leds wired in parallel and in series

dexter9

Active member
Joined
Dec 19, 2011
Messages
27
Hello, i have a question about a setup that i have in my mind.
I allready have laying around a 5 led R2 module with a broken driver, a xml led and a buck driver for xmls
parts:
http://www.dealextreme.com/p/5-cree...drop-in-led-module-52-7mm-42mm-8-4v-max-35242
http://www.dealextreme.com/p/6-18v-3000ma-3-mode-circuit-board-for-xm-lt60-emitters-57779

and i wanted to make something out of them, i was thinking of replacing the R2 middle led with the xml and wire it in series with [the rest of the R2 in paralel] and power them all from that xml driver, or have 2xml and 3 R2

is this ok?
 

AnAppleSnail

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Joined
Aug 21, 2009
Messages
4,200
Location
South Hill, VA
First of all, 'R2' is nothing but a brightness bin. Which LED is it? The picture at DX shows XP-E, which are rated at 1 amp each. The XML has a lower Vf and a higher current rating.

Putting LED in parallel requires matched forward voltages. There isn't a way to easily manage this with 5 XR-E and 1 XML. You won't get good performance, but that driver is probably going to only work with all the LEDs in parallel. Doing this with 1XML and 4 XR-E will make the XM-L brightest, possibly overdriving it depending on the Vf of each LED.
 

DIWdiver

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Jan 27, 2010
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2,689
Location
Connecticut, USA
That setup should work okay, since you are going to put the XM-L in series with the group of XR-Es. The XM-L should see about 3A, and the group of XR-Es will see the same current, whatever it actually is. The XR-Es are probably close in voltage, since all the LEDs on a single board very likely came from the same reel. They won't current share perfectly though, so it's good that you would be underdriving them at nominally 0.75A each. It won't matter that the XM-L voltage is lower than the XR-E group voltage, since they are in series, not parallel.

You'll need to have at least 8V, maybe more at the input to get the full 3A output, but that shouldn't be a problem.

If you did 2xml and 3xre, the xre's might not like it very well, as they would nominally be at max current, and any current imbalance would push one of them over 1A. You might get away with it, or you might blow all the xre's in a flash (but more likely the failed one would short, protecting the others). The other thing is you would be pushing the power dissipation way higher than the board was designed for, and that could be a problem too unless you have better than average cooling. Plus you'd need 11+ volts to run it.

On the other hand, the current is likely to be well under 3A. You might want to hook it up to an xml and measure it, then assuming it's not OVER 3A, try 2xml in series. The current might be lower, and will probably change with input voltage, so measure at both min and max battery voltage.
 

beekeeper5

Well-known member
Joined
Jul 18, 2010
Messages
161
I have the DX 5 * R2 Cree dropin. One of the LED is dead but I can't seem to get it out. It's stuck in there with some white glue(?). Any ideas on how to remove it?

Also, the DX 5 * R2 Cree dropin driver died (again!). Is it me or am I just having bad luck with the driver?
 

dexter9

Active member
Joined
Dec 19, 2011
Messages
27
it's easy to remove the leds, i did it. (same problem)
hold the led with a small pair of pliers(you can find a good grip around the led-aluminium part) and then try to rotate the led, it will come of very easy

AND DON'T WASTE MONEY ON DX AGAIN.
 
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