Walmart’s sub-$10 LED bulb flickers and flashes

There’ve been some interesting developments in the world of LED replacement bulbs for incandescent lighting. Walmart, the world’s largest retailer, has introduced a series of four LED bulbs under its Great Value house brand. The bulbs are made under private label by TCP and manufactured in China. They come in two levels of brightness: an 800lm 60W equivalent and an 470lm 40W equivalent, with each bulb available as either dimmable or non-dimmable. The 800lm dimmable costs $9.88; The non-dimmable version is $8.88.

This review looks at just the 60W-equivalent 800lm versions and mostly just the dimmable version.

Walmart 60W equivalent 800lm LED bulb

First, a look at the bulb’s specs: The Walmart dimmable 800lm (60W-equivalent) bulb’s package says it consumes 11W of power. On the bulb’s base in fine print it says it consumes 10.5W; My Kill A Watt meter says it uses 9.3W. Why the large swing in claimed vs. actual? Don’t know.

And speaking about confusing – Why doesn’t Walmart distinguish between dimmable and non-dimmable bulbs better on the box?

Walmart 60W LED replacement bulbs

The boxes for the two bulbs are identical with the exception of the lower left-hand corner on the sides of the box with the inconspicuous labels, “Dimmable” and “Non-Dimmable”.

Walmart's 800 lumen LED bulbs' packaging

The only marking on the bulb itself is a tiny “Non-dimmable” on the base of the bulb, while there is nothing on the dimmable bulb to indicate either way. (Note the third arrow on the far left: I cover that in my packaging rant at the end of this article.)

As I switched between bulbs while testing it was difficult to keep track of which could go in the dimming socket until I marked it. This will be confusing for people with dimming and non-dimming sockets who buy both kinds.

Actually, it’s confusing while you’re still in the store: When I purchased the bulbs the checker swiped the bar code on the 60W dimmable twice because he didn’t recognize it was different from the non-dimmable bulb I was also buying, thus charging me the dollar extra. (He was apologetic and immediately corrected it.)

On to the bulb’s performance.

The bulb’s color temperature is specified as 2700K, and it seems pleasant and bright. When I first tried it on a dimmer switch it seemed to dim ok. (My first pass dimming with a dimmable bulb is to run it up and down from full brightness to full off and check to see if there are any obvious flashes or other weirdness – if the bulb can’t pass that cursory test, then I take it out and chuck it.)

So far, so good. I then spent waaay too much time checking out the color spectrum with the new (to me, anyway) ultra-interesting open-source spectrometer from Public Lab. More about that in another post. Suffice it to say that the color spectrum looked fine.

However, when I got back to checking out the bulb’s dimming more carefully the results were poor. I have four different dimmer switches: Two of very common wall-switch dimmers with the round control knob, a newer Lutron Maestro switch, and an inexpensive in-line cord dimmer. I use the wall-switch dimmers the most because they are the most common, as far as I know.

I thought I saw a flicker at the higher-brightness end and started hunting around, trying to locate a maximum flicker spot by angling a plain sheet of white paper, a trick I learned from David Biven of Cirrus Logic . (Thanks, David!) In the midst of  this “hunting” I received a phone call and left the bulb on a low power setting while I talked on the phone.  I realized after a while that the bulb was aperiodically flashing on the low setting.

Now the game was afoot: What else did the bulb do while dimming, and on different dimmers?  Here it is in what I’d call a flickering state.

Well, yuck. Flashing and flickering are not acceptable in any light bulb. I might be willing to cut the bulb some slack because there are a lot of dimmer switches out there, except that Walmart doesn’t provide a list of dimmers that they have verified it works with. So its dimming performance knocks it off my list of acceptable dimmable LED bulbs to buy.

OK, how about the light pattern? The bulb is a sno-cone design, meaning that the LEDs sit on a flat plate and project their light out like a spotlight or flashlight beam. . This means that the bulb is not omnidirectional, like an incandescent light or even like a CFL. Here’s a picture showing a crude approximation of how the light is distributed: The dark patch at the bottom should be almost completely lit. (Read this post for more on how the ring works.)

Walmart 800 lm LED bulb

I’m not completely sold on the all-encompassing importance of omni-directionality in light bulbs. For example, if you have track lights, you really want a spotlight bulb – an omnidirectional bulb isn’t as efficient.

Partially-enclosed can light track fixtures

Which brings up the one use of this bulb that I can recommend it for – a non-dimming enclosed light fixture. It’s cheap, poor dimming isn’t a factor, and the sno-cone design is actually a plus.

It’s difficult to imagine, with its lack of an omnidirectional light pattern and poor dimming performance, how the bulb can get an Energy Star qualification. Why is Energy Star so important? Because the majority of utilities in the US require an Energy Star qualification to grant a rebate to a bulb an energy-efficient bulb. (The bar is even higher in California, where the CEC require bulbs meet “California Quality”, including a high CRI, to qualify for a utility rebate.)

A sno-cone design inherently has trouble producing light that goes down towards its base. The Energy Star definition of omni-directional light is light that is evenly produced over 270 degrees (+/-135). To see why this is so difficult for a sno-cone design, let’s take a look at what lies beneath the Walmart bulb’s sturdy plastic bulb cover:

Walmart 800 lm LED bulb with cover off

As you can see, I was not able to do the usual 30 minute soak in the oven at 200F and then twist the cover off. This cover did not budge, and required cutting to get it off. This difficulty in getting the cover off is a good thing in general, because, like most other LED bulbs I’ve recently torn apart, the bulb has a non-isolated LED driver design, meaning that the  ac grid power is exposed when the cover is off. So, props to Walmart for the sturdy bulb cover attachment.

The cover is plastic; the external base below the cover is aluminum.

With the cover off, we can see the LEDs themselves and how the structure of a sno-cone design prevents  omni-directional light. 38 LED components in plastic packages sit on a metal-core pc board, which is in turn mounted on a round metal plate. The importance of this metal plate is that it transfers the heat from the LEDs’ pc board out to the round metal collar at the base of the bulb that radiates heat out to the ambient air. Note that this metal base has no heat fins as is common in other LED bulbs such as the Cree and the Philips L-Prize bulb.

Yes, the metal base gets hot: I measured 150°F with a IR gun thermometer. 150°F is similar to what I measured on the Cree bulb, but there’s a crucial difference in bulb design: The Walmart LEDs are in plastic packages, while the Cree and Philips LEDs are in ceramic packages. LEDs in ceramic packages are much more resistant to heat aging than those in plastic. Cree’s use of ceramic-packaged LEDs is probably one of the reasons it’s able to offer a 10-year warranty on its bulbs; Walmart only offers a 3-year warranty.

Because the LEDs are mounted horizontally on the metal plate the LED’s light path is limited in projecting their light downwards towards the base of the bulb. Some light ends up going down, but mostly through striking the bulb cover which acts as a diffuser. This plastic bulb cover does a nice job of not allowing the LEDs to appear as hot spots, which does happen with the Cree bulb, but it’s a consequence of the high diffusion of the bulb cover.

Here’s a close-up of the LED array, showing the connection from the driver electronics that sit below the LEDs in the base of the bulb.

Walmart 800 lm bulb LED array

Two wires carry the dc power through a hole in the mounting plate, up through a matching hole on the LED array’s metal core board. The wires are hand soldered to the top of the metal-core board, and secured with a large blob of glue. This hand-soldering of the power wires to the LED array is typical of China-manufactured LEDs; Contrast this with the clips that allow the Cree electronics to snap into place. The Cree bulbs are assembled in the US, where the relatively high cost of labor makes hand-soldering something to be avoided. However, because hand-soldering is statistically one of the biggest failure points for LED lights, the use of clips is probably another one of the reasons Cree can offer its 10-year warranty vs. the Walmart bulb’s 3-year.

Let’s continue looking at the driver electronics.

Guts of the Walmart 800 lm LED bulb

The driver is what converts the ac house power into the dc power needed by the LEDs. For dimmable bulbs, this also includes the power in the form it comes out of your dimmer switch. It’s a complicated conversion and requires that the base of the bulb be filled with electronic components. One of the key components is the IC that handles all of the power control algorithms. Because it’s the largest IC with the greatest number of pins, I suspect that the IC pictured below is the power conversion IC.

Close-up of Walmart 800 lm LED bulb power IC zoomed

It also seems to have had its identifying marks etched off. I have not as yet been able to find out which IC is used. Because the bulb is, I understand, made by TCP, an Asian bulb manufacturer, it’s also quite possible/likely that the chip is designed and made in China.

Note that the chip has 10 pins at one end, a large space with no pins, and then two pins at the opposite end. This gap in the pins probably serves to isolate the high-voltage section of the IC’s internal circuits from the low voltage.

I have not torn down the non-dimmable version of the bulb (yet), but I did notice that the non-dimming version, which sells for a dollar less than the dimmable version, has a lower Power Factor (PF): .87 vs the dimmable’s .93. This makes me think that the non-dimming version uses a different power conversion IC than the non-dimming version, but I won’t know that for sure until I tear the non-dimmable bulb down.

That’s about all I can say about the power conversion of the bulb. (Unless I find out more about the mysterious IC. Please holler if you know which one it is.)

But I do have a lot to say about the product feature decision that WalMart/TCP made.

First is the horrible package markings, or rather, the lack of them. The non-dimmable and dimmable packages are the same with only  a small bit of text in the side corner to distinguish them. Even a different color would have helped flag the two as different.

And on the bulb itself, only the non-dimmable has text identifying it as such. When the dimmable bulb gets separated from its package you won’t know whether it’s dimmable or not.

Walmart 800 lm LED bulb base instructions

Continuing on with the rant on the packaging theme, the package says, “Rated for indoor/outdoor enclosed light fixtures,” (shown in the third photo from the top in this article) while, as you can see in the photo directly above, the bulb itself says, “NOT for use in totally enclosed luminaires.” So which is it?

In summary, it’s nice to see a dimmable 800 lm LED bulb for under $10, but the performance, in terms of the bulb’s flickering and flashing, isn’t there. Pay the extra $3 for a Cree bulb and get a reasonable dimming performance and a 10-year warranty.

What about Philips’ long-awaited sub-$10 dimmable bulb?  It was supposed to be here by the end of the year,  and 2013 is drawing to a close…

Comments

  1. DriverDesigner says:

    I just opened up one of the dimmable bulbs today. It uses the SSL21082T control IC from NXP semiconductor. The topology is a non-isolated buck.

  2. Hi Margery,

    A couple of points

    1) A snocone bulb will not work well in any light fixture that relies on a parabolic reflector. Those require point sources of light. Anything less will look dimmer than the incandescent it replaces and a spot lightbeam, expected of desklamps and many tracklights, is impossible from 38 sources of light originating from a planar disk.

    2) The issue with the plastic vs ceramic packaging is not one of heat resistance, but THERMAL resistance. The LED die are in a higher thermal resistance package which means hotter LED die for a given heat sink temperature and LED. You know the rest of the story as far as lumen maintenance.

    3) The goofy symmetry in the LEDs appears to be a very lame attempt to get an extra row of substrate disks out of a panel, then having the mounting screws (which are the pressure points where the heat transfer to the main heat sink happen) accommodated. Going back to your Energy Star headscratcher, ES also requires three sampling planes of that 135 degree light distribution – I seriously doubt they’d pass if you throw that into the mix.

    4) I see the same poor solder wetting and flux residue as I’ve seen in Home Depot’s $22 GE bulbs. While you argue Cree’s connector solution is better, I doubt it is – mechanical connectors are failure points as well, especially if they are temperature cycled, have marginal contact materials, or they carry high current.

    5) The lack of markings on the IC to me seem to say these are black market chips. They could even be shipment thefts or “lost inventory” for other manufacturers. It could be as simple as inventory surplus that’s been dumped to brokers under the conditions the marking is obfuscated to avoid spoiling the market pricing. if they were “copy chips”, the labeling wouldn’t be obliterated, I’d think.

    6) It looks to me like all of the surface mount is all hand soldered as well – put those $1 a day village girls to work, and when they gain enough experience to know what they are doing and leave for better pay to go put iPhones together, go raid the villages for more of them. If you think the hand soldered wires are a rel problem…

    7) Are you able to tell us what you see for magnetics and caps? I’m especially curious about the electrolytics. Also the type of magnetics – inductor, transformer, number of leads, etc.

    8) I’m also scratching my head at the very large power resistors – thru-hole, no less, which is not a big deal when you have 60 girls with soldering irons on an assembly line. Contents of CV: “I was responsible for soldering R7 for TCP”

    OK – that was more than a couple.

    Here’s a link to how you SHOULD do a $10 dimmable American-made light bulb (yeah,it’s my design, but I also provided a fair amount of insight here so it’s not exactly spam): igg.me/at/2DLight I know for a fact that my announcement was the one that lit a fire under Walmart and others for $10 (i have an analytics report from my press release that shows Walmart clicking on it on Sept 4) a little over a month ago. Let ‘em bleed cash and build hand-soldered Chinese crap while we load the big gun :-)

    Nice teardown and insight, as usual…hope some of my gripes helped out

  3. andyT — very novel, that disc design! If you can do neodymium notch filtering of yellow
    to get better CRI like Cree “True White” or GE Reveal (without violating anyone else’s patents),
    I’m sold.

  4. Thanks. We’re focused on residential and CFL displacement right now. Can’t do everything, though the patent app has it covered and figured out

  5. my walmart only had the ND model but dims anyway. Have you had a chance to analyze the non-dimming walmart bulb?

  6. Ralph, that’s a surprise! I gotta look into that. Thanks.

  7. Reading your 3M teardown, there’s a balance struck between efficiency and compatibility. I’m got a better-than-average TRIAC dimmer so perhaps I’m lucky. It’s rated 12 amp 600 watt but specs don’t mention the holding current. At full brightness there’s a whisper hum that grows very audible when dimmed. I’ll return these bulbs when the dimmables are available.

  8. compdoc says:

    I just got the 60w/11w bulb from Wal-Mart for $4.94, and it puts off a nice light. It gets warm to the touch, but very slowly.
    The package differs a little than the one in your picture, and it says “estimated energy cost $1.32 per year” instead so I’m thinking this is an updated product.
    In any case, it feels heavy and solid and works so well that I’m going back for more after the holiday. I want to replace the CFL bulbs installed in lamps that could get knocked over, to lower the possibility of mercury escaping. And as the other CFLs I have burn out, I’ll replace those with LEDs too.
    LEDs are still too expensive to take over the market, but that should change before long as production ramps up.