(Coronavirus) On UV Sanitization

[linux-works]

I would just cancel that bulb order. if its led, its fake. done. no need to waste time. I'm quite sure all are fakes.

at that price, it can't be true that they are real uvc leds.

plus, the output would be too weak to be useful.

pure scam ;(

 

[Alan Kk]

I have heard and read a wide range of exposures for killing Covid-19 and SARS. I have been using this study, which isn’t perfect but seems close to our application:

Inactivation of viruses on surfaces by ultraviolet germicidal irradiation. - PubMed - NCBI

They say, “For 90% viral reduction, the UV dose was 1.32 to 3.20 mJ/cm2 for ssRNA,” … “For all four tested viruses, the UV dose for 99% viral reduction was 2 times higher than those for 90% viral reduction.”

Covid-19 is an ssRNA virus so 99% dead takes 6.4 mJ/cm2 or 64 J/m2 of UV-C exposure.

I am hoping to find good info so please comment if you have other sources and different data.

 

[joetomasone]

I would just cancel that bulb order. if its led, its fake. done. no need to waste time. I'm quite sure all are fakes.

at that price, it can't be true that they are real uvc leds.

plus, the output would be too weak to be useful.

pure scam ;(

There are indeed real UVC leds - the question is whether these are UVC and indeed what the output is. That's the idea.

I was pretty sure that the Chinese phone disinfectors I ordered were NOT UVC and were plain old lights - but the meter doesn't lie - they are legit. Not a fantastic design, but legit.

 

[eevee-fan]

I would just cancel that bulb order. if its led, its fake. done. no need to waste time. I'm quite sure all are fakes.

at that price, it can't be true that they are real uvc leds.

plus, the output would be too weak to be useful.

pure scam ;(

Tried to cancel and the seller account had disappeared. Waiting required # of days before reaching out to eBay for refund via buyer protection.

 

[eevee-fan]

Any thoughts on these devices? I see some models here with seemingly LED light sources. Wondering if they're real UV-C.

7 of the best UV cleaning devices to disinfect your home

 

[linux-works]

one thing I'm hearing from people who have some experience, is that uvc leds DO exist but they are so expensive, china items likely will all be fakes.

and, uvc leds are all out of stock (a friend tells me) due to the rush on the market.

given the fact that its also very hard to validate these 'products', I would assume all are fake and worthless unless specifically proven otherwise, and even then, the next manuf run may use different parts.

its hard to fake bulbs; but with leds, I would not even waste my time anymore.

 

[joetomasone]

one thing I'm hearing from people who have some experience, is that uvc leds DO exist but they are so expensive, china items likely will all be fakes.

I bought a Homedics phone sanitizer for $80 that includes two UVC LEDs.

I don't recommend the design since they don't have enough coverage at the distance the phone lies away from the LEDs (the space on the phone midway between the LEDs gets significantly less mJ/cm2 and it only runs for 30 seconds at a time - not nearly enough to do the job at the power output it has), but they ARE indeed UVC LEDs nonetheless.

 

[eevee-fan]

I bought a Homedics phone sanitizer for $80 that includes two UVC LEDs.

I don't recommend the design since they don't have enough coverage at the distance the phone lies away from the LEDs (the space on the phone midway between the LEDs gets significantly less mJ/cm2 and it only runs for 30 seconds at a time - not nearly enough to do the job at the power output it has), but they ARE indeed UVC LEDs nonetheless.

So I wonder if those fake LED UV-C corn bulbs actually have 5 actual UV-C LEDs... one on each of 4 sides plus one on the top. Would be neat if someone had a meter and can measure it.

 

[eevee-fan]

Hm... looks like those UV-C light in air handlers have some considerations too...

HVAC UV Lights for AC Systems-Do They Work? - House So Green

 

[EVCollies]

I purchased one of the corn cob bulbs on Amazon and after reading this report I requested a refund stating did not emit UVC. The refund was immediately given without a request to return the item indicating the seller acknowledges it was a fake.

If anyone wishes to test it, let me know.

 

[eevee-fan]

A Jan 2019 article talking about LED and UV lights... because there was a myth that LED emit UV-C... summary, it does not.

Don’t get burned about LED UV - Power Electronic Tips

 

[eevee-fan]

$5 hack to build a UV-C measuring device.

Measuring UV-C For About $5

"NukeMeter is a device that allows you to measure the intensity of UV-C light put out by standard germicidal bulbs. It relies on a low-cost sensor and some open source hardware and software. For the prototype in this HOWTO, total cost in materials is ~$2.50 for the sensor module and around $3 for the Arduino-compatible board if you get them off eBay."

 

[joetomasone]

I purchased one of the corn cob bulbs on Amazon and after reading this report I requested a refund stating did not emit UVC. The refund was immediately given without a request to return the item indicating the seller acknowledges it was a fake.

If anyone wishes to test it, let me know.

I’ll test it. I have a UVC meter. Will PM you.

 

[joetomasone]

So I wonder if those fake LED UV-C corn bulbs actually have 5 actual UV-C LEDs... one on each of 4 sides plus one on the top. Would be neat if someone had a meter and can measure it.

That’s what I will be doing when the one I ordered finally arrives.

 

[eevee-fan]

 

[linux-works]

my meter should be here today

I have a corncob bulb so I'll do a test. I do have many other real glass uvc bulbs so I'll take a strength reading from them, too, just to compare.

note, though, that even uvc meters will still have overlap with some other bands, so unless you have a very tight bandpass filter, its going to be hard to say how much A/B/C components are in a wave. prices for actual frequency reading spectrum meters are $1k and upwards, so even less likely we can know that much about our lights.

the meter I bought will have both A and C sensors but still, they are not tight bandpasses so its still going to be hard to say, for sure, how much C is in any given wave.

 

[linux-works]

$5 hack to build a UV-C measuring device.

Measuring UV-C For About $5

"NukeMeter is a device that allows you to measure the intensity of UV-C light put out by standard germicidal bulbs. It relies on a low-cost sensor and some open source hardware and software. For the prototype in this HOWTO, total cost in materials is ~$2.50 for the sensor module and around $3 for the Arduino-compatible board if you get them off eBay."

I started with that guy's article, but I think my sensor project takes it up a level or two.

sadly, I followed that guy's idea too closely and ruined one of only 2 of the purple generic boards I have. in fact, leave the resistors ALONE on the purple generic board! they are FINE the way they are, even better than adafruit's. adafruit uses 1 op-amp as a gain stage but the generic one uses a dual op amp and uses both.

when I run both sensors, the adafruit one puts out values in the 4.0 range (out of 1023) and yet I get 150 and higher counts from the generic dual-gain sensors.

when I flood both with real uvc, they both go 'very high' and that's really all you need.

both adafruit and the generic (and all others in that price point) use UVA sensors and that's why the product is 'GUVA' part numbered. I plan to swap out the A sensor with a true C that I bought at digikey and see if it still works (it should, same basic diode sensor, same interface and output interface style). the trick is to remove the old one and install the new without overheating it (smd and I'll have to keep the hand soldering to a min).

tip for those that want to do it right: a special solder called 'chip-quick' (check the spelling) is helpful to unsolder things if you want to be extra careful. its solder that holds liquid/hot form for a very long time; you load up the existing part with the CQ stuff, let it sit there and 'sink in' for a few seconds, then just lift the old part out with tweezers and wipe away the remaining solder and CQ. its expensive but so are the boards and sensors, these days if you order the sensor from digikey, might as well consider some chipquick as well. (I usually order from mouser, but they don't have any of the uvc parts, at least any that I could find).

 

[linux-works]

oh amazon, why do you keep showing me things that just lighten my wallet?

found one of these on sale so ordered one:

https://www.amazon.com/dp/B002JOR0JO

there was an open-box or 'refurb' (who knows) for under $100 so I grabbed it. if its in bad condition, I'll just return it, but for the price, it might be useful to have a 2nd reference (not C, though).

its a common meter; general is just the label but if you search, you'll find many 'brands' use that same shape and button,display layout. same design inside, too, no doubt. all the expense is in the sensor, anyway, not the meter.

 

[linux-works]

got my meter today!

did a test with a real uvc glass bulb and the corncob fake thing.

yup, corn is fake alright.

here's the datalog output; the meter logs to sdcard; I then copy the .xls file to my pc, run a spreadsheet prog on it and you can see where the left data set shows uvc data (I set the datalogger, left the room, used an RF remote to trigger the bulb, let it run a while, then turned it off).

there's some quiet time at first (I did that to get a zero baseline), then there was about .2 mw/cm2 average reading for the time I had the bulb on, then when off, value went to zero. so, meter works

sheet on the right (smaller one) shows the corncob led light. I started the test with it off, used the same RF remote base, turned it on for about 10 seconds then off and then stopped the test.

no uvc values at all for the corncob. CONFIRMED.

sensor was about 3" from the light. even if the led is not as efficient, I should see SOME output.

nothing.

glad I got my money back from the seller.

 

[joetomasone]

oh amazon, why do you keep showing me things that just lighten my wallet?

found one of these on sale so ordered one:

https://www.amazon.com/dp/B002JOR0JO

there was an open-box or 'refurb' (who knows) for under $100 so I grabbed it. if its in bad condition, I'll just return it, but for the price, it might be useful to have a 2nd reference (not C, though).

its a common meter; general is just the label but if you search, you'll find many 'brands' use that same shape and button,display layout. same design inside, too, no doubt. all the expense is in the sensor, anyway, not the meter.

That's UVA and UVB. Useless for UVC. I have the same meter. I used it to check which glass on my Model 3 was UVA-protected (side windows are not) and to evaluate how good the tint job I had done on those windows worked (excellent).