Help me get the most outta these

[broncogearhead]

This is my first build. I'm looking to make a spotlight/floodlight for my truck. Gonna be used when camping etc.
I want it to wired to the truck. I'll have a cig lighter adapter or some other quick disconnect. I also have a few different housings to try to mount this in, I"ll post pictures of those later to get feedback as to what you guys think will be best.

What I have:
8 cree xre led's.
2 heat sinks. 2"x2" roughly.
two 1000ma buck pucks.
assorted lenses, mounts and heat sink epoxy.

I was thinking of mounting 4 led's on each heat sink.
Where I am a little unsure what to do is wiring them.
I was thinking of 4 led's wired in series on each buck puck. This ok?

Do I have enough heat sink?
What will give me the best power outta these?
I'd like to get the most I can outta this.
Any suggestions for a total led newbie?

 

[broncogearhead]

well i got bored and put 4 of these on one of the heat sinks i had. i ran them in series and used one of the buck pucks. i hooked it up to a 12v deep cycle battery i had and ran it for about an hour.
it never really got over room temp.
looks like i will need to play with lens and such to get the flood/throw i want.
i also still need to find a good way to mount and house the light/heat sink.
i still dont know if this is the best way to wire it, but it looks like it will work.
if i read the spec sheet on the buck puck right, i can run the rest of the led's on the one puck.

my question is, should i run all 8 leds on one puck, or 4 on each puck?
is there any loss of power, or brightness by running it one way or the other?

 

[Linger]

I want you to be careful with voltages, it'd be easy to a component working with a 12v power supply.

You didn't really describe your heatsink so it's hard to say. More is usually better. LED's most efficient cooler they are.
By 'most power' I presume you mean brightest (not longest run-time).
So while you could try and set up a boost configuration, IMHO it's not called for. 1000ma is really high current. Yes you could drive higher but the gains really drop off. Futhermore, the highest gains will come with the coolest tempuratures.

So be happy with your 1000ma buck-pucks. I believe your application is exactly appropriate for the driver.

What kind of xre's do you have? same batch or any variation? I'm asking because if the vf's differ between them it may be more helpful setting up into smaller strings (ie. not connecting all 8 like you just wrote, 4 may be too many)

Best,
L

 

[ahorton]

Unless you have amazingly low vf LEDs, your 12V supply is not enough. The LEDs probably light up, but I doubt you are getting a full 1 Amp through them. This would also explain why you could run 4 of them without much heat.


Try wiring just 2 of them up with the buckpuck and I suspect they'll be much brighter and start to heat up.

To wire 4 XR-Es in series and drive them with a buckpuck, I suggest a minimum supply voltage of 17V. Ie, 4 x 3.7V (for each LED) + 2V (for buckpuck).

 

[broncogearhead]

i'm using the cree xr-e q5.
these: http://ledsupply.com/creexre-w107.php

the heat sink measures: 61.00mm X 58.00mm X 24.00mm
this one:http://ledsupply.com/102-1489.php

i'm kinda stuck using the 12 volt source outta my truck. i'll be mounting the light to the tire carrier on the back of the truck. i guess you would call it a work/utility/flood/spot light.

i'll try just two of them wired to one puck. i'll report back how that works.

thanks for the input guys.:twothumbs

 

[Linger]

I just don't see enough thermal mass on that sink, the finning is nice but needs more mass.
My own barely educated 3 months of doing this opinion is that you should get a piece of flatstock (Homedepot) to thicken that up some.

 

[broncogearhead]

i can add 1/4 or even 1/2 inch aluminum flat stock to it.

problem i am having now, is finding a suitable housing for this.
i have gone down the electrical isle at lowes, looked at pvc and metal outlet, junction boxes etc. still did not see anything that would fit. or look decent.

any ideas?