LED Fixture Build --Kcress--

One more question for tonight, and you probably covered it already.

I did a search at radioshack for a 1 ohm 2 or 3 watt resistor and all that the search is finding me is 1.5k ohm 1/2 watt 5% resistor. The search grinds all the way down to a 10 ohm 1 watt 5%.

And google is finding me alot of 1K ohm resistors.

I need to make a trip down there. Or am I just wasting my time and should order online. Thanks again man!
 
Thanks again man, you're awesome. At Digi-key the resistor's are backordered until May, but thats ok.
 
Cool thanks for all the help. Now lets get back on track how's this build doing? Been a bit since your last update.
 
Thanks Kcress for going into detail on the parallel strings. Finally I see some pictures so I know what I'm doing.

Kcress- Does that driver you use have dimming capability?
I am planning a 200led build with cree leds and I plan to do parallel strings to cut down on drivers and the mw 60-48d was the driver I was going to use. Can I wire it up the same way you did wit 24 leds on each driver to get approx. 700ma per string after the testing you explained?
 
dude man this is awesome! now just hook up yhour microcontrollers ADC to the resistors and monitor the current 24/7 :smokin:
 
zero26 said:
Cool thanks for all the help. Now lets get back on track how's this build doing? Been a bit since your last update.
Click to expand...

Yeah yeah... :hmm4:

I am snarled in doing my corporate taxes... They're due today so I've been hammering on them. After I get them in I'll be back on track.

I'm also having trouble figuring out what to house the fixture in. Maybe yoos guys can help.

I was thinking acrylic, like maybe black. But dang! All you have to do is look at it and it gets fingerprints and scratches all over it.

I originally was going to surround it with some nice wood. But that requires some sort of finish...

Opinions? Ideas?

chadfarmer said:
thanks all for all the info going to get mine going
Click to expand...

:thumbsup:

bobbyrocco said:
Thanks Kcress for going into detail on the parallel strings. Finally I see some pictures so I know what I'm doing.

Kcress- Does that driver you use have dimming capability?
I am planning a 200led build with cree leds and I plan to do parallel strings to cut down on drivers and the mw 60-48d was the driver I was going to use. Can I wire it up the same way you did wit 24 leds on each driver to get approx. 700ma per string after the testing you explained?
Click to expand...

No dimming. That fixture is a test bed for that style heatsink and won't be anything permanent. So I wasn't needing dimming or the total hassle MW makes it just for a test.

Yes you can use a ELN60-48 instead. You might want to go with the 1 ohm resistors instead so you don't have to think about it when measuring the string current.

Skeptic_07 said:
dude man this is awesome! now just hook up yhour microcontrollers ADC to the resistors and monitor the current 24/7 :smokin:
Click to expand...

Thanks Skep! LOL That would be pretty boring if the current driver is any good at all.
 
Hey Kress, I am having a little problem with my build so thought I would post here incase no one sees it on the main LEd build thread :). When you did the probing of the Led on the pad and on the heatsink, although you have no problems I am experiencing it. So I was curious as to what is the next thing I need to do in order to fix it? Say you did have stray voltage when you test, what is the next step if that is the case? Thanks.
 
Hey Kcress,

Thank you so much for all the help that you have given others in your threads as well as others. I just finished my first 2 string parallel that will be for my frag tank (2 more on the way for my DT). Most of the information that I got was from reading posts from you and Fishman. Very helpful!

I have a quick question regarding the string match. My strings are relatively even matched after I isolated one underperforming LED in one of my strings. My meanwell 60-48d puts out a scorching 1.9A (This cant be normal!). Running at 9v and the pot turned full open (clockwise), My present strings are about (going from memory at the moment):

Across the resistor
String1: 980
String2: 930

Would it be worth running the strings for a while and see what settles? Will I cause damage if i do so?
 
As long as the LEDs are rated for the current, I don't recall if the RB are, you won't hurt the LEDs. The ELN is another story. If you run an electrical device out of its specified range you always risk damaging it. The conservative thing to do would be turn it all down to something more reasonable like 1.4A. The interesting thing to do would be leave it run where you're at. LOL Just realize it could blow any time. Try to keep it cool. Maybe put a fan on the ELN.
 
Cool, but do you think that they are balanced enough, or is that too much of a gap?

kcress said:
As long as the LEDs are rated for the current, I don't recall if the RB are, you won't hurt the LEDs. The ELN is another story. If you run an electrical device out of its specified range you always risk damaging it. The conservative thing to do would be turn it all down to something more reasonable like 1.4A. The interesting thing to do would be leave it run where you're at. LOL Just realize it could blow any time. Try to keep it cool. Maybe put a fan on the ELN.
Click to expand...
 
It's right on my arbitrary guesstimate of what 'unbalanced' would be. I'd probably leave it but monitor it. If it shifts further I'd probably consider balancing.
 
Alright then. I will check it every few weeks and see if things settle or get worse. Thanks for the feedback.

kcress said:
It's right on my arbitrary guesstimate of what 'unbalanced' would be. I'd probably leave it but monitor it. If it shifts further I'd probably consider balancing.
Click to expand...
 
Nope. I haven't 'housed' it because I'm going to incorporate it into an ATS I haven't built yet. I have it sitting on the surround around a 55g lighting one half of it. It's really nice compared to the *)&%$# CFLs I replaced with it.
 
I have one of the marineland reef capable fixtures that I traded frags to the fish store for and I am still amazed how well it grows coral. LED is the future, I just hope they last as long as advertised.
 
Commercial ones are pushed to the limits to make them cheap-to-build so I'd not expect more than a few years out of a commercial unit. Still beats buying replacement bulbs.
 
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