LED replacement bulb for DeWalt 36v light

any suggestions on modding my 36v DeWalt light to an led? I don't exactly no what would need to be done in order to drive an led/array with that kind of voltage.

BTW the light is used for attic work (electrician) and would prefer to have it in the 100-200 lumen range to have all day runtime.

There is one mod that was done, here.

If you change the resistors around a bit it should work.

Good luck!
If you do it and post your results here, would be great.

Regards.

that would be a good mod Newuser01, but it seems like I might be cutting myself a bit short considering the power of a 36v Li-ion. I'm wondering, could the plastic housing handle the heat of the new crees? what kind of heat is involved compared to a 3w lux?
Seems there is plenty of room for a single high output emitter and proper heatsinking...

or is the problem in making a driver to run @ 36v nom.?

To my limited mod knowlage (which consist of reading on this forum, replacing bulbs and doing some dropins ie mag upgrade bulbs.) I would say the following.

Led's generally operate around 3.0 V. That is the reason behind all the resistors and pills and such. There is no such thing as 36 V LED.
In your question, you mentioned that it would be for attic work. I do the same kind of work and the light I use is STREAMLIGHT ProPolymer 4AA Luxeon LED (not lux) for a broad lighting and it would last almost a work day. I carry a set or 2 of extra Nimh AA's charged up and ready to go and it never let me down yet.

Check them out review, you can get them for about 25 bucks.

You will need some type of Heatsink that can transfer heat through metal to teh outside so your gonna mod the whole head. THen search buck converters and find out how to make one for 36-3 volts dc-dc in order to drive the light and it should work.

Thanks newuser01, I do understand that you can't run an led w/36v directly, I would need a dc/dc converter or a whole mess of resistors I guess... I just don't have much knowledge on the math involved. BTW the flex head is a great light for attic work because you can wrap it around trusses and point it at your work or use it like a table lamp. the major problem is if you drop it just a little the xenon lamp burns out.

thanks for the input 65535, I'm searching for the proper schematics for a 36-3 dc-dc circuit. I'm not sure though if I can pull off a machined aluminum head so I will probbably need to figure out a way to keep the plastic head cool or underdrive the cree to maintain a safe temp. over extended usage...heavy duty reflector and glass lens will be mandatory I suppose?

You could try using 6 6 volt Luxeon V led's or using 3 and getting some type of 2-1 dc-dc converter I think that is a question to ask in modding but also don't double post.

here are pics of the light, it seems the driver would fit in the housing
javascript:newProductWindow()

well available on the dewalt home page anyway

TechPro said:

I'm not sure though if I can pull off a machined aluminum head so I will probbably need to figure out a way to keep the plastic head cool or underdrive the cree to maintain a safe temp. over extended usage...heavy duty reflector and glass lens will be mandatory I suppose?

Click to expand...

Actually, I don't think you need the heavy duty reflector and glass lens. What you need is a chunk of aluminum to act as a heat sink for your LED or LEDs.

Plastic is a thermal insulator, which will trap heat inside the head, raising its interior temperature. The aluminum heat sink will spread heat away from the LED lowering its junction temperature somewhat.

But, the surrounding plastic will prevent heat from escaping the head at a decent rate. So, the aluminum will get hotter, as will the LED junction, until the light has been running for awhile and thermal equilibrium is reached.

I'm not aware of any plastic Luxeon LED lights that run at or greater than 3 Watts.

PT makes a 3 Watt Luxeon plastic headlamp, the Apex, but it has a finned metal heat sink molded into the head, with metal fins exposed outside the head. The plastic UK 4AA eLED Zoom runs its 3 Watt Luxeon LED at about 2 Watts, presumably to prevent overheating and failure of the LED.

drilling 1/16" holes in the back of the head to allow airflow over the internal metal reflector might let one use the reflector as a heatsink, these new cree emitters run relatively cool don't they?

after a lot of searching the big problem seems to be bucking 36v to 3 volts

If you run them at 350mA they run pretty cool and give good light.

would a pair of crees @350mA ea. run cooler than a single driven @700mA?
running two at the lower current would seem to run cooler to me and would be ran in parrallel to help with the power conversion problem, though, I still can't find suitable parts to drop even from 36v-6v...

TechPro said:

would a pair of crees @350mA ea. run cooler than a single driven @700mA?...I still can't find suitable parts to drop even from 36v-6v...

Click to expand...

Yes, they would probably run a little cooler because at the lower current the voltage drop across them would be lower, so the total power dissipated by the LEDs would be less.

Heat is the enemy. Remember that if you use a Cree LED, you will get nearly twice the light for about the same amount of heat. If you limit yourself to 3 Watts with a Cree, the light output would be equivalent to 6 Watts with Luxeons.

If you don't care about watertightness, you could drill holes through the plastic head which would allow some convective cooling.

You could also run thick, solid copper wire from the LED heatsink through the holes to an external heat sink.

Believe I've seen DC-DC converters that will work to drop the 36 V, but don't know where to find them off the top of my head. I'm certain that some CPFer does know, and will eventually point you to them. Ask over in the Mod forums.

thanks ringzero, a coppertubed heatpipe would be a great idea to get heat out of a plastic head while maintaining watertightnes, simular to what a gpu on a pc would use...hmm

TechPro said:

thanks ringzero, a coppertubed heatpipe would be a great idea to get heat out of a plastic head while maintaining watertightnes, simular to what a gpu on a pc would use...hmm

Click to expand...

Yeah, if you want to build something that elaborate with a heatpipe and external finned heatsink, you could drive your LEDs with righteous total power.

Maybe drive 4 Crees at 2 Watts apiece, for a Luxeon equivalent output of 16 Watts. That'd make for one BRIGHT worklight.