Adding UV led's

[dodgy67]

I have built my own led fixture for my 44 inch tank running two strings on two 6 way switches, CW and Blue sw1 are Cree and RB and CW on sw2 are Rebel.

I am thinking of adding a UV string and have found the only uv led on Ebay is Epistar but they only give off 20lm whereas the other Epistar colours are around 200lm each, normally I run 12 to 14 led's in one string, can anybody tell me how many UV led's should I be running, will be either with a Blue or RB

 

[mcgyvr]

What driver/power supply are you planning on running for this string of UV?
What is the forward voltage rating and current rating of the UV leds?

 

[dodgy67]

Adding UV ldd's

Adding UV ldd's

Forward voltage is 3.6 to 3.8v running at 700ma driver is a Meanwell lpc 35-700

 

[mcgyvr]

LPC35-700 is rated to overcome up to 48V drops so
48/3.8 = 12.6 so you can run up to 12 UV LEDs..

Note: I suspect 700mA may be a bit much for the UV LEDS.. 350mA may be better.. They typically can't take the current like a normal color LED can due to the short wavelength just burning them/lens up..

 

[dodgy67]

The led's are rated 600 - 700ma I was really wondering due to their low output of only 20lm should I be running more than 12 as I have two drivers running most times and a spare so could run a string of RB as well

 

[outssider]

LPC35-700 is rated to overcome up to 48V drops so
48/3.8 = 12.6 so you can run up to 12 UV LEDs..

Note: I suspect 700mA may be a bit much for the UV LEDS.. 350mA may be better.. They typically can't take the current like a normal color LED can due to the short wavelength just burning them/lens up..

+1
uv burn the lenses after several months if you run them high. You'd be better off running them lower and run more than you originally thought

 

[gus6464]

The lens burning is only true for the cheap diodes. If you buy SemiLED or Luxeon UV you will not have this problem. Rapidled has good bins of the semiled 420nm and 410nm right now for a quality diode at a good price.

 

[Ron Reefman]

The lens burning is only true for the cheap diodes. If you buy SemiLED or Luxeon UV you will not have this problem. Rapidled has good bins of the semiled 420nm and 410nm right now for a quality diode at a good price.

Am I right or wrong about this? 410nm and 420nm are not UV they are violet. Light them up and you can see the light... that's not UV.

 

[jedimasterben]

They typically can't take the current like a normal color LED can due to the short wavelength just burning them/lens up..

Heat is not the cause of lens degradation, it is because they use PMMA instead of silicone. PMMA is a plastic and like basically all plastics is degraded by high energy near-UV light. Almost all Chinese violet LEDs peak at 405nm, so enough of their light is high energy enough to destroy the plastic lens.

The lens burning is only true for the cheap diodes. If you buy SemiLED or Luxeon UV you will not have this problem. Rapidled has good bins of the semiled 420nm and 410nm right now for a quality diode at a good price.

This.

Am I right or wrong about this? 410nm and 420nm are not UV they are violet. Light them up and you can see the light... that's not UV.

Correct.

 

[gus6464]

Am I right or wrong about this? 410nm and 420nm are not UV they are violet. Light them up and you can see the light... that's not UV.

Right. Light from 400-430nm is really violet with 400nm being characterized as near-uv. Even if they are not UV cheap diodes have crap lenses on them which is why they brown out after a while. The original maxspect razor was notorious for this on their violet channel as they used really crappy violet diodes.

If you want a quality violet diode stick to SemiLED. Luxeon UV is the current king when it comes to output efficiency but it is considerably more expensive. The "UV" part in the Luxeon is just what they call all the diodes in the range even if some parts are not true UV. They have bins from 380nm to 430nm.