DIY LEDs - The write-up

[katchupoy]

George, why do you want 30 leds on one meanwell? it means that you can only turn it (30) on and off at the same time??? you dont have the luxury to maybe turn off 10 led at a time to make it like dusk dawn effect?

 

[katchupoy]

why use resistors? is this to safe guard the other strings if there is a blowout? 2 amps / 3 strings is 0.6 amps... on each string... then if one string fails... then it will become 1 amp each string which is still on the specs... then what if you put a 1amp fuse instead of a resistor?

[Edit]
so if on a regular meanwell driver you can drive 12 leds, then it should be 36 leds on this 2 amp driver correct? so that the voltage will across the leds will not change per string, only the current will change since 2 amps are being shared by 3 strings of 12?


sorry for stupid questions...

Fishman... i think he is referring to this tool...
http://led.linear1.org/led.wiz

 

[The Grim Reefer]

Did the test run on my fixture last night. Have LED's spaced out 3" apart with no optics. With the PAR sensor about 28" away it is giving me just under 110. Slightly less than I was hoping for but I can live with it.

 

[TheFishMan65]

katchupoy,

Thanks. That is designed for constant voltage. I don't remember all the arguments (maybe kcress will pop in soon) the general consensus is that that is not for us. And if you do do it that way then why use the meanwells?

 

[katchupoy]

Fishman, what do you mean by constant voltage? is the meanwell considered constant voltage?

Grim, did you intentionally plan not to use optics? how many inches above the water do you plan on yours? and will you be putting an acrylic or glass as splash screen?

 

[der_wille_zur_macht]

The Meanwell drivers and buckpucks and pretty much every other driver we use operates in a constant current mode when configured correctly. This is exactly what we want. If you put 30v worth of LEDs on a 48v ELN meanwell driver, it'll provide 30v at it's output. It regulates the voltage down to the correct level for the load you've connected, at the programmed drive current.

The use of resistors as current limiters is almost always only applicable when you have a constant voltage power supply, i.e. a common off the shelf 24v power supply, for instance.

 

[TheFishMan65]

The link you gave is assuming a constant voltage source. George then added a Meanwell driver to the constant voltage source. Something I would avoid.

 

[der_wille_zur_macht]

Exactly. Meanwell ELN drivers are not constant voltage drivers, so those formula don't really make sense to use.

 

[wfournier]

Would this be a good time to bring this diagram up again?

I actually just wired up an array using this design and will be testing it shortly. I have three strings of 5 XP-Es and two strings of 5 XP-Gs driven off of two ELN-60-24's so the XP-Gs get 1.25 A and the XP-Es get 833 mA.

 

[TheFishMan65]

NO! But you did. If you follow all the precautions you can do parallel or matrix (LEDs interconnected above). Typically what happens with these configuration is that if one goes out they all start to go. And that will start to happen after you leave on your 2 week SCUBA diving trip. They have been discussed here and/or in other threads.

 

[CJO]

ok im gonna give this a shot. but one issue, my tank has a foot print of 385 square inches BUT.. with my black eurobracing the exposed surface area of water is only 225 square inches. if i go buy the rule of 1,3 watt led per 10-20 sq" of surface area i can buy the 24 led kit and have all the power i need right?

Unless you only have corals directly underneath the opening, I would use the 385 square inch footprint for your calculations.

what should i do for optics? i was thinking because i will have more power than i need with the 24 leds that i could get away with the optics mostly used on an 18" deep tank when my tank is 24" deep ,,,or should i go with the recomended optics and just use real wide optics on the outtermost leds to try and get under the eurobrace????

The consensus seems to be that you should use optics for depth penetration. Use the recommended optics for your 24" of depth. I think if you use wider optics in the outermost LEDs, you will just be highlighting the eurobracing rather than getting under it, but that would be based on your LED placement.

CJ

 

[GEORGEDOPE]

Thanks for the response. The tool I was using is linked here.
http://led.linear1.org/led.wiz
What I want to do is use less drivers(Meanwells)
The plan I have will be 3 light boxes. Each one will have 30W and 30 RB LED's
This will be a total of 180 Leds over a 250 Gal tank. Dim 80"L X 26"W. I want only 2 Meanwells per Box. All the whites would be dimmable together and all the blues together. I plan on using a Profilx Light II for control. And what I've found out so far is that the Proflix can only handle 3 Meanwells wired in parallel. If I use fuses and one blows then all the fuses will blow. But with resisters if one sting goes out the rest of the strings will continue to light.
Does this make sense or is there another way to go with 180 Led's and 6 Meanwells.

 

[katchupoy]

George, is the driver you refer to dimmable? I did not see it on the specs?

@DWZM, thanks for the fix voltage explanation.

 

[GEORGEDOPE]

Yes it is. It's the only other Meanwell besides the ELN that is dimmable that I could find. But the HLG's go uo to 240W.
So a resister affects voltage and not current(amps) is that correct?
Or is current watts? One minute I think I got it and the next minute I'm lost again.

 

[Jay1982]

Ok, so... a few questions.

I tried, for the heck of it to solder an led while it was on the heatsink and sure enough I wasn't getting anywhere so I took the led off the heat sink and proceeded to try and solder. I came up with this:

I don't think this will be praised anytime soon as a good soldering job. Am I supposed to solder the pads I need and then later on heat the solder up again to add the wire? I tried doing both at the same time (this is how I thought I was supposed to do it) and it came out looking like this. Also, I imagine that golden gunk on the top part of the solder joint is bad news. Or is it "ok"?

Also, is there some small pad I could put between the heatsink and the starboard so that the heat doesn't transfer into the heatsink while I solder and once I'm done I can slide it out from under the leds? The reason why I am not liking the idea of taking them all off and transfering them is because I have everything set perfectly.

 

[Ra1n]

What about LED dimmer module does any one knows where they can be had for cheap without having to build one?

Will something like these work:
http://www.aircraftspruce.com/catalog/elpages/pwmDimmer.php

 

[The Grim Reefer]

Fishman, what do you mean by constant voltage? is the meanwell considered constant voltage?

Grim, did you intentionally plan not to use optics? how many inches above the water do you plan on yours? and will you be putting an acrylic or glass as splash screen?

Yep, no optics is the plan. Mine are mounted inside aluminum channels so I can put strips of acrylic over the opening.

Did the PAR reading with the fixture sitting on the tank which is about an inch lower than I plan. I get PAR in the 170's on the bottom. With water and the acrylic I figure PAR will be in the 140 range at the sand.

 

[The Grim Reefer]

Ok, so... a few questions.

I tried, for the heck of it to solder an led while it was on the heatsink and sure enough I wasn't getting anywhere so I took the led off the heat sink and proceeded to try and solder. I came up with this:

I don't think this will be praised anytime soon as a good soldering job. Am I supposed to solder the pads I need and then later on heat the solder up again to add the wire? I tried doing both at the same time (this is how I thought I was supposed to do it) and it came out looking like this. Also, I imagine that golden gunk on the top part of the solder joint is bad news. Or is it "ok"?

Also, is there some small pad I could put between the heatsink and the starboard so that the heat doesn't transfer into the heatsink while I solder and once I'm done I can slide it out from under the leds? The reason why I am not liking the idea of taking them all off and transfering them is because I have everything set perfectly.

Solder the pads and the wire then melt them together. If you have a piece of ceramic tile laying about that would make a great insulator between the star and heat sink

 

[tahiriqbal]

What you could do, get a small adjustable wrench and fasten your LED star and place it where you need your star to be mounted and then solder. You could easily unfasten your wrench and move on to the next LED hence not having spider web all over

 

[hllywd]

Ok, so... a few questions.

I tried, for the heck of it to solder an led while it was on the heatsink and sure enough I wasn't getting anywhere so I took the led off the heat sink and proceeded to try and solder. I came up with this:

Twist the stripped ends of the wire then tin it, that is, heat the wire then touch the solder to the wire. It doesn't look like yours is. Do the same to the pad you intend to solder the wire to. If you can't do it with the stars attached to the heatsink you need a hotter iron. I have the el Cheapo Weller WLC100 and it will tin pads on the heatsink within a couple seconds. It's probably easiest to cut and prep a batch of wires, and have the pads all tinned before you begin to assemble anything. Always heat the part with the iron then touch the solder to the part to melt it. Once you're ready, hold a tinned wire to a tinned pad and touch the tip of the soldering iron in such a way as to melt the two pieces together. IMO, you're pic shows untwisted strands, too much solder, and not enough heat.

BTW the "golden goo" is the rosin from your solder, another thing that says your iron isn't hot enough. How heavy is the solder you're using? I like the really fine stuff... that could be part of your problem too.

HTH
Tim