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The scientific reason you don’t like LED bulbs – and the simple way to fix them

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Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#21

Post by lucaspiller »

cjsuk wrote: post #8

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 cu…

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

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#22

Post by seanp2k2 »

Osmium wrote: post #7
oppositelock wrote: post #3

Earlier quoted context omitted.

Me too - constant headaches from fluorescent lights, none from LED. I buy the less efficient full-spectrum LED lights which have a phosphor. The phosphor probably filters the underlying LED flicker.

Yeah, I think my Ikea ones are phosphor, the Philips Hue are RGB though and still fine.

Anyone know what the LiFX bulbs use? We have a dozen of them and the adjustable color temp is great. I also have a box of smaller LED bulbs from Home Depot. Neither hurt my eyes and I don't (didn't, will see now that I'm paying attention) notice a difference, but I'm sure there is one.

I also wonder about e.g. The Anker desk lamps, where the bulb is built in. I have one behind my monitor with the head turned round (it's designed to do this) to throw light up the wall behind my monitor as bias lighting, and another (their clamp lamp) on my electronics desk. They're great lamps with annoying touch power buttons, but both are adjustable color temp and have built-in LEDs which never require changing.

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#23

Post by cjsuk »

torrent-of-ions wrote: post #18
cjsuk wrote: post #8

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 cu…

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 bulb…

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.

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#24

Post by cjsuk »

lucaspiller wrote: post #21
cjsuk wrote: post #8

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 cu…

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

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

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#25

Post by perilunar »

zkms wrote: post #9

I hate it when LED light output isn't continuous or visibly flickery, especially when it's from LED lights that are on (or are visible from) moving objects -- such as LED taillights on automobiles or in-road lane lights. All the eye movement (or object movement) makes the flicker even more flagrant :( I remember extremely flickery lane lights on the leftmost lane markers on California's infamous SR 110, on the northb…

Those LED plots are pretty crazy. Surprising how much incandescent lights vary though (10-20% according to the plots) — would have it would have been much less than that.

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#26

Post by anon4728 »

abainbridge wrote: post #16

What gets me are side-lights on cars that flicker. Cars have DC electric systems in the first place. Where did the Audi engineers find 100 Hz to run the LEDs from? I guess there's a switch mode power supply to convert down from 12 V to something lower that the LEDs need. But AFAIK, switch mode power supplies don't switch at 100 Hz. I'm pretty sure you could show by experiment that flickering car side-lights are distr…

It could be a boost converter if the LEDs are in a series&parallel configuration to save money.

PROS

Higher voltage is great because the conductors can be smaller.

CONS

Higher voltages need sufficient insulation.

Circuit maybe more dangerous after a collision.

Long series of components is bad because one component going open-circuit takes out all others on the same string.

---

There are also other technologies like LED filaments which appear like a continuous light with less ability to see individual elements.

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#28

Post by pvdebbe »

kabes wrote: post #20

But then wouldn't our 60Hz screens have a much bigger impact on office workers than the lights above them?

The screens have separate backlight which is done with other technologies and if with leds, definitely with higher frequencies than 60 Hz.

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#29

Post by inferiorhuman »

Osmium wrote: post #7
oppositelock wrote: post #3

Earlier quoted context omitted.

Me too - constant headaches from fluorescent lights, none from LED. I buy the less efficient full-spectrum LED lights which have a phosphor. The phosphor probably filters the underlying LED flicker.

Yeah, I think my Ikea ones are phosphor, the Philips Hue are RGB though and still fine.

I went to LEDs in my apartment about two years ago. 3 Hue bulbs + hub, some 48" T8 LEDs, and some E26 Ikea bulbs. The Ikea bulbs are great, power on instantly and slowly fade off. The T8s take about 3/4 second to turn on, and are nice and bright (and a far cry from the power consumption of the T12 florescent bulbs they replaced).

The Hue bulbs... well, one's developed a noisy transformer. Replacements are, what, $40? Meh. I like the Zigbee integration, but not $40 in two years worth of like. And the CRI of the Hue is just as bad (actually worse) than the other bulbs.

Lesson learned, those Ikea bulbs are great.

Re: The scientific reason you don’t like LED bulbs – and the simple way to fix them

#30

Post by tech2 »

kabes wrote: post #20

But then wouldn't our 60Hz screens have a much bigger impact on office workers than the lights above them?

Screen refresh rate (rate that each image is replaced) is a lot different to the frequency of the PWM applied to the backlight. If the backlight were pulsing at 60Hz people would be _very_ upset.
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