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I've had this problem and decided to test the problem away. Used a Vishay visible spectrum phototransistor and my scope. Think it was a BPV11 transistor.

Philips bulbs are 100% clean. Poundland ones are not. Cheap no brand ones from Amazon are not. The latter two have a 100Hz output.

I suspect the hatred for LED bulbs stems from the cheap ones which use the lowest cost solution to get mains voltage into a constant current which is usually a capacitive dropper and rectifier with an inadequate smoothing cap.

Really as always with these things, buy the best you can.

Also the cheaper ones seem to have a blue/white tone whereas the expensive ones have a yellow/white tone and are warmer. This helps the eyes.

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Another issue is that many LEDs have peaky spectra. This makes cool white harsh and warm white dingy. This isn't limited to cheap products, as producing a fuller spectrum with LEDs is less efficient.

I'll take the efficiency hit for better light; the most common measure used, printed on the packaging of some bulbs is CRI (color rendering index). It's based on blackbody radiation, so incandescent bulbs and sunlight both have the maximum score of 100. The average unspecified LED is in the 60s and sodium vapor lamps are negative. 90 is good for an LED, and 97 is the highest I've heard of someone testing in an LED[0].

CRI isn't the whole story on color quality, and it's possible to have high CRI with off tints or even a peaky spectrum outside of the specific colors the CRI standard tests, though the latter doesn't happen in practice. Several newer standards for measuring color quality exist, but are unlikely to be listed on a light bulb label.

[0] http://budgetlightforum.com/comment/1096106#comment-1096106

Agreed! It took several tries to get LEDs which worked well for vanity (i.e. Mirror) lighting. I thought it was a simple matter of color temperature - so wrong!

High CRI strip LED arrays are surprisingly hard to find. The end result was worth it though - skin looks natural, and the nearest commercial version is upwards of $800 - and I'm not entirely sure they got the CRI right.

Which solution did you end up with?

I ended up with a strip from colordiode, they're available on ebay. Was described as CRI>95 3000~3200K SMD2835, 90/m. Came with a pretty decent datasheet, seemed well-characterized. Cost was ~ $10/meter. They were responsive enough to include a few samples of other color temperatures with the order when I asked nicely.

The housing used was extruded aluminum u-channel by Torchstar (U05, semicircular), very nice clean finish. Available on Amazon.

Like I mentioned, this was for vanity lighting - there's a full length mirror in the closet that's wedged on the wall between a closet door and a window. Not much room for anything else. Hung two vertical strips, ~ 4ft long, on each side of the mirror.

Light ended up soft, diffuse, and flattering - but still directional enough for good modeling. Significant other couldn't have been happier.

Yeah. The best example was lighting all my clothes with LED lights. Colours seem obviously messed up. Some colours are emphasized while others are suppressed.

Low pressure sodium lamps (SOX) are negative, -44. High pressure sodium lamps (SON) are positive, +20.

Thanks for sharing, especially as it confirms my suspicions!

A few years back we changed every single bulb in our house (including the GU10s in the kitchen) to Philips CorePro LEDs. I've never seen this "flicker" or had any complaints about it from visitors (nobody even seems to notice that anything is different until I point it out). I also recently fitted out an office with SkyTile LED panels. Again, no flicker.

When I'm in a house or an office with cheaper LEDs for more than a few hours I find it very straining on my eyes. Then again, I had the same issue with CFLs, which is why I made the decision to change everything to LED in the first place.

Yeah it's the CorePro or Master ones I used. Recent ones have been these units: http://uk.rs-online.com/web/p/products/1244319/

CFLs are awful. I got rid of all of mine years ago back when LED bulbs were £20 a piece. Was worth it even at that cost!

I'd be shocked if the flicker went to 0% as this article seems to imply ("because LED flickering is even more pronounced, with the light dimming by 100% rather than the roughly 35% of fluorescent lamps") -- and I doubt the flicker for fluorescent lamps is at RMS.

There's _gotta_ be at least a smoothing capacitor after the bridge rectifier (are they actually that cheap to omit one?!). I can't find a single LED driver circuit schematic online without the low pass filter.

Often the first things to be cut in cut-rate gear are comfort/longevity features such as smoothing capacitors and protection circuits. Generally if it doesn't have an effect on the return rate, it gets cut out to slash costs.

I found the same. The ones from Screwfix work very well and only cost £10 for 5 of them: http://www.screwfix.com/p/lap-gls-led-light-bulbs-white-bc-9...

It's not just cheap LEDs unfortunately. I bought some expensive recessed lights with Osram drivers (~€80/light), and even those flicker a little.

I have a different experience. Osrams dont flicker (measured using the cheapo way: deferent types of cameras), whereas Philips LEDs do.

But otoh the osram ones have all failed or started blinking due to what I think is over heating.

Yeah, adequate cooling is actually a big deal with LEDs, and the problem is compounded in cheap bulbs with minimal cooling and lower-quality components all around. These things are supposed to last decades. http://www.ledsmagazine.com/articles/print/volume-11/issue-7... talks about this with a specific focus on the fixture, since it affects thermals so much. The LED automotive headlights I purchased recently have substantial aluminum fins and cooling fans ( https://www.amazon.com/dp/B00WVJQO58 ) plus external drivers also with aluminum cases. There are tons of cheaper options on Amazon with less thermal consideration. Given the 80w rating (for the pair) compared with the kind of heat sinking you need for a CPU with a ~80w TDP to keep it happy and below 90*C, these looked to be at about the lower end of what would do the job. The fans definitely spin fast and move a bit of air; you can hear them quite well with the ignition on and the motor off.

All the cheap ones I've had that blew up were either an SMD resistor blowing out or one of the LEDs blowing out. When the LEDs blow out if you peel the board off the heatsink you will always find a missing bit of goop under the LED that blew.

Interestingly I stuck one on my bench supply (30v 2a) and I couldn't get one to blow out at all with that!

I have multiple Osram drivers (different models) and some flicker, some don't - so I don't think as a general rule you can say "X brand doesn't flicker". I'd assume the choice of LED, and how many you have makes a difference as well, as it might be based on power draw.

This is important to know. Thanks for posting your experience.

When I bought a pack of cheap LED bulbs, the harsh flicker really surprised me. I thought cheap would mean that the diodes would be uneven in brightness and have a very narrow spectrum. I was OK with that. It had not crossed my mind that they'd decide to slice a nickel off the cost of each bulb by leaving out capacitors. Whoever designed those bulbs needs to spend a week living under their horrible 60Hz flicker as punishment.

I don't think they leave out capacitors. The typical Mylar units they use are cheap. They only put enough capacity in to get them out of the door.

the cheaper ones seem to have a blue/white tone whereas the expensive ones have a yellow/white tone and are warmer.

This is just normal color temperature and both come in all price points. I have several warm bulbs I got at Target on clearance for $2/2. I think it's just that the warm cheap LEDs are usually sold out, so all that's left are the prison-colored ones.

It's not quite that. The cheap ones use white LEDs which are basically phosphor doped blue LEDs. They have a distinct blue peak which is far brighter than the overall output. The more expensive ones use blue LEDs with separate phosphor outside the LED chip. Philips do that. Seems to result in far better filtering of the blue part of the spectrum.

Thanks, I never looked into the technical reasons behind this.

By "100% clean" do you mean no flicker, ie. they use the more expensive components? I invested in Philips LED bulbs about a year ago and honestly I can't fault them at all. I consider myself to be sensitive to things like flickering. It doesn't usually give me a headache, but it will make me notice it to the point of distracting me. I was so happy to find that the Philips LEDs were almost just like old-fashioned bulbs (instant on, no flicker, warmer colour), but with virtually no heat output and vastly reduced power consumption.

Yes 100% free of flicker. I actually measured modulation technically speaking so even brightness modulation of a small amount would have been picked up.

Same experience with the Philips bulbs here.

This has also been my experience with Phillips bulbs.

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