Strobing LED lights

[Brian G Turner]

So we get a new kitchen light unit installed, along with a new dimmer switch and new dimmable GU10 LED bulbs.

However, there's a slight strobing effect when the lights on - not noticeable, except with fast movement - such as running taps, or if you shake your hands to show it.

I've googled this but only found general articles suggesting it can be either the dimmer switch or the bulbs.

I'm tempted to think it must be the bulbs as they were just cheap ones off Amazon - it was very hard to get what I needed elsewhere, such as Argos or Screwfix. Besides, I would trust a qualified electrician knows to put the right dimmer switch in!

However, any one any experience of this, and what the root cause might be?

 

[Foxbat]

If it's a standard dimmer switch, that's your problem. It needs to be a dimmer specifically designed for LEDs. I have LED bulbs in the house now but haven't gotten around to changing the dimmer switches. There is, as you say, a strobing effect. The best way to minimise it until an LED dimmer is fitted is to turn the dimmer up to full brightness. This decreases the effect quite a bit.

I really must get my finger out

 

[mosaix]

I think @Foxbat is correct. We stayed in holiday accommodation last year and suffered the same. They had the switch changed and it cured the problem straight away.

 

[farntfar]

Contrary to what you may imagine, a standard dimmer switch doesn't reduce the light by lowering the voltage going through the light bulb, but rather uses a thyristor to turn the voltage off during part of each cycle (ie 50 times a second, part of the sine wave is just cut out)

With a standard incandescent bulb this has the same effect as the filament can't react fast enough for you to notice.

But with LEDs, this switching on and off is apparent to your sight, and a 50 Hz strobe is created, of increasing noticeability, as the dimming is increased.

The thyristor works well for incandescent bulbs, but a different type of dimmer is required for LED bulbs, specifically to avoid this effect.

 

[Brian G Turner]

Just wanted to mention that we had a new dimmer switch put in that was supposed to be specific for LED bulb use. If that's the case does that change anything?

 

[Dave]

I can't help, but I'm interested as it is difficult to buy incandescent bulbs anymore, especially those with a high wattage. We used to have a Globe bayonet fitting 100w incandescent lamp on a dimmer that worked fine. When it went and I tried to replace this, the only bulb that I could find (and I've looked absolutely everywhere) flickers just like you say when turned down (even though it said on the box that it is suitable for use with a dimmer.) I'm now, after reading this, thinking that I need a different kind of dimmer switch.

 

[Swank]

Just wanted to mention that we had a new dimmer switch put in that was supposed to be specific for LED bulb use. If that's the case does that change anything?

I work with electricians and saw them dealing with this problem recently. Either the dimmer or the fixture was faulty.

Really low voltage stuff can be kind of spooky in operation.

 

[tinkerdan]

I suspect this has something to do with refresh rates.
Much the same as with those old monitors that would give you a headache at certain refresh rates.
You might find this to become more expressed if you film something under that light because the recording will really pick it up.(not as adaptable as our eyes are.)

Here in the US I've a couple used with a standard dimmer; however I don't use those that often and have never noticed strobing.
One is a walk-in closet off the bedroom and I keep it dim in the morning so as not to wake someone else and turn it off after I make my selections.

 

[tinkerdan]

The End of Flicker

Although you might not be able to see it, LED flicker can be hazardous to health, safety, and performance.

medium.com

 

[tinkerdan]

Now for just an interesting side note.
One of the neighbors just knocked on the door--at 500 am--I checked outside and they are standing on the porch and there seems to be some strange strobing light going on.

I often leave the porch light on all night now that the led lights work so well and cost less to use.
This one had gone bad and is now strobing like an emergency light so the neighbor--just coming home from a late shift decided to find out if everything was okay. I thanked them for taking the time and changed the bulb.

This got me to thinking that as we get older--maybe we should install some sort of light just like that if anything goes amiss.