# Help in drive 92*Cree XRE P4 leds.



## Murilo (Mar 31, 2008)

Hi all 
My name is Murilo, im from Brazil and im trying to turn on at same time 92 Cree P4 leds.

Im was thinking about using 5 or 6 Lm3404HV but i dont know if its the best option, can someone give me some tips? ^^
In Lm3404Hv i was thinking in use a 73v x 6Ah supply to drive 3 rails with 18 leds and 2 rails with 19 leds, each one at 1A of current.

Someone have a better way to do this array?

http://img152.imageshack.us/my.php?image=dsc09400qe9.jpg
http://img143.imageshack.us/my.php?image=dsc09391mq7.jpg


Tks all 
Hugs
Murilo

PS: (sorry for my english :thumbsdow)


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## Mash (Mar 31, 2008)

Can you give us more info on the use?


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## Murilo (Apr 1, 2008)

Mash said:


> Can you give us more info on the use?




Sure, 

Im making a little led blade, in this form:
http://img521.imageshack.us/img521/91/dsc09431bw6.jpg

But i dont know which is the best way to drive then, maybe someone have a better idea then my (using lm3404hv)

the heatsink
http://img527.imageshack.us/img527/4931/heatsinkyq8.th.jpg

the blade with glue on heatsink
http://img262.imageshack.us/my.php?image=bladefullcb5.jpg

not necessary this wiring...
http://img527.imageshack.us/my.php?image=halfwiredbladerk7.jpg


can someone help me please? :$


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## Shaocaholica (Apr 3, 2008)

Are they all in series? Won't that be like 300V+ input? Thats pretty high.


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## dat2zip (Apr 3, 2008)

Murilo said:


> Hi all
> My name is Murilo, im from Brazil and im trying to turn on at same time 92 Cree P4 leds.
> 
> Im was thinking about using 5 or 6 Lm3404HV but i dont know if its the best option, can someone give me some tips? ^^
> ...



What is the supply range? You mention 73V. If that is a battery what is the full charge state and what is the fully discharged state voltage?

You might be better off with a linear regulator for some of the strings and the odd remainder a LM3404HV for the balance.

Another possibility if Vin doesn't vary too much is just a plain resistor.

Wayne


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## Murilo (Apr 3, 2008)

Shaocaholica said:


> Are they all in series? Won't that be like 300V+ input? Thats pretty high.



Not, on 5*lm3404hv im thinking in 3 lines with 18 leds in series and 2 lines with 19 leds in series, i will use exactly 92 leds, so maybe i need a 74v @6A suplly. 


Or can use 6*lm3404hv with 4 lines with 15 leds in series and 2 lines with 16 leds in series, in this configuration i need a ~65v @6/7A supply.


I was thinking in use computer power suplly with mod for higher output, i think i easy get about 20v 8A(i have 5 ps in my hands ), but the problem is the current of it.... i dont know how i can control it.. 

A friend in China found the lm3404hv for ~8 USD, and just for tell i buy a 300w AT power suplly for less then 8 USD, so idk what i can use 











Someone can help me? has some better idea?

Tks
Murilo


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## Mel_PL (Apr 3, 2008)

Murilo said:


> Hi all
> 
> Someone have a better way to do this array?
> 
> ...




Put off 2 LEDs, you got 90 pieces then.
Make 30 x 3 in series (each "three" with a resistor) fed from appropriate SLA. It will eat about 30 amps .

If you *must* use 92, the extra 2 can also be fed from the same SLA but with another resistor.

Just my idea.

-- M.


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## Murilo (Apr 3, 2008)

Mel_PL said:


> Put off 2 LEDs, you got 90 pieces then.
> Make 30 x 3 in series (each "three" with a resistor) fed from appropriate SLA. It will eat about 30 amps .
> 
> If you *must* use 92, the extra 2 can also be fed from the same SLA but with another resistor.
> ...




Tks for ur idea, and yes i need all 92 

From the power pc supply i can easy drain 13,[email protected] maybe 11,[email protected] too or try get 14,8 - [email protected], if i use to much resistors my final power will be too high i think but my fear is about the current on leds, that on the driver can be regullated to constant 1A thats why im think in lm3404.


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## Murilo (Apr 6, 2008)

Someone plx???


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## Data (Apr 7, 2008)

Murilo

Looks like a fun project. 

What does the bank of lights do? If you do not need to strictly regulate the light output then just direct drive the Cree XR-E emitters. They can take 2amps and still hang in there fine (see DB70 link below). If you design the power supply to within +-20% of one amp to each emitter that will be fine. The Cree emitter does not care about amps as much as heat. Just keep it cool. If you run the XR-E at around one amp and keep it cool, it will last for a long time.


my DB70 thread



Cheers
Dave


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## Murilo (Apr 7, 2008)

Data said:


> Murilo
> 
> Looks like a fun project.
> 
> ...



Tks for showing ur great job in this bank, my 92 leds will be drive to take light trough one lcd display for a diy projector, so, like u say, so if i can keep it cool i can drive it to 1,2A , so i think i will try use 2 of that pc power supply in 15v in parallel with high current diodes in output to give about 15v @25A

Do u have some other idea?

Tks!
Murilo
Brazil


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