I am not a guru about airflow, but I think that it’s a ratio thing. I think that convection does not work well when tube length is much greater than diameter. I think that it requires a high static pressure to move air through a long thin tube. Even if it’s 80mm in diameter, at 1.5m the ratio seems bad for airflow w/out high static pressure.
Not sure why you would need 5000 lumens, I have an uplighting floor lamp and it runs standard bulbs. It is meant to have a narrow beam directed spot light in it, about 60w. And the reflected light bounces around the room very well.
Point is it also works well with normal globes, plenty of light being cast from the standard bulb lumens (Im assuming under or around 1000).
You could probably underdrive these LEDs and get a nice room full of light. Heat neednt be a major issue.
Probably just a difference in expectations.
60w? I have two 200 or 300W halogen floor lamps pointing upwards, in 4mx5m living room, only when both are lit to the max, I would call it a very well lit room. It’s obviously quite subjective.
The AC current in Holland is 50hz ? ( all of North America has been at 60hz for as long as i can remember. either way the AC “buzz” flicker would be annoying.
We’re talking here about (I guess) 6V or 12V DC LED. I don’t see AC ever reaching the LED, hence AC frequency or voltage seem irrelevant. Just need an AC/DC adapter and driver to provide current.
DBSAR, 50Hz is normal outside of North America.
vex_zg, mention was made earlier of tapping into the 12v AC used to run some small halogen bulbs. It’s not a practical solution, but rectifying that current w/out enough smoothing would result in flicker.
When i want the room lit up enough to find a pin on the floor, I use the ceiling lights, a light design designed to cast light down. The up lamp is designed to create a room full of light, yet softer. They are rarely tall enough that when you walk past them you dont get an eyeful of light. But with low wattage its not bad at all. Its great for TV yet a still very well lit room. You could read by it if you wanted, but its not ideal for that purpose, however mine has a daughter light for that purpose.
But even still, these XH LEDs without being over driven provide how many lumens? Its well in excess of a 60w incan. Not everything must be bigger and brighter, lumens to the MAXXXX.
The XHP70’s currently cost around $20. I assume the price we’ll see once they arrive in quantity will be in the $8-12/ea range. That’s before $$$$ for support hardware.
If a person wants 60W equiv, why not purchase an existing product? Much cheaper that way, available now, and in a decent range of color temps.
You can already buy a 300 watt halogen version of an up light too, based on your above logic why not just buy that? Yes, heat, power costs, I offer you the same same logic as my first reponse.
60w wasnt the point, not driving to the point of needing active cooling etc was. These XH LEDs put out lots of light, without driving them hard was the point. That would be less $$$$ in your words, for ‘support hardware’.
I could make your argument for many lights that exist here, the equivalent thing could just be bought, but again, buying it isnt the point is it?
I’ve already pointed out that the XHP70 will not be able to keep up with a 300W halogen… and there is no way you’ll find an actively cooled floor lamp in my home. I’m sure that most folks here are not interested in a floor lamp with active cooling.
I’ve already made a specific proposal for passively cooling the XHP70.
Maybe you could state precisely what you’d hope to achieve with an underdriven XHP70 floor lamp? I feel very confused by what you are saying.
You have already pointed out? Thats some irony right there. It might help you if you go back and reread what it is youre responding too since you dont seem to retain it from post to post. Its just a tip that would certainly save me typing it twice. But Ill save you the trouble of scrolling up and finding the post and Ill quote it. If you can manage to read this without prejudice you should see plainly why that post of yours is obtuse.
I can only type it, I cant read it for you too. ‘Could probably’. I never said underdrive it, I said you could probably underdrive it and given its output still get very good light from a floor lamp, given a floor lamps design concept. Its not a workshop light, its not a bay light. There is no real need to create lots of heat.
As opposed to …
MOAR LUMENS
MOAR LUMENS
MOAR LUMENS
MOAR LUMENS
Sometimes you folks get carried away with absolute numbers, its like you have a complex … almost compensating.
Some very good discussion here, let me make a few points
The impetus for this light is plenty of raw lumens at very good efficiency and a good price.
The reason to use this LED is the likely better availability of 12V DC output power supplies.
If you want less lumens you can use a cheaper LED, heck if you have a power supply that will manage it use an XM-L(2) for 1000 lumens or buy a 60W (800 lumens) or 100W (1600 lumens) equivalent bulb which would do great for those applications at very low cost.
I would like fan free, its the weakest link but i want to be sure any heatsink can dissipate at least 150% of the LED wattage or the circuitry has thermal shutdown if it gets too hot (my preferred option)
I would like this product to be buildable by any BLFer so it would have a list of components, you buy them and assemble the light.
1) The power supply has to be certified (CSA/UL/CE etc), and one hopefully can be bought at a retail store or online, so if anyone knows specifics please post them so we can decide which one(s) are acceptable for this project.
2) The LED will become more common so once it is a list of sources and hopefully with tint options will be posted to the parts list.
3) The heatsink has to be able to dissipate the heat, likely CPU heatsinks will fit the bill but it has to be calculated or tested to shed the heat load.
4) A fan if required will have to have a high MTBF and a failsafe, if it stops working the light throttles back or shuts down.
5) The circuitry may be the hardest part, if off the shelf does not exist then it will need to be designed, ideally it has thermal protection, current regulation and modes. Programmable modes or even strobe (for disco parties) would be nice. The specifications of this are to be determined, if it will double the cost to get modes or other non critical features then they can be omitted.
6) The host would be a recommended one and easily available (an ikea one would be great because i believe many countries have one). Several possible hosts are nice to meet our varying needs, as long as it allows for proper heat shedding.
So what we need are suggestions, if you know of parts that will do any of these things please post them and i will investigate each one. Reliability, availability and cost effectiveness are how they will be judged, but post even expensive ones because if the cost differential gives much better performance its worth being checked out or added to the parts list as a premium option.
I find your post confrontational, inflammatory, etc. (I’m not joking. If we need to talk about it I’m available by PM.)
I pointed out my concerns about how much light this thing could generate in post #13. My point was entirely predicated on floor lamps which direct all their light upwards being halogen. In retrospect that may not have been entirely clear to everyone, although it’s clear that at least a few members were already on the same page. 
Are you telling us that you’d like to build accent lighting for your TV room with XHP70’s? When I suggested that you stick with a more sensible solution (such as existing 60W equiv LED bulbs) you responded with “I could make your argument for many lights that exist here, the equivalent thing could just be bought, but again, buying it isnt the point is it?”. I was trying to encourage you to reveal the specifics of what you want… not things like “You could probably” - hence my use of the words “state precisely”. I meant “state and endgame you would be interested in”. Rest assured that I read your posts several times to assure myself that you weren’t simply trolling. If I’d thought that was the case I’d not have responded, but it was a close call.
Probably a lot of this confusion/disagreement revolves tightly around the very different images that spring to mind when we think of floor lamps! You’ve got accent lights, reading lights, powerful up-lights, and others. In this context I think of powerful halogen up-lights when someone brings up an LED like the XHP70: it’s certainly no nightlight.
Please no arguing, this project is meant to build a light with lots of lumens that is safe, reasonable cost and doable by BLFer if they are interested. The discussion of its merits is not on the table, and i hope the design once completed can be adaptable, if you want to use a different host and make it a lamp/worklight/”lightbulb” thats great, if you want to use different LEDs, power supply and driver for less cost or less lumens and it meets your needs then thats great, if your needs can be met with an off the shelf bulb from a store with no need for fabrication then thats great too. I currently have about 10 60W equivalent LED bulbs around here and they work extremely well and i highly recommend them.
Bort, with your use of off the shelf “hosts” how are you envisioning the mounting system? The control system?
Single-mode is easy. Use an inexpensive CC/CV board coupled with a laptop power brick, printer power brick, or almost anything 12v+ and you’re done. eBay is full of CC/CV step down PSUs. Larger ones can handle more wattage, but for 1A operation this should suffice for $2 - DC-DC LM2596 LED Driver Step-down Adjustable CC/CV This gives you almost the ultimate flexibility for different genuine power bricks. What it doesn’t get you is modes, dimming, or a control system.
According to the Cree product characterization tool :
XHP70, P2 bin at 60ºC:
12.94V
2.4A
produces 3717 lumens @ 31.062W
Basically for this chip we need a power supply that can produce these requirements under load at the best efficiency available at reasonable cost, the host is one that someone has used and is widely available, the heatsink is tested to handle 35W of pure heat (with or without fan, to be determined), circuitry that provides the necessary current/voltage control and other features if feasible, and this entire light has to be able to be CSA or equivalent certified if it ever came up.
Once the light is proved and parts list posted, derivatives will be explored, using laptop power supplies most people have already, different hosts, reflectors, chips, etc.
If we try to make every light design creatable right now we will never get anything done since the possible permutations are endless.
Edit: Right now lets explore two drivers, one simple, one mode with thermal/fan control and one with modes, and other fancy options
Seriously, this is your tactic? You responded to my post, a post in which you distort and ascribed to me something I never said, and then you expect me to defend the things you ascribe to me? Yeah, not going to happen. I did however point out your error, but you choose to ignore that too and now suggest I have not addressed what you asked. Quite right, but youre asking from a skewed position. Im not going to defend that which I never said.
You found it confrontational because it was. If you dont want confrontation, do not put words in my mouth, then ignore when I try to show you thats what youve done, and then continue on your merry way ascribing to me things I never said. Ill leave aside your passive aggressive tactics too.
The best way to help this project is to take whichever area(s) you have expertise in and find and post components that will make the light work. I hope XHP70s will be available on noctigon/sinkpad/DTP star so that part should handle itself by the time the components are chosen. If your willing to build the prototype or to test it please also post that information.
We need specific suggestions for:
Power supply: certified that can provide under load 13V and 2.5A.
Heatsink: That can handle 35W with or without a fan. We need to be sure about this, so if someone has a way to test or lookup this information please let us know. How this will be connected to the host is a bit tricky but lets hope we can solve that by using a good host.
Driver: I’ve made some inquiries but if you can design or collaborate we need to know. If you know off the shelf that will meet the posted requirements please post that as well. Chinese drivers give me pause because of their questionable safety, but if proven to be certifiable then they are worthy of consideration.
Host: If you have ideas please post links, if you have used this host yourself thats even better
Fan: This is trickier since it has not been determined if the heatsink will need it, but high MTBF and reasonable cost are whats desired.
Didn’t someone create a (reading?) floor light using one of those cree cob lights (or similar)? I remember it had a HUGE cpu heatsink and it was a brown armchair in the final pic, but I cannot seem to find the thread. That would be a good starting point if it could be found.