UV LED's - anyone have any experience with them?

[tomer629]

I got some 10mm LEDs from Tayda. They are labeled 10mm LED BLUE. They are clear plastic. When powered on they don't look blue, they look like UV/Blacklight.

I've read that UV LEDs can be harmful to your eyes but I was wondering if I can maybe put a filter over them like a gob of hot glue or silicone.

I've done that before with good results for these clear LEDS because they are painfully bright when looked at straight on, but if you try to dim them with a resistor they aren't bright enough when viewed from an angle.


Anyway just wanted to get peoples thoughts on UV LEDs in pedals. Anyone have any experience with them? I tried searching about if I could filter the harmful rays somehow, but all I find is stuff about using UV to filter water...

[jimilee]

I've used them in several occasions. They aren't really bright enough to do anything harmful. I wouldn't stare directly in to any LED for any length of time though.

[stallik]

Led's can give out UV. How much and at which wavelength depends on the LED. Indeed there are LEDs which are designed to give out only UV and at very high intensity. These are the kind used for scientific, security or UV ink curing purposes and are extremely bright, harmful to your eyes without protection and pretty expensive. I doubt if your ones are in this class but they may nevertheless be emmiting some. Even white LEDs can emit some. I have worked on a case where someone was using a white led torch to see what he was doing when cleaning a UV print head. The ruined heads cost some £3k to replace!
I have some decorative led strips which Emit some UV. Grab some white paper, shine the LED at it and see if the paper glows. Also, if your guitars has a modern acrylic finish, that may glow a bit green under UV. Is it dangerous? Depends on the wavelength, intensity and time of exposure so I can't possibly comment. I've had a severe case of arc eye in the past (from an arc welder) and I'd estimate that with my LEDs, it would take the rest of my life staring at them to achieve the same level of damage
UV can be filtered out. There are filters designed specifically for this purpose. I recall they were referred to as 2E filters in photographic circles. A much cheaper way to do it might be to scrounge an off cut of UV protective laminate from a graphics printer. It's a clear self adhesive sheet.  Whether you need to do the filtering is down to you

[idy]

Quick way to improve the viewing angle is to scuff them with fine sandpaper. More "diffused" now.

[Gus]

I think the use of blue and shorter wavelength LEDS is not a good idea as indicators. 

[Jdansti]

I think the use of blue and shorter wavelength LEDS is not a good idea as indicators.

True, but I once picked up a pack of hot pink LEDs and there was a UV warning on the package. If you mount the LED flush with or below the top of the enclosure put a graphic on photo paper or some other paper over it and let it shine through the graphic, the paper will probably absorb the UV. Dry urine and semen are supposed to glow under UV light, so I guess you could test it. 

[deadastronaut]

3mm uv leds are nice...little jewels....no eed for shades so far..mind you my eyes are already buggered,


john, i'll try that later..

[R.G.]

I think Gus is right.

Beyond that, there are shadings of UV. Ultra-violet - that is, beyond violet - light is light that is just beyond the human visual apparatus response. Somewhere around 400nM, light is not getting through to your retina and it starts being "blacklight". 

The human cornea and/or lens setup stops being so clear as light wavelengths get shorter. That's why black light is black - we don't perceive it much if at all, only if it makes other things fluoresce. I have read that some people who had older cataract operations to replace their lenses can actually see by long-wave UV, around 350-400nM.

Somewhere in the range of 300nM and shorter, the photons of UV light carry so much energy that they damage things. Like your retina. UV is classified into UVA, 315-400nM, UVB at 280-315nM, and UVC, 100-280nM. UVA is reasonably benign, only damaging your skin and giving you cataracts with long exposure. UVB can accumulate to skin cancer and start damaging your retina. UVC is nasty stuff indeed. Shorter than 100nM is soft gamma rays.

Germicidal lamps are low-pressure mercury vapor lamps, fluorescent lamps with no fluorescent phosphors to make visible out of UV, and quartz tubes to let the 254nM emission line of mercury vapor get out of the tube. Never, ever look at a lighted germicidal lamp. I use a 36" germicidal lamp to sterilize the water supply to my house, so I worry about this kind of thing.

"UV" LEDs are recent. Most of them are low UVA, not too damaging, but still don't expose your eyes to much of it. Cataract operations are not fun and high enough intensities focused onto your retina by your eye's own focusing apparatus can cause retinal burns.

True, but I once picked up a pack of hot pink LEDs and there was a UV warning on the package.

Many designer-color LEDs use the UVA LED and put phosphors in the plastic lens to make the colors, just like colored fluorescent and "neon" lamps.

Dry urine and semen are supposed to glow under UV light, so I guess you could test it.

Here in Texas, having a UV flashlight is a good idea for those midnight trips to the bathroom in the dark. Scorpions fluoresce strongly in UV.    From personal experience, this is a good idea.

[Jdansti]

Here in Texas, having a UV flashlight is a good idea for those midnight trips to the bathroom in the dark. Scorpions fluoresce strongly in UV.    From personal experience, this is a good idea.

They do seem to like bathrooms. I once showered with one and didn't see it until I stepped out of the tub!

[greaser_au]

Here in Texas, having a UV flashlight is a good idea for those midnight trips to the bathroom in the dark. Scorpions fluoresce strongly in UV.    From personal experience, this is a good idea.

In Australia the Slim Newton song goes: "there was a redback on the toilet seat whan I was there last night, I didn't see him in the dark, but boy I felt his bite...". The redback is the downunder version of the Black Widow, they look like  this.      Naturally you do not put your  fingers anywhere they might hide...

[duck_arse]

last time I looked in my cable-box, I saw what I think was a redback, strolling away into the dark. the cable box is under my bed. I thought the daddy long-legs's would have eaten the competition.

[stallik]

So there we have it. For health and safety's sake when dealing with LEDs, keep some scorpions handy...

[armdnrdy]

They do seem to like bathrooms. I once showered with one and didn't see it until I stepped out of the tub!

Hey John,

Was your shower experience something like this?

Hallo, wir sind die Scorpions, und wir wollen, den Rücken zu waschen!

[jimilee]

Quick way to improve the viewing angle is to scuff them with fine sandpaper. More "diffused" now.

great tip.

[Jdansti]

They do seem to like bathrooms. I once showered with one and didn't see it until I stepped out of the tub!

Hey John,

Was your shower experience something like this?

Hallo, wir sind die Scorpions, und wir wollen, den Rücken zu waschen!

Yep, and I had to clean a lot of hair from the drain!

Edit: After translating, I have to say it was their hair, not mine!

[armdnrdy]

 

[samhay]

For what it's worth, most plastic is not transparent below about 350 nm.
I doubt Tayda's supplier have used something with any really dangerous UV output, but if anybody is worried about it, I am happy to measure the spectral output of suspect LEDs in the lab.

[Ice-9]

If you have enough of the UV led's you could always make an exposure light for uv pcb, so much nicer than using the iron on method.

[R.G.]

If you have enough of the UV led's you could always make an exposure light for uv pcb, so much nicer than using the iron on method.

I thought that would eventually come up.

Yep, I did a lot of work on that at one time. In the 1990s I did PCBs with unfiltered UV fluorescent bulbs about 6"/150mm over transparencies and presensitized PCB stock. Worked.  When I moved to my present house, the setup was trashed for lack of being used. A few years ago I did some layouts for the internal effects circuits for the Vox guitars with onboard effects, and needed to once again set up a UV exposure arrangement.

I looked into UV LEDs. Doing it cheap and dirty, with poor control of exposure and collimation is easy: get a s***load of UV LEDs from ebay, hook them up in a planar array, and...

gulp... figure out some way to hold the transparency against the PCB stock. That's the tough part. I had used a foam backing back in the day, but it was not great. The good setup is to use some kind of vacuum to pull a glass or plastic cover down on the transparency onto the PCB stock. That takes some doing - and a vacuum pump.

I finally found a UV stencil exposure unit on ebay for $50. It has four UV fluorescent bulbs under a glass  exposure table, a timer and a vacuum clamp. What's not to love?

UV LEDs are a minor part of the setup to expose PCBs. But a good start. 

[PRR]

> Dry urine and semen are supposed to glow under UV
> Scorpions fluoresce strongly in UV.

Remind me not to visit *your* UV test-labs/potties.

> Grab some white paper, shine the LED at it and see if the paper glows.

With qualification. Some cheap white paper has no UV glow. Some does.

It is VERY dramatic when I throw UV on my assorted books and notes and printouts in a dim light. Some of the papers GLOW amongst the grey stuff.

Many laundry soaps and finishes have UV glow, check your washed socks.

And our Dr Strange poster.