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Huh???Why not? Couldn’t you just change the resistor on the pwm circuit to provide a higher voltage across the series. It’s not a good design but it will Work until you get thermal runaway
https://forum.allaboutcircuits.com/register?next=registertoviewA LED driven with a constant current will dissipate I*Vf Watts. If it has a resistor in series with it, the LED dissipation will be I*Vf, but the resistor wastes an additional I*Vr Watts, where Vf is the forward LED voltage and Vr is the resistor voltage. Just wasted power in the resistor because it can have no influence on the LED power...
Thanks for the review, I'm a little late to the discussion but have bin looking @ these leds. Now that it's bin a bit sins you've had them. do you still like them?Was hunting around ebay for light strips, and found:
54w/81w/108w PopularGrow Blue White LED Aquarium Light Bar Fish Tank Plant Coral
sold by ledlightplant
So here is a quick review:
I picked up 2 of the 81w version. It's just shy of 3ft long. It arrived quickly via DHL, (less than a week), and was packaged super well. No damage at all. Comes with a few small swivel brackets for mounting to a wall or canopy, and two tiny eye bolts. There are 4 captive nuts in basically a T slot that slide around freely, so you can position the brackets wherever you want, or remove them and use the little eye bolts for wire hanging.
They claim it's waterproof. Didn't actually test it, but the quality looks good. All the seals look correct, the little power supply has one of those watertight screw connectors with an o-ring.
Comes with a simple instruction page printed in english and german. Instructions were readable and generally useful, but the whole thing is basically "plug it in, make light". It's not dimmable with the supplied power supply. Ebay listing doesn't mention this, but the instructions do, LED breakdown is:
Overall, I'm pretty impressed. For a cheap ($67 US) light strip, it was made well, and lit up nicely. I question the usefulness of the greens, and kinda wish it didn't have them, but eh. Was easy enough to assemble, and the brackets screwed into my wall nicely. I mounted mine about a foot over the aquarium, and replaced 120W of DIY stars that I had built about 4-5 years ago, that started failing, because I did a terrible job of it.
- 12 white (10k)
- 9 blue (470)
- 3 UV (430)
- 3 Green (520)
Mounted at 1 foot, I'm pretty happy with the spread. It really lit up the tank. I just needed these to supplement the big lights on my 120G, which they did quite nicely. Good spread, good color, my corals pop a little more, and I'm good.
I also tried them out on my 800, because I'm looking to fill in a few holes in my lighting where the spots don't have good coverage. I tried just setting them right on the top of the acrylic in the front of the tank, where there is very little light, and they lit the bottom up nicely (3ft deep). Purely aesthetic at that depth, but it looked good. Being only 3" off the water though, you could make out the individual colors in the water at the top of the tank, so, not ideal, but they at least were able to illuminate the bottom sand at 3 ft.
Also tried them out in the back of the big tank. Took a PAR measurement with the main lights on 25% in a bad coverage area (basically getting ambient light) and read 60. Put the lights right on the 1" acrylic over that spot, and at 1 ft depth, read about 130. This was just with a single 3ft bar. Not super powerful, but the area looked good visually.
I'll reply to this post later tonight with some pictures of the 120 with the lights powered up. Overall, I'd say these are a good value. I suspect if you got enough of them, they would be decent lights. Just one is purely aesthetic, but I'm OK with that for this use. I will probably buy 2 more of the 21" ones for use on my QT tanks, and maybe 2 more of the 48" ones for some supplemental lighting on my 800. (still debating the 800).
Hope this is helpful to someone. I have no connection to this seller, just relaying my experience.
Thanks for all the info you shared here. I'm waiting on 2 medium size bars arriving at the moment. On the ones you received, what size is the fixing point on the bracket? I'm going to start thinking about possible mounting options while I wait for delivery.So just kind of a longer term update to this ancient post. I've had them installed since Feb 2019, so almost 2 years.
The ones on the QT tanks, (4ft version), still doing great, but I use them sporadically, so, far less usage.
The ones on the 120g tank (3ft version), have been in use every day for about 10hrs a day. One of them gets alot of salt spray. Zero problems, still light up, still provide light.
Overall, I'm happy with them.