DIY LEDs - The write-up

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As we're talking about this, how about mixing series and parallel in a single string? What I mean by this is if you have a string running at 1A and want to add a couple LEDs that have a max rating of 500 ma (say violets) can you wire them in parallel in a series string? and what would the Vf be for those LEDs?

for example
__________+C1-_____________+E1-
+A- +B-____________+D-____________+F- +G-
__________+C2-_____________+E2-

Ignore the _____________ that's just to keep things in the right place.
 
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Thank you guys. I understand now. I won't have any parallel strings or anything like that. Just 1 string of led's in series.
 
Yes, in theory you could do that - each little parallel chunk would be treated like an entire parallel-only circuit. So:

1) You'd need to experimentally verify that C1 and C2 were balanced, instead of just relying on datasheets to tell you so. This means putting a 1ohm resistor in series with each and checking current, or "binning" the LEDs individually.
2) You'd want to protect the LEDs from failure - this likely means putting a fuse in series with C1 and C2 that's rated above your target current in each but below twice that current.
3) The Vf "contributed" to the driver's load by C1 and C2 would simply be the Vf of C LEDs at the target current (500mA in your example).
 
LEDs

LEDs

der_wille_zur_macht said:
You can put any LEDs in any order you want on any string. The rule is this: The total Vf of each parallel string on the same driver MUST BE THE SAME.

So, assuming LED A drops 3.5v and LED B drops 3.2v (the blues and whites you are using) you could have the following strings on the same driver:
1) A, B, A, B
2) A, A, B, B
3) B, B, A, A

You CAN NOT have these three strings on the same driver with those LEDs:
1) A, A, A, A
2) B, B, B, B
3) A, A, B, B

If I am understanding you correctly, you want to make strings like:
1) RB,RB,CW,RB,RB,NW,RB,RB,OW
2) RB,OW,RB,NW,RB,RB,RB,CW,RB

Your two strings have the same counts of each LED so they'll have equal Vfs, so you will be perfectly fine. Keep in mind though that you still MUST test your LEDs/strings to ensure that they are all actually in spec, as Vf specifications are weak at best, and even small deviations can result in large changes in current.
Click to expand...

Yep willi, that`s how the strings would look :). Whew, ok, that`s cool, thanks guys :) Yes, i do plan on testing each LED in the strings and yes, i dident mention it but, i had planned on attempting to buy from specific bins for the whites, if i can that is. I had used the Vf values for these LEDs as they were stated on the Cree website, so that`s how i was able to determine i could use those 3 types of white because @ 700MA they were all 3.2Vf. If the binning becomes a huge hassle, then i`ll just go with a single white color, like NW. I really like the idea of being able to pick specific bin colors. That`s why i mentioned that program that lets you input 2-3 bin codes you like, and have the program give you a resulting bin code that closly resembles those 2-3 combined.
Wille the reason why i decided to mix the strings like that is because i really want that sunrise/set/lunar cycles ect., your controller can offer. Ex: the LEDS slowly increasing from one side(sunrise) and progressing as the day passes. Same with the lunar cycles, on a RT clock. I diden`t think you could do that if i seperated the colors in different strings.
 
S2minute said:
Wille the reason why i decided to mix the strings like that is because i really want that sunrise/set/lunar cycles ect., your controller can offer. Ex: the LEDS slowly increasing from one side(sunrise) and progressing as the day passes. Same with the lunar cycles, on a RT clock. I diden`t think you could do that if i seperated the colors in different strings.
Click to expand...

There doesn't have to be any specific relationship between colors of LEDs and how you control them. The "unit" via which you control LEDs is via which driver you attach them to - that is, all LEDs on a given driver are controlled together. However there's nothing that says you can't control several drivers together.

So if you were to put all blues on one driver and all whites on another, but you wanted to control them all the same, you could just connect them all to the same signal source.
 
Flazky said:
Does anyone know where I can get heatsinks in CANADA?
Click to expand...


Heatsink USA www.heatsinkusa.com ships to Canada. Their heatsinks often beat LEDs shipped the same day due to Canadian Customs.

As far as your dimming question simply take the Blue+ wire on your Royal Blue ELN Drivers and connect them together. Do this for the White- on the Royal Blue ELN Drivers.

Then use a Radio Shack Enercell skew 273-316 AC-DC Power Converter (Do Not Use The 12V Setting!) and connect the + output to the Blue wires and the - output to the white wires.

Then do the same for the White LED Drivers.

If your only using a single series of 12 XR-E LEDs do not forget to dial this driver down...Couple of you tube videos on how to do this.

The Enercells are $19.99 each

enercell-1.jpg
 
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S2minute said:
wow, that`s a bummer, i thought i could as long as the counts on each string was exactly the same and if each color group had the same VF.
Like ledA---ledA---ledA---ledB---ledB or any order, as long as the all of ledA was the same Vf and all of ledB Vf was the same on each string.
The way the strings were to be set up was like this:
RB XR-E will be driven @ 700MA and that`s 3.5Vf
White XP-G, even if they are 3 different types of white @700MA they are all 3.2Vf
So the strings: Ex: 1) RB,RB,CW,RB,RB,NW,RB,RB,OW (6 RB, 3 White)
2) RB,OW,RB,NW,RB,RB,RB,CW,RB ect. for 7 strings.
Each string would have the exact same count but, in different order on parallel strings. So now what is wrong?? I thought i had it finally:(
Click to expand...


A "different mix" means different "species of LEDs" not just a different order of the same LEDs. Least that's what I meant. Wille and Fish stated it and you seem to understand it. Go ahead!
 
The same mix requirement is because different types will have greatly different temperature coefficients. That would cause/force the various strings to all shift their Vf's differently as the rig warmed up, or a hot day verses a cold day would have one string hogging current.
 
bdare said:
HELP!

I'm looking for wire. On the site you guys suggested I can only buy 100ft of wire
http://www.bulkwire.com/wire-cable/stranded-hookup-wire-300v-ul-1007-1569.html

Anything wrong with this wire from fry's?
http://www.frys.com/search?search_t...ring=18+gauge+tinned+wire&minprice=&maxprice=
Click to expand...

i think what you are looking for are the following key words
stranded
tinned
600v
22awg


the link above has 18awg
you want something more like:
http://www.frys.com/product/1614660?site=sr:SEARCH:MAIN_RSLT_PG
 
bdare said:
HELP!

I'm looking for wire. On the site you guys suggested I can only buy 100ft of wire
http://www.bulkwire.com/wire-cable/stranded-hookup-wire-300v-ul-1007-1569.html

Anything wrong with this wire from fry's?
http://www.frys.com/search?search_t...ring=18+gauge+tinned+wire&minprice=&maxprice=
Click to expand...

For starters I don't see any wire on that Fry's page that's adequate. You want 24AWG NOT 16 or 18AWG.

Second, I can assure you those Fry's spools are not 100ft for $6. They look like only about 20ft. That makes them about 4X more expensive. But. That wire would be fine in the right gauge and may be just a drive down the street for you. You may only need about 20 feet.
 
Hey Kcress,

Interesting that I'd want 24 gauge. Isn't that smaller than 18? I also assumed I wanted the 18 gauge because that's what comes with the kits from rapidled. Also, the wire I showed you is rated to 600V which I think is higher than 300. I'm really not sure because I'm an electrical IDIOT!

Thanks,
Ben
 
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Why does everyone make there arrays in banks with spaces that cause light and dark 'strips'? eg; 6x4 space 6x4 space 6x4. Would it not be more natural to equispace the leds along the length and breadth of the tank, giving equal light throughout?
 
zooxanth said:
Why does everyone make there arrays in banks with spaces that cause light and dark 'strips'? eg; 6x4 space 6x4 space 6x4. Would it not be more natural to equispace the leds along the length and breadth of the tank, giving equal light throughout?
Click to expand...

cause that means you'll need bigger heatsinks which will add up a lot to the final cost, weight management and probably invest in more LEDs to cover the entire footprint and that is not needed. With adecaute optics and lamp height you can get a decent coverage over a tank
 
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