LED Drivers

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dpitalo
Posts: 39
Joined: Mon Dec 12, 2011 6:45 pm

LED Drivers

Post by dpitalo »

I'm staring to plan out my LED setup for my 40g. Here's the setup so far.

24" Heatsink 12" off the water.

36 - XP-E Royal Blue's on 3 - Meanwell 60-48p drivers
12 - XP-E Cool White's
12 - XP-G Cool White's

I'm debating right now splitting the whites into 4 separate channels to have a rolling cloud effect across the tank. I'm not sure what drivers to use though. I can't seem to find a Meanwell driver that's designed for 6 LED's, so I'm doing some reading on the Buckpucks. What I don't understand is how they're powered. From what I understand, I'm going to need a separate power supply for them...is that correct? There's also the inventronics drivers which appear to be similar to the Meanwell's as far as how to connect/wire them.

Ideally here's what I'd like the white's configured like.
12 - XP-E Cool Whites split between 2 drivers
12 - XP-G Cool Whites split between 2 drivers

Any recommendations?

Thanks!
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: LED Drivers

Post by rimai »

If you go with buckpucks, use the newer ones. They are called FlexBlock or BuckBlock.
I think this is what Deckoz2302 is using.
There has been some known issues with the old ones.
Or you could go with Meanwell ELN-30-24 for 6 LEDs.
Roberto.
dpitalo
Posts: 39
Joined: Mon Dec 12, 2011 6:45 pm

Re: LED Drivers

Post by dpitalo »

Any ideas what the issues were? Or what was the controller trying to do when an issue presented itself?
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: LED Drivers

Post by rimai »

The issue was noise being generated from the buckpuck and being introduced to RA through GND.
The old buckpucks have GND and the LED- on the same wire and I think that's what was causing the issue.
I had to create a special opto-isolation board to isolate the RA GND from the buckpuck LED- and that solved the problem.
Roberto.
rufessor
Posts: 293
Joined: Tue Oct 25, 2011 7:39 am

Re: LED Drivers

Post by rufessor »

I just finished an LED build.

Using Meanwell drivers.

One thing I would add or perhaps just detail. Be sure your not setting yourself up for poor dimming performance in the following way.

IF You run a meanwell driver using the lower end of the possible drive voltage range.

I.E. ELN60-48P runs from about 24-52 Volts output.

And do this, which is what I did, run it with 8 XP-G which require MAX 3.5-3.6V at 1500 mA your max voltage draw is just barely above the 24 V lower range. When you dim you lower current and if you look at the Cree product pages you will see that the XP-G actually have a fairly steep Voltage drop at lower currents. XP-E is less of a drop (I have NO T A CLUE WHY)

ANyhow, for me, and this just what I think.. this has resulted in very poor dimming performance wherein when I go below about 22% the XP-G whites flicker. So I am replacing these power supplies with the lower rated ones.

For me, with 16 XP-E Royal Blues on the same power supply, I had to adjust UP the voltage pot to MAX to run them at 1000 mA (I actually run them at 900) which got me to 52 V output, these DIM down to 10% or less with no problems. I have read and agree with posts that state that with Meanwells flicker on dimming is or at least can be driven by the voltage required to sustain the current setpoint drops below the supply limits and it flickers. So this makes sense and I am going to test this with new power supplies but I dont KNOW this is the case. IF I am correct in my assumptions, you can get around this by....

Do the math, look at the voltage v.s. current diagrams for the LEDs YOUR ordering and you can easily set yourself up for success. Its not that my set up does not work, its just not dimming as well as I want on two of my strings, so I am replacing them.

ALSO, ASK your vendor this specific question, I AM not an electrical engineer and this is just what I THINK is happening, and it makes sense but it easily could be some other thing, my vendor seems to have stated this can be a cause but I didn't ask I am getting this third hand.

The reason voltage drops is V=IR rearranged to get a set current is I=V/R since R is more or less fixed, you need to lower V to get less current, but I think this is a vast oversimplification as the voltage vs current plots are quite different from XP-G to XP-E so either R changes in some way or the system is more complex but at least this is where I am at in understanding how the this is affecting my dimming performance.

I can post back my new dimming results when I get the new drivers but it will be a little while.
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