LED / Electronics Experts Needed

redfishbluefish · Jul 10, 2018

I'm an idiot when it comes to electronics, and dumb enough to still try and fix things, even though I don't know what I'm doing.

I have three very nice LED lights (By Fathom, now out of business) that eat the UV beads....starting at about every six months or so. The bead that is in there is a 3 watt LED. What I'd like to know, if I replace it with a 5 watt LED, will it work and will it last longer. My pea brain is telling me that an LED that can "accept" more power will last longer.

The 3W chips have forward voltage / forward current of 3.6-3.8 v/ 600-700mA, and the 5W that I'm looking at (HERE) are 6 - 7 v / 700mA. And I don't care if it's not as bright, just as long as I don't have to pull these out again, or with such frequency.

Thanks, Paul

chipmunkofdoom2 · Jul 10, 2018

The 5W LED should work in the setup. The big thing is the current, and it looks like the 5W LED draws the same amount of current that the 3W diodes do. I think most LED lights in the hobby use constant current drivers. This means the current supplied to the string is constant (say, 700 mA) while the voltage can vary to accommodate different amounts of LEDs. If this is the case, the LED driver/power supply should put a little more voltage into the string to accommodate the 6-7 Vf of the 5W LED.

The only other thing you'd want to check is that the power supply can provide enough voltage to power the 5W LED. Do you have any pictures of the drivers in your LED light? The technical specifications on the driver would probably list an output voltage range. It more than likely can spare an additional 2V, but it's always good to check.

Crabs McJones · Jul 10, 2018

What is your power supply? How many LEDs are you replacing? My only concern is that the leds are going to try to draw more power than your power supply can give them

oreo54 · Jul 10, 2018

Need to know the cumulative voltage of the string that includes the new violets..

BTW: Probably not gaining anything w/ the 5W since in all likelihood it's just 2 "3W" chips in series..
Actually doubling the problem.. since you will be at the same current but double the output.

redfishbluefish · Jul 10, 2018

chipmunkofdoom2 said:
........The only other thing you'd want to check is that the power supply can provide enough voltage to power the 5W LED. Do you have any pictures of the drivers in your LED light? The technical specifications on the driver would probably list an output voltage range. It more than likely can spare an additional 2V, but it's always good to check.

Thanks all for the quick replies.

This fixture is not your typical fixture with the black rectangular shaped power supply. All the electronics are exposed when you remove the top plastic lens cover. Here's what you see.....that's all of it, with the exception of a fan on the back side. The one bead in question is the one with the lens removed.

redfishbluefish · Jul 10, 2018

Crabs Mcjones said:
What is your power supply? How many LEDs are you replacing? My only concern is that the leds are going to try to draw more power than your power supply can give them

See above post for power supply....all electronics exposed.

Only replacing one. Each side has two UV beads, and most of the time it's the first one in the string that blows. The other UV bead is in the bottom row with the different lens.

redfishbluefish · Jul 10, 2018

oreo5457 said:
Need to know the cumulative voltage of the string that includes the new violets..

BTW: Probably not gaining anything w/ the 5W since in all likelihood it's just 2 "3W" chips in series..
Actually doubling the problem.. since you will be at the same current but double the output.

Actually it appears to be four chips in the bead. Are you saying this isn't going to help my problem?

redfishbluefish · Jul 10, 2018

A bit more information, if this helps. On each side of the electronics you have three rows of five LEDs each. The center row are whites running at 5 W, while the the top and bottom row are the colored beads all at 3W.

Mark Gray · Jul 10, 2018

I don't think it will hurt you, how many LED's in the fixture are UV if more than 1 do they all go out at the same time? if so it maybe be the chip driving them. I doubt a 3 watt diode pulls much different than a 5 but I might be wrong, and if your whites are 5 watt I think you should be ok. I just was looking through your build thread wow you used to use the Old Icecap blasts, so did I still have one but not in use.

Mark Gray · Jul 10, 2018

Next question is there only 1 UV I didn't read you last post till now ok you have a chip driving you 5 watt row I think and 2 others driving your 3 watt rows, is it just the one diode that goes in the row? or is it the diodes that are closest to the board that are going out?

oreo54 · Jul 10, 2018

"Watts" is really a "grouping" you need to know the V(f) Actual and current to consider watts..
Example black boxes use "3W" leds and 500mA -ish drivers. V(f) is roughly 3.6V soooo 1.8W

The type of plastic is the driving force.. so unless it's better .. no it's not going to really "help" unless the new chips use better lenses..
better heat transfer ect..

you may delay the inevitable if under-driven but probably not by much.. and if constant current (which it looks to be, getting driver chip #'s would help)
it will drive at the same power anyways.. sort of.. well the chip multipliers thing 1 diode vs 2 diodes vs 4 diodes at say 350mA

guessing the IC by the chokes (331) is the driver chip.

Gets complicated w/ 4 chips.. 4 in series (4x V(f) @ current of driver), 4 in parallel (V(f) and 1/4 @ current of driver per chip), 2 par/2series ( 2x V(f) 1/2 driver current each chip)ect.

BTW: is it UV or violet and what nm is the orig?

sure there is no brick powering the driver/logic circuit board?

Output : 30VDC 3A

dug a bit..
https://www.marineaquariumsa.com/threads/introducing-the-pharos-90w-cree-wireless-modules.42698/
BIT more..
https://www.reef2reef.com/threads/fixing-a-fathom-led-fixture.283583/

you've been down that road b4 I see..

to be honest.. hope for better more current violets (btw not UV) or just switch to Royal blue (stable) chips.

OR go "deeper" into the violet..
https://www.dhgate.com/product/10pc...cinfo=17,null,1#svh-1-5|null:null:r0920228125

now there is still the driver current to consider...

redfishbluefish · Jul 11, 2018

My gosh @oreo5457 , you did some digging. And yes, I documented the original fix of (I think) nine fixtures. I recently put three of these over my tank while I waited for my new SBReef fixtures to arrive. So I'm back in business with the SB's over the tank.

So anyway, I guess good news in a way....and maybe I was premature in my assessment of the 3W LED's. This is the second one I've had to replace and I just discovered that this one is an original manufacturer's beads....not one of my replacements. I know this because they used thermal ADHESIVE, while the replacements I did used thermal GREASE. So only one of my original beads blew...and maybe it was my lousy soldering job. Anyway, up and running again (whites purposely off).