# Can i use laptop charger to drive 6x Cree XTE in series ?



## gamezawy (Jul 2, 2013)

Hi all

Iam on my way to make a led lights for my fish tank

i have a spare laptop driver with 19.5 volts 4700 mA and this cree XTE runs with maximum 3.4 volts and 1500 mA

so can i connect 6x of this leds in a series and connect them directly to that Driver so every led will be taking about 3.25 volts 

so will it work and be safe ? and ofc this laptop driver is a constant voltage not constant current


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## foxtrot824 (Jul 3, 2013)

Hi, welcome to CPF! 

It is generally never a good idea to run LEDs off a constant voltage supply. By generally I mean never, the problem is that as the LED voltage changes as it warms up (usually goes down) so if you are trying to keep the voltage constant it will push more current through it that it will want to see resulting in a dead LED.

A simple driver will help you set up a safe and stable system. I'd recommend a buck driver, it just needs more power in than the string voltage. In your case I'd probably run two strings of 3 in series and run each to it's own driver. The reason I wouldn't recommend using all 6 in series is that at that current they will probably have a string voltage of about 19v and most buck drivers want a few volts extra to work with. I'd also recommend driving them a little less hard, this will help them run cooler and the decrease in output won't be too noticeable. I'd recommend looking at LEDsupply.com for driver and LEDs in small quantities. In my opinion a 1A driver per string would do the trick, something like this driver.

Good luck and post so pictures of the project when you finish.


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## gamezawy (Jul 3, 2013)

Thank you foxtrot824

But i had an experiment i did use a laptop charger with 19v and 4.7A to power up a 20x 3w chines Leds and it was doing fine i did a 4 rows of a series of 5 leds 

all i did i divided the 19V on 5 it gave me 3.8 so i used 5 leds in series and then i tested it , it only consumed about 700mA so i used another 3 rows 

by this i am not Arguing about constant voltage and i know it is better for leds to be run with constant current but it is not easy to find constant current drivers at my place and i will have to wait 20 days to buy one online


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## foxtrot824 (Jul 4, 2013)

Where are you located? There are other electronics distributors world wide such as cutter electronics that carry many driver options.


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## gamezawy (Jul 4, 2013)

I live in Egypt


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## foxtrot824 (Jul 5, 2013)

Rough times there, I hope you're safe. You might check out Future Electronics. They have distribution in many countries.


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## alpg88 (Jul 5, 2013)

sure you can. but i would add a resistor. 
all led strips are basicly 3 leds with resistor, and they are supposed to be connected to any power supply. not only CC supply.
i persoanaly hooked those strips to laptop power supply, not once. all work just fine. 
what you want to do is basicly same thing led strips are.


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## gamezawy (Jul 5, 2013)

i added a resistor it worked good i was very worried oh my god , then i tried without resistor it worked good and brighter all that done with a multimeter connected, the led draw only about 700mA my target is 1200mA this is the bad side of the constant voltage drivers you cant control anything , so i have to buy a Boost Converter driver something like that ( http://www.aliexpress.com/item/DC-P...nput-5-32V-Output-12-35V-Boost/545535803.html ) it convert any constant voltage driver to constant current driver


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## DIWdiver (Jul 5, 2013)

That driver should work well, but in very rare cases could overdrive the LEDs and the current limit might not work (because the LED string voltage is less than the input voltage). You could easily solve this by running a 7-LED (7S) string with it, or a 6S string with s series resistor.

Or you could run a 4S string and limiting resistor and no driver. You could run several of these on that supply. You could even run 5S and a resistor, but the regulation wouldn't be as good.


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## gamezawy (Jul 6, 2013)

here is my project pics 

i used a PC CPU heatsink 







attached like this 






LEDS mounted






final look attached heatsink together, leds mounted , leds soldered ,some lens mounted 






Laptop Driver now every led is taking 3.25 and that voltage made it consume 700 mA






testing 






My fish tank ^^






i hope you like it


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## DIWdiver (Jul 6, 2013)

Looks Gorgeous! I hope you enjoy it a long time.


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## satya (Mar 24, 2014)

gamezawy said:


> here is my project pics
> 
> My fish tank ^^
> i hope you like it



I too am planning to do the same for my fish tank, I brought 1W led and am looking for a suitable circuit. I have some DC adapters and laptop chargers at hand. I would definitely follow your path and build it.
I don't see any mention of resistor use to limit current, let me know how is your LED set up working. In my search for a circuit I found ( Instructables ) some constant current circuits which can be build for less than $4 and can be hooked up to a DC power supply ( Laptop charger !). I hope to get this done sooner. 
Please let me know how your LEDs are doing, if you have noticed any reduction in LED brightness. If yours are still doing great I would ditch constant current ckt and hook up LED to Laptop charger as you did.


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## Steve K (Mar 24, 2014)

Just a comment about the solder joints on the LED in the pictures you posted... it looks like the solder never got heated up properly and wetted the pad on the LED. As such, it's more likely to fail and the wire could disconnect from the pad. 

My guess is that the soldering took place after the LED was mounted to the heatsink, and the heatsink prevented the pad from getting warm enough to let the solder melt properly and for the flux to clean the surface. As a general rule, try to do the soldering before mounting the LED to the heatsink.


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