Experimental build_Cree_XPG_R5

[Microa]

Target: I am planning to build a XML head lamp. Since i am living in the subtropical area.
The temperature is as high as 33C in the summer time. I made this experimental build to collect data for the next XML head lamp.
Emitter: Cree XPG R5
MCPCB: 20mm star modified to 9mm round
Driver: home made AX2002 buck driver, 700mA driving current setting.
Housing:30mmx30mmx15mm finned heatsink plus 39mmO.D.x22mmI.D.x18mm 6061 Al ring about 12SQ.IN. total surface area.
Optic: 20mm 45 degree flood lens
Front len: 2.5mm thick acrylic sheet
In line switch: to be confirmed in next build
Battery pack: home made Sanyo 18500 x 2, 2S1P with balancer protection PCB
Charger: home made Microchip MCP73864 linear li-ion battery charger
Result: At 18C ambient temperature, the temperature of the heatsink at the point under the LED held stable at 45C in still air.
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[Th232]

Looking nice, always good to see how much of it is home made.

Just wondering, how efficient is the diver?

 

[Microa]

Hi Th232, The data sheet said 91% efficiency. There was an efficiency chart on page 5 #138 http://www.candlepowerforums.com/vb...ing-for-driver-(updated-kennan-driver-)/page5

 

[Th232]

Looks good, but have you measured the efficiency yourself?

I ask because in my (admittedly limited) experience in making drivers myself, reaching the efficiency that the manufacturer claims has been a very difficult task. On my last attempt I fell about 10% short of what the datasheet said.

 

[Microa]

I didn't measure the efficiency myself. I lack of equipments to do so. May be I can measure by a cheap multimeter for reference though it is not accurate to measure high frequency pulse. But the result is always useless.

 

[Microa]

I did 3 cycles of time duration test. The head lamp operates 4 hours and 5 minutes per charge. The batteries are rated minimum 1620mAh and the driver draws 360mA from the batteries.

 

[Th232]

Sounds good. I presume that current draw was measured at the start of the run?

 

[Microa]

The current draw was measured at the mid-point of the run. I don't want the fresh charged batteries over stated the reading.

 

[Th232]

Nice, assuming your batteries were around 7.4V total at that point (protection PCB cutoff at ~3.2V ea) efficiency would be around 84% at that point, give or take a bit.

Looking forward to seeing the XM-L version!

 

[Microa]

The temperature rised to 54C at 24C ambeint temperature yesterday. I should increase the surface area of the housing for the next build.

 

[Th232]

I'm unsure if it's worth the effort for you, but if you want to run some simulations on passive heatsinks you might want to try a neat program called NatSink. The site seems to have shut down, but the Wayback Machine still has a copy archived here:

http://replay.waybackmachine.org/20090505175352/http://www.frigprim.com/frigus_natsink.html

 

[Microa]

Thanks, I will download to have a trial.

 

[motomaniac]

Looks great. Will this work on a dirtbike will a dedicated 35w lighting coil???

 

[Microa]

Do you mean whether this work on a bicycle dynamo? Suppose it can. Driving one LED, AX2002 requires 6V Vin. The dynamo output is AC voltage. requires diode and capacitor to convert into DC voltage and smooth out the ripples. The LED can be driven to 1.3A (Data sheet listed maximum is 1.5A) with adequate cooling.