SIS desk lamp modding with 2x 50W Epistar LEDs

Hi!

In the meantime, I made my desklamps some more sophisticated.
Old thread here:

http://www.candlepowerforums.com/vb...with-awesome-brightness&p=3945157#post3945157

I decided to use these 50W LEDs instead of the LED strips.

http://www.wayjun.com/index.php?main_page=product_info&products_id=856

I chose the cold white version, which works out excellent as a work light.
I used the same driver as before, but now with a relais, as the current pulse at the beginning always burned out my switches.
I used Arctic cooling MX2 thermal paste. The LEDs are fixed by stainless steel bicycle spokes which are bent in a way that they constantly press the LEDs down. The surface of the aluminium was smoothed with 1000grit paper and slightly polished after that.










Before:



After:



Photo album:

http://imgur.com/a/lPyAo#2

http://imgur.com/a/voKaM#1

I cut a class panel to sit in the place where the aluminium sheet for the LED strips was located before.

I really like this mod much better! The light is brighter again, the lamp head provides good heatsinking, and these LEDs have a higher CRI.

two questions:

1. how hot does the light get? It doesn't appear to have much surface area to use to transfer the energy to the air.

2. were the spokes DT or Sapim?

Be warned, I suspect those Epistar chips will fade out rather quickly and have a short lifetime. Just based on my bad experience with one.

Another idea, if someone is planning to make another lamp like this, is to incorporate a small red LED chip in there for "high CRI" LED light. Online sellers offer a 10W red LED chip, but that would make it more complicated because the voltage is different so there would have to be two separate power supplies.

Julian Holtz said:

I decided to use these 50W LEDs instead of the LED strips.

http://www.wayjun.com/index.php?main_page=product_info&products_id=856

Click to expand...

9500 lumens for a desklamp, really? Maybe a basketball court.
Or perhaps stick this out your 2nd floor window for a driveway light.
I LOVE the sturdiness and price of this lamp tho!

Steve K said:

two questions:

how hot does the light get? It doesn't appear to have much surface area to use to transfer the energy to the air.

Click to expand...

I was wondering that, also. Maybe put some SERIOUSLY BIG fins on the top of that lamp. At 100 watts of LED power, maybe that nice flat surface could double as a frying pan. SERIOUSLY tho, I'd monitor the temp, and cut the current to regulate. OR, as I've always wanted to do, is water cool. Julian could run a couple of 1/8 in swamp cooler hoses to circulate water to the top of lamp, and have an enclosed chamber heat sink up there, or leave it open, with a tiny wall and have a few tiny rubber ducks floating above your desk, in a pond to keep those LEDs COOL.

Weight should not be a problem if the power supplies are moved out of the head to compensate.

Anders Hoveland said:

Be warned, I suspect those Epistar chips will fade out rather quickly and have a short lifetime. Just based on my bad experience with one.

Click to expand...

Did it have incredible heat sink attached? My initial thinking of using 50W chips, is 'holy crap, gynasium ceiling lighting. Better keep them doggies COOL!'

Brian

Hi!

As I happen to have my IR thermometer right beside me: Peak is 57°C right under the handle, at 25°C ambient temperature. Keep in mind that I seriousely underdrive those LEDs with just 670mA current, so I have less than 40W from both combined, and around 3000 lumens "only." Maybe this is the reason why the LEDs cope with the high temperature happily and I did not see any degradation at all yet, and I am using this light a lot. I just got my engineering technicans degree, and this involved a lot of studying on my desk.
The critical component here seems to be the cheap chinese driver, which I operate out of spec by a huge margin. After switching off the light for some minutes, I still measured 60°C on it's case. It has given me some random flickers over the last weeks...
Should it fail, and this would be alright in this environment, I will try my luck with a Meanwell HLP-40H-54.

Julian Holtz said:

I seriousely underdrive those LEDs with just 670mA current, so I have less than 40W from both combined, and around 3000 lumens "only." Maybe this is the reason why the LEDs cope with the high temperature happily and I did not see any degradation at all yet,

Click to expand...

Oh, underdriven, my appologies then. That's how the Philips L-Prize got such great lumens/watt. They are driving 2 watt LEDs at 1/2W each (i think that's what I read) Don't you want to try the water cooling pond though? (On top of the lamp)
Brian

I want to keep it solid-state, so no fluids for me

But right after my last posting, the power supply quit working in larger intervals. So it is time for replacement.
The Meanwell HLP-40H-54 is nowhere to be found for a decent prize, so I'm going to install two pieces LPC-20-700 on either side. They are rated to work just at 60°C ambient, and have half the power density of the current driver, so I figure my chances will be better with those.

How did this compare to the version 1 (other thread) with the series parallel led strip lights from Ebay? Lumen/watt and CRI wise? I think I like the diffuse effect of that 1st version.

And did it run cooler?
Brian

Hi Brian,

I did notice an effect immediately when I compared the 2 versions. At first I did not know what it was, but then I noticed that the colors were much nicer on the Epistar version. So, yes, this version has a better CRI. Efficiency was about the same. The area where the strip lights were mounted was about the same temperature as the lampshade is now. Inside the temperature was likely a bit cooler though. As the LED area is quite big and I am using 2 of them, there is no noticable difference concerning the diffusity of the light.

Regards,

Julian

Hi!

The Meanwell 700mA power supplies worked well, but too well. 700mA seems to be a little too much, as the lampshade heated up to 70°C.
I just installed these 600mA drivers instead:

http://www.ebay.de/itm/271186668984?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Now the temperature is back to 60°C, although at am ambient temperature of 30°C. So it's a slight improvement. And they are smaller, too.

looks like we have a "who can build the most rediculous desklamp" contest going on here.
i will raise you 4 850 lumen altilons in a lamp half the size of yours and driven at 1.25a each.
pics soon!

Interesting to hear. Sounds like a really cool project!

Update: I figured that the very hot lampshade is not the best place to mount the driver. So I installed the original golden one on the last section of the arm, right above the swivel joint. I also added a solid state relais for switching the driver. I made a nice white aluminium cover for both, and it almost looks like it belongs there. I am surprised that the driver does not et war at all by itself!
My problem was, that the cable leading to the lampshade has only 3 contacts: Ground, neutral and phase. I used neutral and phase to connect the switch to 230VAC, switching the solid state relais. I disconnected ground from the lamp body, and used ground and the lamp body for the 50 something Volt going to the LED.
So, technically, the Lamp body is not earthed anymore. Would it create a kind of short circuit if the negative LED output of the Driver was earthed?

Cheers,

Julez

Without a schematic, it's hard to be sure that I understand exactly what you've got going on. However, as a general rule, the housing should be tied to the earth ground, and the earth ground should not be connected to any part of the circuit. Part of the general rule is that if any part of the circuit should touch the housing, it would cause the fuse (you do have a fuse, right?) to blow, thus protecting anyone who touches the housing.

Well, technically, I have 4 conductors. 3 of them in the original cable routed inside the lamp, the 4th being the lamp metal itself. 2 conductors in the cable I use with 230VAC to switch on and off the solid state relais, which switches the LED driver. The output of the LED driver is connected to the 3rd conductor of the cable (+) and the lamp metal (-). Because of this, I am hesistant to earth the lamp metal, although this would be a good engineering practice.
Maybe, if the driver's output is galvanically separate from the input, then I should be able to earth the lamp metal anyways. But how do I find out without frying stuff? Can I measure the voltage between the lamp metal and the earth conductor of my main power cable, and if there is no voltage, try to connect it?

The housing should not be used to carry current. The general rule, as I understand it, is that mains power should be isolated from the housing, and that the earth connection should be connected to the housing. I would expect that the LED driver would be isolated, so that would satisfy the goal of isolation. If that isolation should fail, the connection of the earth ground to the housing would keep people safe.

As to whether it is okay to connect the negative terminal to earth ground... you'd have to ask the manufacturer. I would assume that they don't plan for the user to do this, and probably couldn't predict what would happen.

An alternate technique to achieve the desired level of safety would be to use the lamp with a GFCI protected outlet.

Steve K said:

The housing should not be used to carry current. The general rule, as I understand it, is that mains power should be isolated from the housing, and that the earth connection should be connected to the housing. []

Click to expand...

Yes, that is all correct. If I could, I would have installed an internal cable with 4 phases.
I have a new driver in the mail anyways.
So I will simply try to connect the housing to ground, and in the worst case, the fried driver will set me back like $12.

Well, the grounding worked, but only on one lamp. The other one "latches" itself in the "on" state, and does not switch off even when the SS relais is clearly off. Strange...

This is so awesome. I love German task lights, and since I can't afford a light like the Waldmann Taneo, am looking to build one myself.

How did you go about selecting the LEDs for your project? I see a lot of cheap 50w and 100w LED modules on dealextreme, and not sure what to make of them. The Cree XLamp CXA3590 (5000K, 95 CRI) looks promising.

Whoa, that Cree has 77V and a max current of 1.8A. Even when run at 1A, it has double the power of my lamp.

Well, I selected relatively cheap LEDs, and only used 50% of the rated power. Later, I bought some with Epistar dies, which were only a little more expensive, but are a kind of "brand name". Not like Cree, but still.

Wow, they severely reduced the price!

http://www.wayjun.com/index.php?main_page=product_info&cPath=53_229&products_id=856

I use my desk lamp really often, and everything works just fine!