Hey all,
Looking to get feedback on a UV flashlight that I’ve been working on for the mineral market. Curious to get the perspective of flashlight enthusiasts as it’s a first of category. I’m mainly looking for thoughts on the UI but any other thoughts are appreciated!
Make yourself at home, RaymondDashWu!
Looks like an interesting light for a niche market, though maybe rather on the large size. I would generally get the advice of other people in the mineral analysis niche on the UI rather than flashlight enthusiasts, but from what I can see having separate buttons and visual feedback on which emitter/wavelengths are in use would be useful.
Thanks for the feedback! I’m getting input from the geology/mineralogy community on separate channels but wanted to reach out here since I don’t have a great pulse on the wider flashlight space. As for the size, it is quite big but that’s about as small as I could make it for the feature set it currently has. The driver itself is 32mm (2 boost 1 linear to drive LEDs individually) and is already pretty packed. Here’s a cross section view:
The red and green seems counterintuitive. Green should mean the light is going (on); red should mean the light has stopped (off).
Welcome Raymond to BLF! That is a very interesting light, the market is kind of niche but it looks to take care of most things.
It would be a good idea to have a clear indicator what button turns on what LED, maybe have the wavelength laser engraved below each switch.
I would suggest switching the button colors, as well as making it so it can use more popular battery sizes. 21700 comes to mind, as well as the more-popular large battery the 26800.
I think this could be done pretty easily, by making the stock tube long enough for 21700 (using long springs helps compatibility), adding a 10mm extension for 26800 use, and including a set of diameter-adapting sleeves, these can be made of plastic. 21700 is similarly much higher capacity than 18650, going up to 5800mAh, and 26800 is usually available up to 6200mAh, without all the extra weight of a 32650.
The problem with 32650 is that the available cells are not able to provide much current and they are very hard to find from reputable vendors. Once the original battery gets worn out it would basically make the light obsolete, as it would be hard to replace it.
Ah I was imagining it like when you’re stopped at the traffic light. The light turned green and you press on the accelerator. Turns red and you press the brake. Either interpretation works
I was honestly thinking it would be the other way, green is “safe” (ie: no UV) and red is “danger”
Maybe you could just have the switch be 2 different brightnesses, low/high to indicate off/on and color to indicate state of charge. That way when the light is off, there isn’t much parasitic drain.
I considered having the wavelength engraved but the light will primarily be used in the dark so it doesn’t quite work out. If plastic mold costs weren’t so expensive, I’d have three switches with “S”, “M”, and “L”. That’d probably be the best.
Thanks for your advice on batteries. The idea was to make an adapter to begin with. Something like 32650 => 21700 and 21700 => 18650. It’s already long enough to fit a 21700. I posted a cross section view and because the driver is so big, the manufacturer recommended a 32650. I had no idea what it was at the time but I’m running into the reputable vendor issue you mentioned. The cell I got is labeled 7500 mAh but the two cells I got tested at ~6300 mAh. I’m guessing the same would be true of a 26800? I don’t know what Chinese brands are reputable so I generally just go with the cells from Korean or Japanese companies.
Thanks for the advice on the 5800mAh 21700! I had no idea there were cells that high capacity. I’ve been using the 5000 mAh ones. Time to upgrade!
I’ll have to see if I get that sort of feedback in person. Big gem and mineral show in January where I’ll get plenty of people to try out the light and see what they think. I do like the thought of brightness indicators instead of color. I’ll have to think about it some more. My immediate concern is that the light will get occasionally used in the day when visiting a show and it’d be hard to tell if the light is on if we’re talking low/high. Valid concern about parasitic drain though!
Generally speaking, Vapcell is a good brand of batteries for unusual sizes. @vapcell_Dennis can hook you up with samples of 6200mAh 26800 (I tested mine for some to be 6300mAh and some 6600mAh)
Part of the issue with 32650 is that the cells available are grossly over-rated in capacity and in max discharge current, so they underperform and aren’t exactly safe. At least 26800 is a relatively tested format.
For this you’ll want the LG M58T cell. All the others are kind of sketchy.
Keep in mind that it’s UV, unless the light is running at some insane intensity it needs to be dark to be useful anyways.
Also, from my own curiosity what emitters are you using?
I’ll have to see what cells my target audience has. I don’t think I even own a charger that does 26800s. I do like the idea of the LG M58T as 21700s are my preferred cell for the wh/kg. I’ve also released prior lights using 21700 cells so I may go that route.
Insane intensity. I’ve made 255nm (shortwave) UV lights where you can see the fluorescence in direct sunlight (~65k lux). Super easy to do with 365nm (longwave) LEDs. However, all my 255nm lights can at least see fluorescence in shaded daylight (~4k lux). As for LEDs, Photon Wave is literally the only company making high powered 255nm LEDs. Every other manufacturer I’ve seen is just using their dies and packaging them. 310nm (midwave) is a different story. The best UVB LEDs come from Bolb with their 295nm LED. No competition. However, I needed to match the 255nm in intensity and the target audience is used to 310nm bulbed lights so I went Photon Wave again. 365nm I just picked a cheap one from Seoul Viosys
Out of curiosity are you aware of Yingfeng emitters? They’re pretty powerful and available in UV-A, UV-B, and UV-C, in 9-die (3s3p) configuration so that a 4S white driver can be used for the long and midwave emitters (Vf≈12v). They’re just not very efficient, but few UV leds are.
Also for the 365nm if you’re going with 3535 I’d recommend the Luminus SBT-10X, it is a lot more powerful and a lot more intense than the typical 3535 365nm emitters.
Xtar sells one for pretty cheap, and a few other chargers can be modified to work.
Also, for the letter-coded switch covers, have you considered 3d-printed TPU? Not sure if it’s available industrially yet, but it makes for nice rubber parts.
Is the standard flashlight shape the best body for a light made for this application?
I would give a lot of thought to how this light is going to be used and would design it to best fit the way it will be carried when in use for long periods.
Very aware. They’re the least reputable company in the space in my eyes. They grossly inflate their radiant output numbers based on the 255nm LEDs I’ve tried from them. I highly suspect some shenanigans are going on and that their LEDs aren’t transferring heat away from the chip as optimally as possible. This is what it looks like - straight from Photon Wave’s website:
To test this out I special ordered LEDs from Yingfeng with the chip I was getting from Pwave in the same 2s2p configuration Pwave offers. Same voltage and current. Long story short - Pwave won. I can’t remember if I have recordings of it on my radiometer but it was an interesting test.
As I was saying, everyone in the space is just using Photon Wave dies so it’s just easier for me to get it from the source ¯\(ツ)/¯. However, I do have to give Yingfeng credit. They do make a lot of unique configurations as you pointed out. Much more accessible too!
Yup. Luminus make some of the best UV (A and C) LEDs. However, that’s an expensive LED. I’m also not immediately sure how to make a smooth user experience when it comes to scaling a powerful LED. It’s a bit hard for me to explain but here’s the situation: I want the users to be able to regularly reach parity with the other wavelengths at ~80-100mW. The Seoul Viosys LEDs only reach a bit over 1000mW if I remember correctly. Scaling happens over 5 seconds linearly so it’s pretty easy to time it to get to more or less the same power as the other wavelengths. However, Luminus can go up to 4000 mW. Over that same 5 seconds it’ll be very easy to miss that 80-100mW goal as the scaling is happening more rapidly (~800mW a second vs ~200mW).
I have used TPU before. It’s not a bad solution but probably a bit on the temporary side considering the thickness of switch membranes. I imagine the layers will delaminate pretty quickly over the course of a year or so. I’ll have to consult with the manufacturer but the easiest way would probably just be a sticker with the letters on them? Not that that’s ultra long lasting either. There’s some pretty crazy vinyl sticker adhesive though!
I have no idea what the optimal shape is. I would say that it’s good enough and that it’s a shape that’s in the realm of common objects. People will inherently know how to carry it in their own way. I’d prefer it over the tube and ballast lights that people are currently using!
Kind of reply/question/idea:
What happens if you mix the dominant wavelengths?
Probably hard to do in this setup but I imagined this light driven by 3 channels possible to mix.
Does blending them may bring a new effect?
It’ll activate different impurities (calcite rhomb top right pink/blue) within the minerals or the response will be stronger and emphasize other minerals (calcite/sphalerite middle red/blue). It’s a spectrum but those are the two extreme ends.
Thanks for explaining this.
I must admit your hobby (profession?) is somehow hipnotising.
I can remember when I was like 10-12 years old I liked to dig in the ground seeking for some extraordinary stones (today I would call or Mineral). Finding a meteorite was my dream then but probably I wouldn’t be even able to figure out I found one. Some years later I had Geology at my university classes and I found it very interesting.
So I probably have a weakness for… stones 
I would think that can be avoided by using SLS printing instead of typical FDM.
There’s an important improvement to make there, as perceived brightness isn’t linear. You want a ramp like the one in Anduril, where it is exponential, so that it is perceived lineaely.
