I’m new to the forum and new to modding flashlights, so I am not really knowledgeable enough to figure this out myself, but I’m guessing someone here is. I’d really like to make a legit UV-C sterilization flashlight, to use on things like door handles and other surfaces I have to touch. I might even EDC it and use it on pin-pads and crosswalk buttons as I use them. I see that UV-C LED options are extremely limited, and I’m not sure how to make proper use of what is available. Mouser and I believe Digikey have some options with the correct wavelength (<300nm, optimally 265nm). Anyway this isn’t exactly a question but more of a request that I am putting out there. Can someone build and test a UV-C light, and write up a parts list/build guide? You would be doing a service, I think, to anyone on BLF that would own a UVC sterilization light if they could. I realize this is a significant request, but I’ve been looking everywhere and I can’t find a trustworthy UVC sterilizer and I don’t quite have the knowledge to build one myself (yet). I’d love to see a discussion, does anyone think this is a good idea? Is there some problem I with this that I am not seeing?
My advice: dont do it. I wasted so much money trying to do it… and then in order to test the UVC you have to spend more money to buy something to test it only to tell you it doesnt work…
As you know UV-C is dangerous for the eyes and skin. This includes you and other people around.
UV-C produces ozone, which is also harmful
UV-C breaks chemical bonds, exposed surface might age and degrade faster.
UV-C does not instantaneously sterilize surfaces. You need to keep shining the light on the surface for some time to kill everything. Also, microbes may still survive in asperities where the light didn’t reach.
If there is any dirt, dust, or bio-film the microbes are much harder to kill.
It is much easier to:
Wear gloves when you know you will touch infected surfaces like door handles
Use your knee or elbow for crosswalk buttons
Wash your hands. Soap kills microbes much more reliably than UV-C
Use disinfectant whips.
Unfortunately UV-C is far from being a “magic bullet” that will keep the world safe against microbes. In fact it does more harm than good in most conditions.
Building a UV-C flashlight is not actually difficult - it just looks like a high V_fwd LED. There are lots of drivers (with the appropriate voltage and current) which can drive UV-C LEDs. The tricky part is to get the appropriate UV-C LEDs at reasonable costs. Sub 280nm LEDs are available, but 265nm and lower wavelengths begin to get very expensive, tens of dollars per LED, increasing significantly for higher power levels. Side note - this also means most of the 'cheap' UV LED 'disinfectant lamps' you can get on Aliexpress etc, are not actually germicidal, and produce UV in the higher wavelengths (>300nm) which would not be anywhere near as effective as true 265nm or lower UV-C light.
In addition to all the dangers described above, even if you're looking to disinfect surfaces with such a flashlight, you're looking at tens of minutes to achieve proper sterilization, which I assume would render such a device too expensive for limited practicality. I'm pretty sure you wouldn't want to be waiting around your door knob for 10 minutes shining a light on it before opening the door! Water sterilization with UV is different since the water is continuously exposed to UV for a long duration of time.
It looks like it takes between 50 and 150 mJ/cm^2 to disinfect different bacteria, spores and viruses by a factor of 10^4. (Search “uvc dose to disinfect”, informative PDF is second hit)
So for a light with 10 10mW LEDs, say 60mW can be concentrated into a 5cm spot, so 20cm^2. That makes 3 mW/cm^2 intensity. So to give that 5cm spot a 100mJ/cm^2 dose it would take 33 seconds. Not too bad.
With the UVC steripen it disinfects a liter of water in 90 seconds.
They have UV-C light wands available on Amazon for about $50. My company bought a bunch for it’s employees when we returned to work. Usb rechargeable. From everything I have researched, they work well.
I can’t link it without linking my Amazon account and that’s not going to happen lol. But I did find it, you can search Lovcoyo uvc wand. My employees have been using it for a few months now and we have had zero issues.
