!

I don't know diddly about UV or Blacklight!

 

[php_44]

Re: HELP I\'m new WHY does this work?

[ QUOTE ]
Steelwolf said:
If you consistently overdrive at 4.5V, you could reduce the life from the original 100,000hrs to maybe 50,000hrs, or even *gasp* 20,000hrs. Nothing much to worry about, IMHO. /ubbthreads/images/graemlins/smile.gif


[/ QUOTE ]

Actually, if you ask a friendly vendor nicely, they'll tell you that honestly - epoxy encapsulated UV LEDs only run a few thousand hours till half brightness. This is due to the high flux UV light destroying both the LED die and the epoxy encapsulent.

Nichia has a UV LED in a metal can with a quartz lens, and they only rate it for 5000 hours till half brightness due to degradation of the LED die, but get probably double the life of "plastic" UV LEDs due to their expensive packaging.

In the end - even getting 1000 hours from an overdriven cheap plastic UV LED is enough for most people's usage habits. At that point - just spend another few bucks for some new ones.

 

[The_LED_Museum]

Re: HELP I\'m new WHY does this work?

There's a near-UV LED light available who advertises the LED life at 100 hours - this is probably quite accurate as the unit overdrives its LEDs significantly. Another well-known LED tester got a couple of hundred hours to halflife in near-UV LEDs with epoxy encapsulant and a drive current of 20mA. Between the die eating itself and the epoxy encapsulant going bad, that's how most NUV LEDs degrade.

Nichia NUV LEDs with metal cases and glass lenses should exceed 2,000 hours to halflife, because they don't have any epoxy to degrade, yellow, and go bad.

 

[Steelwolf]

Re: HELP I\'m new WHY does this work?

php 44: Thank you. I stand corrected.