CREE BULBS AND FLICKER

I am going to post my full results shortly, but wanted to see if anyone else out there can do a test and confirm what I found before I post my results.

I have been testing a bunch of bulbs that I have for flicker and wanted to get a hold of a Cree LED bulb before posting my results as there are reports on the web of excessive flicker.

I finally picked one up (60W equivalent, warm white).


Soooooo ..... with photodiode connected to the scope, and Cree bulb directly connected (no dimmer) ..... I had to do a double take and check everything as I thought I was picking up electrical noise.


RESULT: On a relative basis (no absolute units), I was measuring peak to peak flicker of 800 units on a 1200 unit average output. That's bad ..... we are talking cheap Christmas Lights bad. For reference, on the 60W equivalent Philips Alien Head, I could not detect any flicker, and would estimate it to be less than 1%. I know I can easily and reliably measure under 5% flicker.


Interested in anyone else's feedback. I may take this one back and get a different one to see if it is single unit issue, but then again it could be a single lot issue (many bulbs) so another independent test from another area is more likely to result in a different lot.


Looking forward to comments.

Semiman

I have the same bulb. Yes it flickers. Quite a bit.

120Hz?

Gordon

Yes 120Hz.


Semiman

SemiMan said:

...I was measuring peak to peak flicker of 800 units on a 1200 unit average output [at 120 Hz]. That's bad ..... we are talking cheap Christmas Lights bad.

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That sounds bad, but not as bad as cheap Christmas lights. Cheap Christmas lights are half-wave circuits, so their flicker is at 60 Hz instead of 120 Hz, and the cheap Christmas lights I've seen have no filtering at all, so the peak-to-peak intensity is greater than the average value...

I'll try and repeat your photodiode/scope test on a Cree 60W this week...

SemiMan said:

Interested in anyone else's feedback. I may take this one back and get a different one to see if it is single unit issue, but then again it could be a single lot issue (many bulbs) so another independent test from another area is more likely to result in a different lot.

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It's not just your bulb. I have one of these and the flicker is very obvious.

This was the one big mistake I was hoping LED bulb manufacturers wouldn't make. You would think they would have learned from history. One big complaint about fluorescent lighting was flicker. Electronic ballasts were developed partially to eliminate flicker. There's zero reason why an LED bulb should flicker when it's simply a matter of using a larger filter cap. Seriously, what will that add to the price, 25 cents? Everyone would be willing to pay a quarter more for a bulb which doesn't flicker. I hope Cree fixes this problem as soon as possible. I'm not even seeing why cheap Christmas lights should flicker when we're talking about adding a part which costs pennies to prevent it.

jtr1962 said:

This was the one big mistake I was hoping LED bulb manufacturers wouldn't make. You would think they would have learned from history. One big complaint about fluorescent lighting was flicker. Electronic ballasts were developed partially to eliminate flicker. There's zero reason why an LED bulb should flicker when it's simply a matter of using a larger filter cap. Seriously, what will that add to the price, 25 cents? Everyone would be willing to pay a quarter more for a bulb which doesn't flicker. I hope Cree fixes this problem as soon as possible. I'm not even seeing why cheap Christmas lights should flicker when we're talking about adding a part which costs pennies to prevent it.

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JTR, I will post my other results shortly after I rerun them. I always feel better running tests twice and I want to change my photodiode to one that has more of a photopic response or at least close.

It is not just a matter of a larger filter cap, bit is a matter of power supply topology and hitting the target power factor correction. It's actually easier to do that with a small cap versus a large cap as it ensure you have load through more of the cycle.

I am disappointed though. I think I have average flicker sensitivity ... some of the early DLP projectors I found off, but not to the level some did. I just don't think for a few dollars this is the type of sacrifice I want to make when the Philips Alien head exhibits 0 flicker.

Semiman

Philips has introduced some cheaper bulbs which do flicker. I'd be curious what results you get from the 420240/424895.

Did you measure the power factor of the Cree bulb? My Kill-A-Watt reports about 0.9. Not sure how accurate that is. It seems to be off by a watt or two when measuring power consumption.

While I suspect the drivers are the same between the two parts, I can't detect any flicker on the 5000K model (which only means so much). Has anyone done any testing on this particular model?

It seems like phosphors should help visually "buffer" the flicker since they have an on/off lag time (I've certainly seen it on some direct-drive LED's). Wondering if the phosphor mix on the 2700K part aggravates the affect or if the 5000K phosphors mitigate it?

Ok, I tried to get my o'scope running to no avail so I hooked up a silicon solar cell to a pair of headphones and this is what I got:

Cree 60w ww 120hz hum (I tried a couple of them)
Philips 10.5w 120hz hum
Philips 11w dimmable - a little bit of 120hz hum
Utilitech Pro 800 lumens - 120hz hum
Utilitech Pro 450 lumens - no hum
Utilitech 1100 lumens - no hum
Utilitech 1600 lumens - no hum
Philips AmbiLED alien head 12.5w - no hum
Philips AmbiLED alien head 17w - no hum

A couple of the no-hum bulbs made a quick "fwoop!" in the headphones when first powered up, but otherwise quiet as a mouse.

PhotonWrangler said:

Ok, I tried to get my o'scope running to no avail so I hooked up a silicon solar cell to a pair of headphones and this is what I got:

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Clever...

idleprocess said:

While I suspect the drivers are the same between the two parts, I can't detect any flicker on the 5000K model (which only means so much). Has anyone done any testing on this particular model?

It seems like phosphors should help visually "buffer" the flicker since they have an on/off lag time (I've certainly seen it on some direct-drive LED's). Wondering if the phosphor mix on the 2700K part aggravates the affect or if the 5000K phosphors mitigate it?

Click to expand...

Went over this a while back and found out the phosphors have almost 0 lag ... uSeconds at best. They are fluorescent, not phosphorescent. Any lag is your eyes/caps.

PhotonWrangler said:

Ok, I tried to get my o'scope running to no avail so I hooked up a silicon solar cell to a pair of headphones and this is what I got:

Cree 60w ww 120hz hum (I tried a couple of them)
Philips 10.5w 120hz hum
Philips 11w dimmable - a little bit of 120hz hum
Utilitech Pro 800 lumens - 120hz hum
Utilitech Pro 450 lumens - no hum
Utilitech 1100 lumens - no hum
Utilitech 1600 lumens - no hum
Philips AmbiLED alien head 12.5w - no hum
Philips AmbiLED alien head 17w - no hum

A couple of the no-hum bulbs made a quick "fwoop!" in the headphones when first powered up, but otherwise quiet as a mouse.

Click to expand...

That get's the brilliant of the day award!

Semiman

SemiMan said:

Went over this a while back and found out the phosphors have almost 0 lag ... uSeconds at best. They are fluorescent, not phosphorescent. Any lag is your eyes/caps.

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Remote phosphor panels on the Philips alien-head will glow in the dark very briefly when charged by an external light source. I discovered this when I left mine under the desklamp and it glowed just visibly for perhaps a second when I switched the lamp off - then tested it a few times keeping my eyes closed until the moment the external light source was switched off. Of course, no other white LED I experiment with seems to exhibit this property, so perhaps it's a moot point.

brickbat said:

That sounds bad, but not as bad as cheap Christmas lights. Cheap Christmas lights are half-wave circuits, so their flicker is at 60 Hz instead of 120 Hz,

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These Christmas lights are horrible. They have a pulsating effect that is difficult to describe, and unbelievably annoying to look at. Some people apparently are oblivious to it (or just don't seem to care), but I absolutely can't stand it. It is very strange, it must have some subconscious sensory effect.

The higher quality rectified (120 Hz) lighting strings are better, but some flicker is still perceivable if darting your eyes from one focus point to another.

I have not tried this Cree LED bulb, but of the several different LED bulbs I do have there does not appear to be any perceivable flicker.
(well, actually one time I brought an Osram 230v LED bulb to another country with 120v outlets and surprisingly the LED bulb worked just fine, seemingly at full brightness, but with some barely noticeable flicker)

+1 on the cold-white Cree bulb having no obvious flicker. I'm usually able to detect flicker below a few hundred Hz.

I have a cree 60w ww in my porch light,and I dont see any flicker when viewing the bulb directly,nor when looking at the wall washed with light? Note,this is NOT on a dimmer.

Forgot to mention that I tested the 3M bulb also and I heard 120hz hum.

Qship1996 said:

I have a cree 60w ww in my porch light,and I dont see any flicker when viewing the bulb directly,nor when looking at the wall washed with light? Note,this is NOT on a dimmer.

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Very few people can detect 120Hz flicker in a stationary environment (almost none). Where you will detect it is with motion.

Semiman