We bought a older home that had all the bulbs and fixtures replaced with LED lights of one kind or another. I have a ceiling fan light fixture and two pot lights in the living room that bother me. Particularly when I play with my dogs I can see the refresh rate of the bulbs. None of these lights are attached to a dimmer. Before I start buying up new bulbs, fixtures or switches I want to know exactly what I'm searching for.

I took these videos on my iPhone 6S Plus with the slow motion feature at 240 fps to clearly illustrate what I am seeing. Each video shows just a single light source being on at once. In the pot lights video the fan and fan light is off. I don't know what Youtube encoding would do to it.

Ceiling Fan light https://www.youtube.com/watch?v=DddB_0QrV_8

Pot lights https://www.youtube.com/watch?v=4FFI1atKoLE

The question I have is what exactly am I looking at. What is the terminology I need to use to describe the issue and how do I identify a solution for it? I've spent a few hours over a few weeks now reading and searching on the subject but 99% of the results are for LED lights connected to dimmer switches. Again these are not on dimmer switches.

  • Ever buy a house and it has brand-new but very cheap carpet, fixed appliances, electrical service etc.? That's because a realtor or inspector told the seller to replace those things, so the seller did as cheaply as possible to preserve their profit margin. This could be that. They could have bought cheap LEDs just to satisfy a requirement. Do they say Cree, Philips, GE or Sylvania? I bet they don't. Dec 6, 2016 at 19:22
  • Indeed that is the case. Low end stuff but the fan there seems pretty nice other than that light. The best details I can find for it are it having ~40 diodes and using 18 watts. This looks close to it amazon.com/Fanimation-LK7912BN-Levon-Light-Kit/dp/B00WROTCRE Is it just as simple as getting quality bulbs to replace them?
    – sosuke
    Dec 6, 2016 at 20:48
  • @sosuke most likely, yes, quality bulbs will eliminate the issue. Good quality bulbs from reputable manufacturers should not have a visible refresh. Dec 7, 2016 at 12:03

2 Answers 2


Well in the UK, the first of your videos is called strobing the second is flickering. My own (non clinical) tests show that dimmable light bulbs (even when not on dimmers) and both halogen and LED seem to do eiter flickering or strobing to varying degrees, some bulbs more so than others, even when on simple on off switches. I don't know if it's bad for you though, but I would rather not find out long term, so I have tested many bulbs dimmable and not and found a few bulbs which don't strobe or flicker at all, not even a small flicker, even at iphone slow motion record of 240. Unfortunately, they are all higher-end NON dimmable Led bulbs. Must be the technology used on dimmable bulbs that allow some movement within the bulb. I have not yet found even 1 dimmable bulbs of any shape or size or make that does not at least flicker to some degree (even on on/off switches) when viewed in slow motion record. Thats why I dont use any dimmers at home which is a shame but if you ever find a dimmable bulb that doesn't flicker, I would love to know :)

  • Hello, and welcome to Stack Exchange. This is interesting, but doesn't answer the question. Aug 19, 2017 at 16:01

Most likely, these are simply low quality bulbs. A good bulb will contain a switched-mode power supply to:

  • convert the incoming AC to DC
  • reduce the voltage from 120V or 240V to something lower (a single white LED requires between 3V and 5V, though sometimes multiple LEDs are placed in series to increase this)
  • limit the current, and in some bulbs, provide dimming capability.

Of course, this costs a little money. Not much: any brand-name bulb available at most stores works this way.

But a few cents can be shaved off the cost by simply putting many LEDs in series to get their required voltage as high as possible, adding a resistor or other simple component to limit the current, then putting the full AC voltage across this arrangement. This results in a bulb that blinks with each cycle of the AC waveform, 50 or 60 times per second. It's also less energy efficient.

It's also likely that with a higher quality bulb you'll get better color rendering.

Furthermore, the pot lights limit airflow around the bulb, which makes the bulbs run hotter than they would in an open fixture. Cheap bulbs use cheap components which fail more rapidly at these temperatures, and usually aren't designed to dissipate heat very well anyway. Do your bulbs weigh less than 150 grams? A good LED bulb should feel very hefty for a light bulb, since it will contain a substantial metal heat sink and often are potted.

I'd suggest going to any local retailer, and buying a bulb made by any brand you've heard of. Swap it out, and see if the problem goes away.

  • The lamp might even have a diode to produce half wave DC. That looks even worse than straight, voltage reduced, AC. Buy one good lamp and test. Its decent power supply should completely eliminate the problem. Jul 22, 2018 at 4:02
  • @WayfaringStranger The lamp is a diode: the "D" in "LED". There is no "might".
    – Phil Frost
    Jul 22, 2018 at 11:47
  • Sorry, unclear. Head went south for a moment. Some LED's may have just the full wave diode bridge: en.wikipedia.org/wiki/Diode_bridge with no capacitors to smooth out the bumps; or even just the LED on AC, which'll give you a lamp that's off at least half the time. Jul 22, 2018 at 20:07

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