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Discussion Starter · #1 ·
Hi folks,

Having nearly come a cropper on the cycle home the last 2 nights from not being able to see things inthe dark, i have been inspired by achesalot's design to make my own luxeon based front light.

Now, i haven't ever seen these little babies in the flesh, but can people confirm / deny whether a luxeon + a lens / reflector would fit into a 20mm high slot / space.

My plan is to have: 4 luxeon 3W LEDs running in 2 pairs. Each pair running through its own buckpuck controller. All 4 lights will be in a horizontal line.



Only to the second question, is it possible to over-cool them? The setup i have in mind is based on fitting the lights plus controllers into a 70mm by 100mm base plate area. This happens happens to be the same size as a pentium 3 heat sink i have lying o the desk . . . the fins are 30mm high over the whole surface. So, as well as being rediculously large looking :D would the cooling effect become too large?


cheers,

Donald
 

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Donald,

No you can't over cool a Luxeon. The cooler the better! :D

At this stage I would strongly suggest that you have a good read of the data sheets at www.lumileds.com, particularly those in regards to Thermal management and Lumen maintenance. The thermal management of Luxeons is critical to a long life and high output.

The datasheet for the three-watt Luxeons will have a mechanical drawing with all the measurements you need to know. It will obviously depend on your optic / reflector choice as to how tall it will all sit.

Your paired array with two buck pucks sounds like a solid solution. Have you considered what optics / reflectors you will be using yet??

Cheers, Dave.
 

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donboyfisher said:
Now, i haven't ever seen these little babies in the flesh, but can people confirm / deny whether a luxeon + a lens / reflector would fit into a 20mm high slot / space.
Specs on the 20mm IMS reflector shows that it will extend about 18.5mm above the surface the Luxeon is mounted to (whether you use stars or emitters). If you find yourself having to trim the length of the reflectors, trim the front, not the base of the reflector like I did! Most lenses+holders are shorter than the reflectors.

http://www.quickar.com/ims.pdf (good place to purchase them too).
Much more info on the Luxeons at http://lumileds.com

donboyfisher said:
Only to the second question, is it possible to over-cool them?
Not possible to overcool. But I find that riding in the generally cool night air (avg 10mph) does most of the cooling for you. I only nightride in the winter (50-70F temps here in FL), due to the shorter daylight hours. My TriLux light remains cool to the touch while riding. Since the entire case is aluminum, it alone serves as a pretty good heat as long as air is moving over the case. But as my friend Dave said, "I think the fins look cool and are great for cutting spider webs." :) Seriously, as long as you're moving, cooling will not be a problem... but you should plan for the possibillty that you might stop for a while and need your light on full power to look for something or fix a flat... in that case some heatsinking comes in handy.

I'm thinking about leaving off the heatsink fins on the Dual Lux V I'm currently building since I think I've improved the capability of the case to act as a heatsink.

BTW. Glad I (my light) could provide some inspiration! Go for it!
 

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Seriously, as long as you're moving, cooling will not be a problem... but you should plan for the possibility that you might stop for a while and need your light on full power to look for something or fix a flat... in that case some heatsinking comes in handy.
Sorry but I have to disagree there. No amount of cool air will help you if your heatsink is a poor design. Again the datasheets are a good read here.

Heat sink design isn't so much about physical mass or size, but more surface area, and the ability for the heatsink to dissipate the heat generated by the Luxeons.

Dave.
 

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I didn't mean to imply that heatsinking is not required at all.

Just talking from experience. I've seen some guys do silly things like mount a bunch of Luxeons on a massive heatsink, strap it to their handlebar and call it a bike light. To top it off, they put the heatsink to the rear, where it gets little airflow. Obviously you can't glue 4 Lux IIIs to a piece of wood or plastic and expect them not to fry. Dave's right though... check out the Lumiled docs on thermal management. Aluminum and copper make good heatsink materials. They do mention things like ambient temperature and air flow across heatsink surface area as factors in thermal management. And you can see in their diagrams, airflow allows reduced heatsink surface area.

Maybe I assume a reasonable amount of common sense here?
So let me rephrase: "wind chill factor is your friend"
 

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Discussion Starter · #7 · (Edited)
thanks for the replies so far chaps.

i'll go and have a read of the luxeon information in the link.

My plan was to use the 18° reflectors from quickar. I was looking at the PDF and it does look like it'll just fit.

To give you an idea of my current plan, here is diagram of the idea i have at the moment. The luxeons will mount directly onto a piece of alu c-section and that c-seciton will join directly onto the base of the heatsink. The heatsink will actually form the main structural component of the light onto which the rest of the parts will hang.

The components are roughly to scale with each other, so as you can see, the heatsink is a bit of a whopper!





one thing i haven't considered to much yet is the handlebar mount - are there any good links on generic mounts / ideas?

thanks,m
 

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Discussion Starter · #9 ·
Dave will be happy - dont worry.

the heat sink top has rows of spikes. in the 1st pic, you are seeing a single row of the spikes runing from front to back.

if you could overlay the heatsink on the 2nd pic, the rows would run vertically so the air flow is as good as possible.

its early days yet, but over the weekend i'll try and cut the parts of alu together to form a basic shape and take some pictures.
 

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Sounds good. Keep us informed of your progress and don't hesitate to ask any questions. 4 Lux IIIs will put off a good deal of light! What bin Lux IIIs are you using?

BTW, I'm waiting on another Lux V, 2 reflectors, and a Downboy driver to finish my 2xLuxV light ....hopefully it will come tommorow.
 

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Good stuff guys. Your plan looks great Donald. :D

Maybe I went a little over the top preaching about reading datasheets.... :(

I just wanted to make sure that you didn't destroy 4 nice 3 watt Luxeons!! :D

If anything you could probably run a slightly deeper C-section piece (the one that the Luxeons mount to), and use a slightly smaller heatsink (as in height). It's always hard to tell from drawings, but I'm sure that’s way more then ample cooling.

I guess you’ll mount a piece of Perspex or similar over the front to keep the dirt and water out??

If you’re careful, you could use this to hold your reflectors against the Luxeons instead of bonding them. It would make future modifications with different optics / reflectors a little easier too.

Keep us posted!

Dave.
 

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Heatsinks are aluminum....

Bikes are aluminum....hmmm.

Im thinking an intergrated 3x3w light/stem sytem...And using the most advanced CAD software available, heres what it might look like...

The light unit would attach to the stem plate via interlocking...umm...thingies. Kind of a tounge and groove system. A quick release skewer would hold the light at the desired angle. To adjust the angle, flip the QR, set angle, tighten QR. To remove the light unit, remove the skewer, and the light unit slides out. The small diagram shows as if you were standing over bike, looking down at the stem. The big diagram is a rough side view with handlebar cut away, and only one "tounge" is shown on the stem plate.

Of course, this is far beyond my capibilities. But if someone had machining skills....
 

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Hi Chris, there are a few of us who are either members or lurkers at CPF. Definitely a great resource!!

ICanDigIt - You're not trying to out class Hope are you?! :D

Remember that the whole point of a heat sink is to dissipate heat. An increase in size and mass isn't always better.

I’m not saying that it wouldn’t work just fine, but you would be better off making a smaller heat sink that has more surface area exposed to the air, then making one with more bulk.

Cheers, Dave.
 
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