6 ms·

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. Phili

by cjsuk 9y ago

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.

Hydraulix989 9y ago
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.
- justinjlynn 9y ago
  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.
rhizome 9y ago
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.
- cjsuk 9y ago
  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.
  - rhizome 9y ago
    Thanks, I never looked into the technical reasons behind this.
Zak 9y ago
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 http://budgetlightforum.com/comment/1096106#comment-1096106
- oasisbob 9y ago
  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.
  - w458cmau 9y ago
    Which solution did you end up with?
    - oasisbob 9y ago
      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.
torrent-of-ions 9y ago
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.
- cjsuk 9y ago
  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.
- christophilus 9y ago
  This has also been my experience with Phillips bulbs.
lucaspiller 9y ago
It's not just cheap LEDs unfortunately. I bought some expensive recessed lights with Osram drivers (~€80/light), and even those flicker a little.
- cjsuk 9y ago
  This is important to know. Thanks for posting your experience.
- Johnny_Brahms 9y ago
  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.
  - seanp2k2 9y ago
    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/features/last-word/led-lamp-life-expectancy-depends-on-fixture-type-and-usage-scenario.html 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 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.
    - cjsuk 9y ago
      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!
aembleton 9y ago
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-9w-5-pack/2330j http://www.screwfix.com/p/lap-gls-led-light-bulbs-white-bc-9...
SmellyGeekBoy 9y ago
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.
- cjsuk 9y ago
  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/ 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!
sevensor 9y ago
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.
- cjsuk 9y ago
  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.

by cjsuk 9y ago

Hydraulix989 9y ago

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.

justinjlynn 9y ago
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.

rhizome 9y ago

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.

cjsuk 9y ago
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.
- rhizome 9y ago
  Thanks, I never looked into the technical reasons behind this.

Zak 9y ago

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 http://budgetlightforum.com/comment/1096106#comment-1096106

oasisbob 9y ago
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.
- w458cmau 9y ago
  Which solution did you end up with?
  - oasisbob 9y ago
    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.

torrent-of-ions 9y ago

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.

cjsuk 9y ago
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.
christophilus 9y ago
This has also been my experience with Phillips bulbs.

lucaspiller 9y ago

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

cjsuk 9y ago
This is important to know. Thanks for posting your experience.
Johnny_Brahms 9y ago
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.
- seanp2k2 9y ago
  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/features/last-word/led-lamp-life-expectancy-depends-on-fixture-type-and-usage-scenario.html 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 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.
  - cjsuk 9y ago
    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!

aembleton 9y ago

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-9w-5-pack/2330j http://www.screwfix.com/p/lap-gls-led-light-bulbs-white-bc-9...

SmellyGeekBoy 9y ago

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.

cjsuk 9y ago
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/ 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!

sevensor 9y ago

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.

cjsuk 9y ago
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.