New LED DIY Build

[jthunder]

Ok, I've been reading on this board for the better part of 2 months trying to get an idea of what will work for me, and below is what I've come up with. Please have a look and let me know if I'm missing anything or overlooked something obvious.

I know that this isn't a lot of LEDs for the size of tank, but I'm going to start from this and grow it out as I need it. I can repurpose the driver to run just the 3 XM-L strips at 1.6a and get a second smaller 48v driver to power the RB strings.

Tank size/type:
240gallon tank, 72" x 24" x 26", this is going to be a mixed reef tank.

Electrical Plan:
1 48v driver with 6 parallel channels of 14 LEDs across the tank

For the voltage here is the story,
The XM-L's are 3vf and the XR-E's are 3.6vf at 800ma so I will move one of the XR-E's to the middle of the XM-L string. This will result in an approximate Vf of 45.6 and 46.8 (hopefully the difference of voltage will drive a proportionate amount current through the XM-Ls)

This gives me 13 LEDs per Royal Blue strip and 15 LEDs per the Cool White strip, and about a 4.5" gap between LEDs (with some gap on either side)
I plan on just using a regular power timer to turn the lights on and off and not adjusting the LED's or strips individually.


Equipment:
Heatsinks - 1" x 1/2" aluminum c-channel x6
Driver - Mean Well HLG-240-48A (48v 5.0a)
LEDs - 42x XM-L Cool White T6, 42x XR-E Royal Blue, 10x XR-E Cool White
18awg stranded wire for driver to bus
22awg stranded wire for bus to LED and between LED
3x 10 position bus
6x 1a fast-blow fuses
12x waterproof connectors
Plastic project box
solder crap

Basic Build Plan:
clean and prep aluminum channel
measure and mark spots for mounting stars
drill and tap holes
pre-tin stars
mount stars and wire (testing each for short to the heatsink with MM)
mount the heatsinks into the hood
Build the bus and connect the driver
Test!

 

[jthunder]

Surprise delivery today!

HLG-240-48A
42 XR-E Royal Blue
42 XM-L Cool White

I also picked up the C-channel and a few odds and ends. Now off to the electronics store tomorrow to pick up the wire, connectors, solder, etc.

 

[Jimmy54]

Sorry, wrong thread.

 

[smithj108]

(hopefully the difference of voltage will drive a proportionate amount current through the XM-Ls)

Hummm.... let us know how that works out.

 

[BluScrnOdeth]

Hey JT. I also used a 48V psu turned down to 46.5V, a 1amp fuse, and a 2.5ohm 5watt resistor. I have 14 RB and 14 CW LEDs on each array, rail, series, whatever you want to call it. I wouldnt run 6 strands off that one driver though. You only want to use about 80-90% max power off that meanwell to prevent early termination of your PSU. At most i would do 5. 800mA*6=4.8A = 96%

Going with 5, thats right at 80% and it gives you some play room for the imperfect LEDs fV and mA readings.

Did you really pay 100 bucks for that meanwell? IF not, where did ou get it. Total i paid about 50 with shipping for my setup but it's not constant current which from my understanding of reading a few things online, is about 10 bucks in parts.

Instructables has an interesting article on how to build a constant current device for about 3 bucks. I'll have to find it again.

 

[TheFishMan65]

(hopefully the difference of voltage will drive a proportionate amount current through the XM-Ls)

with

so I will move one of the XR-E's to the middle of the XM-L string

Is just asking to blow up an RB LED IMHO

I reall ythink you need 2 drivers one for each color.

 

[Jimmy54]

Or drive them all at 800 mA - but than agian - XR-E's will need 3.5 Vf and the XM-Ls something like 2.9Vf
Driving the XM-L's at 800 mA looks like a waste of money to me, they should at least be driven at 1500 mA to get some results.

So - 'repurpose the driver to run just the 3 XM-L strips at 1.6a and get a second smaller 48v driver to power the RB strings' - wouldn't be a bad idea at all

 

[lucidvtec]

vf voltage has to be the same....thats the minium voltage it takes to turn on the led....

the ma is the "brightness" on the led

also...deff dont' max out the PSU.....5 strings sounds bout right


correct me if i'm wrong

 

[TheFishMan65]

Vf does not have to be the same. The Vf will vary first by the amount of current applied. A certain Vf will be required to get the LEDs to come on. Then at a given current Vf will vary amoung different types of LEDs. And finally LEDs are created the same so even the same XP-E RB could have a different Vf and at the same current. All the charts and number are just an average value. I had XR-E vary 20% in voltage iwth the same current.

ma is the milliamps going through the LED. As the current goes up the LED get brighter, but the Vf has also increased just not as fast.

80% of the power supply is usually good. If it gets hot you are pushing it to hard.

 

[smithj108]

Quote:
Originally Posted by jthunder View Post
(hopefully the difference of voltage will drive a proportionate amount current through the XM-Ls)

Hummm.... let us know how that works out.

I don't mean for my comment to come across totally sarcastic. Part of me really wants to know... I've not had luck mixing LED's on the same string - others have. Then again I haven't messed with CREE's yet. I'm just having a problem wrapping my head around a string of all 3.6v devices, except one 3.0v device in the middle. LEDs are very current-natured so one can just consider voltage stats offered by the specs as a "ball-park" quantifier - as in, at 3.6v of electrical "pressure" one can expect 800ma of electrons to flow thru the device. The problem is that variances in the LED's themselves, and oh don't forget temperature make a huge difference in current passing capability. The best way to understand LED's electrically is the same way you understand the the non-light emitting one's (aka diodes), and that is they "short" in one direction. So the name of the game is to regulate the amount of current that shorts through them.

 

[TheFishMan65]

They also change over time - so I have been told. Which means balanced today may not be balanced tomorrow. Some one did a test of 2 strings of the same LEDs (same batch). IIRC one ended up with 80% of the current before the experiment was shu down. Make sure you use fuses and resistor (for measuring current) and IMHO you are asking for trouble mixing string types on the same driver.

 

[jthunder]

Ok, so this is what I have figured out right now. Running the driver at 800ma per string times the 6 strings = 4.8A, this is below the maximum rated power 5A of the driver.

Here is what I have planned for a total estimated voltage of 46.2 (also within the 51v maximum), these are based upon the average curves found within the cree spec sheets.

12 XR-E RB and 1 XM-L CW @800ma = 46.2
12 XR-E RB and 1 XM-L CW @800ma = 46.2
12 XR-E RB and 1 XM-L CW @800ma = 46.2
13 XM-L CW and 2 XR-E RB @800ma = 46.2
13 XM-L CW and 2 XR-E RB @800ma = 46.2
13 XM-L CW and 2 XR-E RB @800ma = 46.2

With the constant current and constant voltage this should be a safe setup as each string should be balanced. I understand I'm underdriving the XM-L's, but even at 800ma they put out about 300lm of light, as compared to the XR-E's that put out about 180lm at that current.

I will still be putting 1a fuses into each of the strings to prevent overloading the LEDs if a string blows, and also putting in .01 ohm resistors to measure actual current as they are running.

This setup also gives me the option at some point to upgrade the lighting simply by buying a 48v 3-4a driver for the three strings of XR-E's and using the HLG to drive three strings of XM-L's at close to 1.7a each.

Anyone have any suggestions on the type of quick connect to use for each of the strings? I was looking for a 2 wire molex connector, or some type of splash resistant type.

Thanks!

 

[Jimmy54]

300 lm @ 800mA when you have the $10,- XM-L U2 (2.9x0.8)x130) the U2 has 130lm/w
230 lm @ 800mA. when you have the $7,- XM-L T6 (2.9x0.8)x100) the T6 has 100lm/w (there are some 240lm LEDs for less than 3 bucks)

Another thing to consider;
39 XM-L x 300lm @ 800mA gives a total of 11700 lm,
20 XM-L at 1600mA will put out a total of 12000 lm when you have the XM-L U2.(18000 lumen from 18 XM-Ls)
The only thing left to do is find a way to spread them evenly and you've just saved yourself $190,-

EDIT:
BTW, I'm not sure about the constant voltage used in a DIY LED fixture like we want to "fabricate".
I thought it's the voltage that regulates the constant current and therefore needs to be a little flexible and not constant.
But like I said, I'm not quite sure how that works out in a setup like you're suggesting.

 

[jthunder]

So just to continue the voltage and current understanding, which I only really have a basic understanding of at this point.

With constant current power supplies, the total voltage would fluctuate with the current, so that if I hooked up a string of LEDs with a total forward voltage of 48v, the power supply would try to push all 5.0a through the string at the highest voltage it can put out. And the LEDs would continue to rise in voltage with the current until they blow.

With a constant voltage power supply, the total voltage is configurable and will not exceed the maximum setting, so with the same string of LEDs, the power supply will only supply the 48v required to power the string and then the current would be limited by the draw of the LEDs at that voltage.

With the HLG-240-48A, I can adjust the maximum limit for both current and voltage, so with the same string of LEDs, I can set the maximum voltage at just over the turn on point of the LEDs, and the maximum current to my liking, and neither will be exceeded regardless of the LED load. If an LED was removed (or blown) the current would only rise to the maximum set limit.

With this situation as long as I'm close to the total forward voltage of the string of LEDs, do I even need a resistor in each string? other than for measuring current. If so will a 1/4 watt 10 ohm resistor work?

Thanks

I know that I have a part of this correct just not sure how to explain it.

 

[Jimmy54]

So just to continue the voltage and current understanding, which I only really have a basic understanding of at this point.

With constant current power supplies, the total voltage would fluctuate with the current, so that if I hooked up a string of LEDs with a total forward voltage of 48v, the power supply would try to push all 5.0a through the string at the highest voltage it can put out. And the LEDs would continue to rise in voltage with the current until they blow.
1 string will blow right away with 5 amps, one big bright flash

With a constant voltage power supply, the total voltage is configurable and will not exceed the maximum setting, Right
so with the same string of LEDs, the power supply will only supply the 48v required to power the string and then the current would be limited by the draw of the LEDs at that voltage. the current regulates the voltage with the risk of a "thermal runaway" - as temperture rises current will rise and things get warmer and warmer etc. etc.

With the HLG-240-48A, I can adjust the maximum limit for both current and voltage, and also the area in which the CC operates.so with the same string of LEDs, I can set the maximum voltage at just over the turn on point of the LEDs, and the maximum current to my liking,the HLG has a minimum of 2.5 amp and 24 volts, so regardless what you want, 4 prallel strings of 7 LEDs when driven @ 725mA wil be the minimum
and neither will be exceeded regardless of the LED load. If an LED was removed (or blown) the current would only rise to the maximum set limit. the driver wil divide the "leftover current" among the rest of the strings, so more current for the remaining LEDs

With this situation as long as I'm close to the total forward voltage of the string of LEDs, do I even need a resistor in each string? nopeother than for measuring current.nope If so will a 1/4 watt 10 ohm resistor work?

Thanks

I know that I have a part of this correct just not sure how to explain it.I have try to explain it as good as I could, hope it makes sense

 

[jthunder]

Thanks Jimmy,

I think I have it figured now. I will be planning on hooking up all of the strings and setting the voltage and current to the minimum values. Then raising the voltage until the LEDs just light, then raising the current until I get to the desired level. I also plan on adding a 1a fast blow fuse to each of the strings just in case something doesn't work as planned.

I'll post pictures as I go. Lots of holes to drill+tap, solder pads and wires to tin...

 

[jthunder]

Well of course things didn't work out as planned.

After a marathon couple of days drilling, tapping, cutting, stripping, soldering, connecting, etc. I had all of the light strings ready to go and connected the HLG up to the house power supply. I had light.

Had because right after I plugged the meanwell in, the LEDs all came on, at least in some state. It looked really blue because the strings with just the XP-E Royal Blue were the brightest, and the XM-L Coolwhites were fairly dim. This is with both the voltage and current adjustments all the way down.

Based on my previous calculations I figured that if I could have the voltage somewhat balanced between the strings that a similar amount of current would be flowing through them. I have 6 strings that if I divide the minimum current of the 240-48a (2.5a) I should have about 416ma, and at the minimum voltage (44.8) I should be safely within the operating range for all the LEDs.

So like anyone that knows enough to be dangerous I increased the current POT slowly which brought the XM-Ls way up in output, perfect. Now I increased the voltage pot (not sure why I wanted to do this) and all of a sudden the XR-E strings went out! The XM-Ls stayed on though. I unplugged the array and turned the pots all the way down, then plugged back in, the XM-L's came back on, and I increased the current POT, then poof no more light! What did I do?!

I powered the array down thinking that I had just fried a lot of money in LEDs. I checked a couple of them with the multimeter and they were fine, then I checked across the fuses, and yup all blown.

So I understand that with the increased current and only the 3 strings of XM-Ls that the current would like exceed the 1a rating and blow the 3 remaining fuses, the part that I can't figure out is how the current would have ever got past 1a with all 6 strings running?

Any ideas?

 

[jthunder]

I plan on getting a bigger pack of fuses and maybe some in the 1.5a range so I have a bit more room to play with. Then I'm going to do some additional testing. This is my plan:

I'm going to buy a bunch of resisters and fuses so that I can take measurements across each string as I go.

Power up the whole array with the POTs turned to the minimum. I'm going to let the array run like this for an hour or so just so I know that it is stable. Then I'm going to raise the current POT slowly about half way up. Then if its still stable keep the current increasing until I'm at the max but within the operating ranges of the LEDs.

 

[TheFishMan65]

Do the RBs still work?

 

[jthunder]

Yup, all of the LEDs are still working, it just blew the fuses on the strings (and I didn't have enough replacements for them yet). I need to buy some resisters so that I can measure the current through each of the strings once they're on the lowest settings, then I can start figuring out what's going on from there. Any other pointers would be welcomed!

JT