UV LED for mineral fluorescence

stringtyer

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I've re-entered the world of metal detecting which has led to other "treasure hunting" activities. Many of the things I do are for fun but most are done because I want to teach my grand-daughters to love outdoor adventures rather than burning brain cells in front of a video screen. They love going metal detecting with Papa (me) and enjoy going gold panning and creeking for cool rocks. To that end, here is my problem/situation ...

I have an old Fenix PD30 flashlight that I rarely use and want to see about converting it to use a UV source for checking rocks and minerals for fluorescence (and for finding "spooky" insects at night). I'm looking for advice about my project.

Is the project feasible and, if so, what would be a good LED to use for the replacement?

Thanks for any advice offered.
 

lava

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I am a fluorescent mineral collector and have a number of UV LED lights. If you don't have a Convoy S2+ 365nm flashlight with ZWB2 filter on it, you must get one asap. With filter they're only around $25-30:

https://www.banggood.com/Convoy-S2-Nichia-365nm-UV-LED-1Mode-OP-Reflector-Flashlight-p-1024097.html
https://www.banggood.com/365nm-UV-Flashlight-Visible-Filter-Lens-1pcs-p-1015970.html

I also have a homemade 340nm resistor drive light, and 305nm and 278nm flashlights with custom boost drivers. I have a friend who works at an OEM flashlight company and made the latter two for me. I am trying to get into doing it myself now. The problem is that beyond 365nm, these LEDs are not efficient and require Vfs up to 7-8V. I am currently in the process of trying to find a boost that will ingest single 18650 voltage and output 350mA @ 4.2V, and am not having much luck so far.
 

stringtyer

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I've been digging around this forum and other sources and think my best option is to purchase a purpose specific UV light. After looking at the info on disassembling/modding a Fenix light, I think all I would be doing is ruining an otherwise good light.
 

PhotonWrangler

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I've been looking for the Woods Glass style UV filters and couoldn't find any (thanks Lava). So I bought a Rosco dichroic UV filter for my Nichia-retrofitted Trustfire light and the filter works well. I've been looking for a better LED source because the Nichia output is somewhat splotchy.

Also I keep hoping for some breakthroughs on shortwave (UVC) LEDs. There are some available but they're still pricey and probably fairly weak. While there are some minerals that fluoresce beautifully under longwave UV, shortwave is where most of the action is at, and for now it still requires a UVC fluorescent lamp with a Woods filter in front of it.
 
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HarryN

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It has been a while since I looked at UV LEDs.

Interestingly, Lumileds has some fairly decent ones in the 380 nm range - under their UV U line of products. Also - un domed.

Thorlabs sells some in the 250 nm range. In fact they have a complete offering of optics, mounting tube, etc. It is sold under the section "High-Power UV LEDs with Ball Lens"

It is approaching a $1K even to do a fairly complete package, but stepping back for a minute, I remember in the past spending $3K in parts, experimenting and figuring out optics for LEDs, so maybe it isn't such a terrible price after all.
 

MTRun!

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Reviving this question - has anyone found a pocket short wave UV (254-265nm) flashlight for minerals recently? The only thing close I have found is on Ledwv who sells a "UVC LED Flashlight 265nm @10mW". Never heard of the company. Or are people just making their own shortwave UV flashlights? Any thoughts are appreciated.
 

MTRun!

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True shortwave UV emitters are still pretty uncommon and expensive.

Reading a lot of the other threads, that is what it sounds like. It seems people have found some sources through the aliexpress or digikey routes for bare LEDs, but given the lack of short wave UV LED lights, perhaps the price, output, lifespan and safety concerns haven't been solved yet.
 

MTRun!

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365 nm with Woods lens from HDS

I really would love one of these. The 365nm is long wave, great for scorpions and some minerals, a 254nm (short wave UV) to cover the rest I am curious if we can find or build.
 

PhotonWrangler

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I have a couple of UVC LEDs mounted on stars now. I got them from Digi-Key for $20-something per unit. I need to find the right driver and host for one. I also need to test one of them with some UVC reactive fluorescent minerals to get a feel for how bright they are.
 

MTRun!

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I have a couple of UVC LEDs mounted on stars now. I got them from Digi-Key for $20-something per unit. I need to find the right driver and host for one. I also need to test one of them with some UVC reactive fluorescent minerals to get a feel for how bright they are.

Wow, it sounds like you have your work cut out for you. But glad to hear you are saying there is a chance. Balancing the ability to power, and drive the LEDs as well as whether the output at that wavelength is high enough to be useful sound like you understand the challenges. Would love to hear any updates as you experiment.
 
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creative_bureau

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Reviving this question - has anyone found a pocket short wave UV (254-265nm) flashlight for minerals recently? The only thing close I have found is on Ledwv who sells a "UVC LED Flashlight 265nm @10mW". Never heard of the company. Or are people just making their own shortwave UV flashlights? Any thoughts are appreciated.

This one is 265 and made in USA. https://www.instagram.com/p/CGdVp-BlrzA/?utm_source=ig_web_copy_link
 

DIWdiver

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Uh..... Not sure how that relates to the question about a "pocket flashlight".

The link you posted provides no useful information about specs, manufacturer, where or how to buy it, or even how to search for information about it. Any more info available?
 

PhotonWrangler

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It looks like it's unfiltered so it would still need a UVC-passing woods glass filter. The 254nm UVC LEDs that I have put out some visible blush-white light which would reduce the contrast in mineral fluorescence without a filter.
 
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