# Why are both 365nm and 390nm LEDs used in a UV torch?



## G166H (Mar 24, 2014)

Admittedly it could be a cost saving measure but the (now defunct) "Twin-Task® 3C-UV" UltraViolet (UV) torch used both nm wavelength LEDs to cover more of the spectrum ion the UV range, but I don't know if that translates into a useful thing?

Now, I'm not shining this torch on mineral stones, I just need the UV light to detect urine. So I thought that the Longwave UV (UV-A) between 400nm-300nm, focusing on the "mercury line" at 365 would be the best option, so why would 50% of the LEDs stray away from the 365nm offering?


----------



## RI Chevy (Mar 24, 2014)

Welcome to the Forum! :welcome:

365nm and 390nm fluoresce different things better respectively. 365 is better for some, and 390 is better for some. So you get the best of both worlds in one light. 

Here is a thread about a different light that has both LEDs. http://www.candlepowerforums.com/vb/showthread.php?338893-Streamlight-Night-Com-UV-Review

Here is another with just the 365nm LED. http://www.candlepowerforums.com/vb/showthread.php?374555-Nitecore-Chameleon-CU6-(XP-G2-UV-RGB)

http://www.candlepowerforums.com/vb/showthread.php?372484-UV-flashlights-I-think-I-will-get-one


----------



## G166H (Mar 25, 2014)

Thanks, very good review. The spectrum spread offered seems to be sensible and in keeping with the "dual use" theme.

However I do like the torch, but hate the batteries, no way can I rely on those in a complete economical collapse.


----------



## Bullzeyebill (Mar 25, 2014)

Alkaline batteries? Pretty much available every where, and they can be stashed for close to 10 years. Costco has pretty good prices, and some reliable battery web sites can offer better deals.

Bill


----------



## G166H (Mar 27, 2014)

I was looking to standardise all of my batteries to AA and AAA. I think I might well go with the TK-566 instead, the extended version?

However, does Eneloop have CR123A sized batteries? (http://battery-ph.com/sanyo-battery-eneloop-aa-cr123-alkaline.php)


----------



## Chenery88 (Mar 27, 2014)

I have the TK566 and am pleased with it...lights up a small room if ambient is low and picks out stains...also very good at checking UV on banknotes... Gets warm at the head compared to a decent normal led torch but not been an issue as it is not on for extended periods...


----------



## G166H (Mar 27, 2014)

Interesting, heat wasn't something I considered an issue with LEDs, it not something I noticed in any review of any UV torch I read.


----------



## Chenery88 (Mar 27, 2014)

G166H said:


> Interesting, heat wasn't something I considered an issue with LEDs, it not something I noticed in any review of any UV torch I read.


Led torches definitely get hot....the TK gets warm quicker than my other lights...I think it is because it is not quite as solid so the amount of metal available to dissipate the heat is less...but as I said it's not uncomfortable after 10-20 mins...but is noticeable. I would recommend it as a good value UV torch.


----------

