310 nm Torch Conundrum [Solved: It is not working.]

[Andrea B.]

OK, here is a really stoopid question. I'm a bit embarassed.

 

How can I determine whether my 303 nm 310 nm UV-LED torch is actually working?

 

Shouldn't I get something recorded if I shoot directly into the torch in a dark closet so there is no possibility of ambient contamination? I don't seem to be getting anything recorded. But I don't know if this torch is actually working.

 

EDIT: make that a 310 nm torch.

[Andrea B.]

Like, will 310 nm fluoresce paper with optical brighteners as do my usual 365 nm torches? I'm not seeing that.

[Stefano]

Well... fluorescence! Also check if glass stops it.

[Stefano]

Paper should maybe fluoresce a bit? Otherwise, I am 100% sure that some minerals fluoresce under UVB and even UVC lights.

[Herman1705]

 

How can I determine whether my 303 nm 310 nm UV-LED torch is actually working?

 

 

A detector? http://www.roithner-laser.com/pd_uv.html

[Andrea B.]

I will go look for my box of rocks. I'm pretty sure I unpacked it after the move.

 

Later: Got nothing from the minerals. So the torch is not working!

 

Now to troubleshoot the problem. On/off switch? Badly wired UV-LED?

If I figure out the problem, I'll report back.

[Stefano]

A silicon photodiode, without glass on it (or with quartz or UV-transparent glass on it) should detect it. Note that a camera sensor is basically a matrix of silicon photodiodes, but you should have a monochrome sensor without UV-blocking glass on it to be able to use it like a normal photodiode.

 

Note: written before the last Andrea message.

[Andrea B.]

At this point I think I should also go look for my UVA/UVB Solarmeter. It's in one of about 25 unpacked boxes.

 

I have some of those UV beads, but they may not be all that sensitive to 310 nm. Linkie: https://www.teachersource.com/product/ultraviolet-detecting-beads/light-ultraviolet

[Andrea B.]

BTW, I tested on a calcite crystal, Willamite and Hackmanite.

 

Very cool link for mineral enthusiasts: https://www.fluomin.org/

[Andy Perrin]

"Hackmanite" is the perfect name for a rock, isn't it?

 

"Hack! Hack! I found it!"

"What?"

"Uh, Hackmanite!"

[Cadmium]

Andrea, I don't find where you decided it was not working. Can you point that out for me?

Does this happen to be the 310nm LED torch from MaxMax?

[colinbm]

Andrea, if it is working it should warm up quick enough....?

[Andrea B.]

Cadmium: Andrea, I don't find where you decided it was not working. Can you point that out for me?

Does this happen to be the 310nm LED torch from MaxMax?

 

I was not very clear, but in Post #6 above, I wrote "Got nothing from the minerals. So the torch is not working!" To elaborate, I found my box of fluorescent minerals and tried to elicit some fluorescence from them with the 310 nm torch, but got no fluorescence. And I know my calcite crystal will fluoresce at 254, 320 and 365 nm.

 

Yes, this is the 310 nm torch from MaxMax.

---

 

Col, I never did feel the torch warm up even a little bit. Dead as a doornail.

---

[Alaun]

In some of my led flashlights, the batteries go in opposite to what you would expect?

[Cadmium]

Cadmium:

Yes, this is the 310 nm torch from MaxMax.

 

Then just to make sure, did you remove the glass lens first like MaxMax says?

I quote from MaxMax:

"Note: Remove glass lens before use because lens will block 310nm UV light"

[Stefano]

Why do they put a lens that blocks UV light? Well, you need quartz or something different from normal glass to pass 310 nm UVB light. Thorlabs (and other companies) sell quartz lenses, you may find one that fits in the torch head and focuses the UVB rays. They are expensive, of course.

[Cadmium]

I don't make sense of it. They say three things, seemingly about the same intigrated torch lens,

There seems to be a contradiction about the lens, but I don't know exactly what they mean.

 

"Note: Remove glass lens before use because lens will block 310nm UV light

Zooming Focus Head

Collimating Lens"

 

I think a lot of glass does pass 310nm, even some inexpensive glass, like cheap close up filters are made from.

B270, NWG280, others, intensity varies, but those should all work.

 

I don't know what MaxMax it means. It is possible they need to edit that.

https://maxmax.com/s...-a-310nm-uv-led

 

Perhaps they are talking about a glass camera lens? Who knows. Doesn't sound that way, but...?

[Cadmium]

They have over 50 different types, all using the same torch body, apparently, so perhaps the glass lens doesn't work for those models with LED's that are below a certain nm.

I don't know, but if I were Andrea, I would try removing the lens to see if it works better.

https://maxmax.com/shopper/category/9524-xniteflashf-series-uv-to-ir

[Cadmium]

I note that all of their torches that have LED's 310nm and below all say the same "Note: Remove glass lens before use...".

However, their torches starting with 365nm LED have no such note.

Now if that means the lens on the torch or the lens on a camera? I am guessing the lens on the torch.

It would seem that their basic torch is used for all models, including the same lens, which was probably generically made to use with visual light, and they are installing their own LED's,

[Andy Perrin]

It would seem that their basic torch is used for all models, including the same lens, which was probably generically made to use with visual light, and they are installing their own LED's,

It looks like that to me also, but what an idiotic thing to do. They should replace the lens as well as the LED, not put an idiotic note on their website.

[Cadmium]

Yes, it would seem that they are saying the torch has a Collimating Lens and provides Zooming Focus via the lens,

so then if the lens needs to be removed for 310nm and below LED's, then of course it would not collimate or zoom, right?

So then those items should be removed from the list for 310nm and below LED torches.

Actually, without the lens, then I suppose the beam is not going to be the same, but that might not be all bad, because a tightly focused beam is not that good in my opinion.

It is just because they edited the original and didn't remove some of the info for the standard basic torch I think.

Wouldn't it be cool and handy to have one or two of those torches, and then a set of ALL of the LED's they use in them?

Well, depending on how easy it is to swap out the LEDs...?

[Andy Perrin]

Unfortunately LEDs aren't quite swappable (at least not without some kind of adjustment) because the wavelength of light they emit is correlated to the voltage they run at. So an ultraviolet LED needs a higher voltage than an infrared one generally, and so forth.

[ulf]

Unfortunately LEDs aren't quite swappable (at least not without some kind of adjustment) because the wavelength of light they emit is correlated to the voltage they run at. So an ultraviolet LED needs a higher voltage than an infrared one generally, and so forth.

 

There is also a big range of maximum currents they can handle.

The strong UV-LEDs in our Convoy S2 are running on something in the neighbourhood of 1A

 

UV-LEDs for shorter wavelengths can normally not handle anything close to that.

[Stefano]

Unfortunately LEDs aren't quite swappable (at least not without some kind of adjustment) because the wavelength of light they emit is correlated to the voltage they run at. So an ultraviolet LED needs a higher voltage than an infrared one generally, and so forth.

The forward voltage of an LED is, theoretically, equal to the energy in eV of the emitted photons. The reality is a bit different, but you can use this as a rule of thumb. In this example, 310 nm means 4 eV of photon energy, so you should expect roughly 4-5 V of forvard voltage. Since LEDs require a current-limited power supply, you also have to change the driver circuit. Maybe you can do that DIY with a buck-boost converter with a current limiting feature, setting the current to the rated LED current.

[Andy Perrin]

The forward voltage of an LED is, theoretically, equal to the energy in eV of the emitted photons. The reality is a bit different, but you can use this as a rule of thumb. In this example, 310 nm means 4 eV of photon energy, so you should expect roughly 4-5 V of forvard voltage. Since LEDs require a current-limited power supply, you also have to change the driver circuit. Maybe you can do that DIY with a buck-boost converter with a current limiting feature, setting the current to the rated LED current.

Stefano...I invented that rule of thumb in 2011 when I was working on my postdoc, and I published it on the board here along with some data in 2018? I am not sure why you are quoting me back to me! I suppose I should be flattered that you remember my posts that well.

 

I had actually decided against linking that old post because it's beyond what was needed for this discussion, but if you're going to quote me, please give credit.