Click MR16 LED Globe Failure Post-Mortem

RE: Click MR16 LED Globe Failure Post-Mortem

shabaz — Thu, 02 Jun 2016 01:19:07 GMT

We should have a section at element 14 for discussing different lighting product experiences and feedback. Although a lot of home lighting experience could be subjective though, so hard to compare.

Much like [mention:8fb233e8974445138ef0af2b63b49f94:e9ed411860ed4f2ba0265705b8793d05] I too am in no hurry to swap conventional lighting at home for LED. But kind-of giving LEDs a trial currently in one room. The previous lights were incandescent, 40W or 60W (depending on what is available off-the-shelf - the 60W are getting rare in the DIY stores) x 5 lamps, which reflect off walls, not down spotlights.

I went for these ones, the R50 version in the photo below: RefLED Blown Reflector | Sylvania Lighting Solutions

[View:/resized-image/__size/620x428/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0ec0e0a0-92e0-4036-87f1-f779ba0fceb9/2018.contentimage_5F00_181506.png:620:428]

These ones are not perfect for all rooms, they are not suitable for dimming with an incandescent lamp dimmer.

The feedback so far is semi-neutral to positive depending on who I speak to.

The consensus is basically it is definitely brighter. Those who are neutral overall say the color feels too white/unnatural, and the color or effect (could be CRI related or color temperature related, I can't decide) has a slight feel of ugliness like some economy CFLs have. I can see that too.

I get the feeling that without mixing LED colors*, this problem would be hard to get rid of. I'm not sure though, and will try some more lamps.

I might also swap back to incandescent for a bit, and see what the feedback is then..

* maybe separate color lamps, e.g. dimmable red, to mix with white LED lamps could be an option too, to try to correct things. More awkward though.

RE: Click MR16 LED Globe Failure Post-Mortem

shabaz — Wed, 01 Jun 2016 11:36:00 GMT

Hi!

Interesting analysis. It would be good to examine the Vf of each LED too, because there is a school of thought that it is ok to parallel up LEDs without resistors under certain conditions.

Although the Vf variation can be large between LEDs, it is possible to get them binned from the manufacturer so that the variation is much smaller. In that case, the series resistance can be

much smaller. A point can arrive (in theory) where there is enough effective series resistance in the LED characteristic curve itself to be sufficient that the current delta (even under

junction temperature deltas due to the imbalanced current) is small enough to be within the rated spec for each LED.

It is hard finding this information though, it most likely needs to be tested. The best link I could find is here:

The Nuts & Bolts of LEDs—Part III | EDN

Notice however that still their conclusion is that so-called active control (i.e a constant current source) is preferred, but then the author does work for a semiconductor manufacturer - he's still

right of course, active is good.

However, that doesn't mean the series resistor method is bad, it just means a lot of care is needed, i.e. more expensive LEDs (since you're paying for the fact they are binned) and some calculations.

For example if you can bin to within tens of mV (this should be feasible, especially if they all came from the same wafer) and can adequately heat sink, and your LEDs happen to have

ESR in the right ballpark, then that means you could reduce or even eliminate the external series resistor. A lot of 'if's of course, but worthwhile the manufacturer doing if it saves them costs

and simplifies the circuit if they are manufacturing hundreds of thousands.

It could be that to save costs the low-cost China models are not binned, but if the LEDs are manufactured close-by then maybe they can purchase a whole batch, so that consecutive LEDs are

all from the same wafer and therefore naturally very well 'binned'. This is speculation though..

RE: Click MR16 LED Globe Failure Post-Mortem

mcb1 — Wed, 01 Jun 2016 09:17:33 GMT

Nice breakdown of the fault.

Unfortunately LED technology is rather pricey and the alternatives like this give the consumer a bad taste.

I still believe the LED lamps for domestic use have a long way to go before they are equal to what they are replacing in most applications.

The biggest waste was downlights which were designed to not throw light across the ceiling and show the lower quality finish.

Unfortunately it requires twice as many lights, hence is a power waster.

I think your links are fine as the item is not an element14 sold product.

Mark

RE: Click MR16 LED Globe Failure Post-Mortem

jw0752 — Wed, 01 Jun 2016 06:34:00 GMT

Hi Gough,

I am hoping that they do as good of a job figuring out what went wrong with me when I stop ticking as you performed on the LED globe. This is a great learning experience to follow your dis-assembly and analysis of the light.

I am glad that you are bringing some of these links to your web site onto the Forum.

John