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The official Lutron support page for flickering LED bulbs says the following. Is anyone able to explain why that would help stabilize the LED lights and if there's anything similar that can be introduced into the circuit that doesn't carry the same drawbacks (i.e. is out of sight and doesn't draw much power)?

Change out one bulb for an incandescent/halogen. Because this is not ideal, this is the last resort. If you do not want to change all of your LED lamps, then you can insert an incandescent / halogen bulb into the circuit. This can help to stabilize the other LED lamps and improve the dimming performance. https://support.lutron.com/us/en/product/casetawireless/article/troubleshooting/Flickering-Flashing-Lights-with-Caseta-Dimmers-or-Switches

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  • Have heard similar advice given to smooth out generator power for electronics. Add a lamp bulb. Think because they use a constant amount of power. I think that the electronic site site give better answers, this is more they area of expertise. electronics.stackexchange.com. We are more this how to do it, they are more why it works.
    – crip659
    Apr 7, 2022 at 18:03
  • you can replace the bulb with a resistor of suitable wattage that provides a load reaching the minimal gate latching current (LI on the datasheet) of your triac. This is a more viable option w/120v grids than "220v". You could also use a smaller non-resistive load like a empty-secondary transformer if you don't care about PFC or generator efficiency and have issues with excessive heat on a resistive load large enough to play nice with your triac; the current/voltage shift of the inductive load takes more current from the triac at the lower voltage portions of the sine wave, letting it latch.
    – dandavis
    Apr 9, 2022 at 5:45

4 Answers 4

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Any dimmer requires a small amount of power for its own use.

Normally to power a switch, you need always-hot and neutral. Many light switch installations were originally wired with a classic "switch loop" -- where /2 cable is used. Plain switches don't use neutral, so on an old switch loop, they didn't bring neutral.

So most dimmers power themselves by "leaking current through the (incandescent) bulbs".

Which works fine on incandescent, since a tiny current won't make them glow enough to light. An un-lit incandescent is nearly a dead short, it gains resistance as it heats up. However, the small current makes LEDs do a variety of weird things, like glow or flash.

Thus, putting one (1) incandescent in an array of LED lights gives that dimmer's "leakage current" a viable pathway around the stubborn LEDs.

However, the same thing can be done with a bypass resistor capacitor (since it's AC). In fact, Lutron makes one of those - called the LUT-MLC. I'm a bit surprised that Lutron didn't just recommend that.

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  • Make sure to use x-class "safety" capacitors when bridging mains, rated at a voltage 25% higher than the peak of the AC sine wave. For 120v systems, that's (120v rms * 1.6 p2p * 1.2 overhead); about 230v. Or you can pay sucker rates for the same cap potted into a little plastic box with branding on the side...
    – dandavis
    Apr 9, 2022 at 5:48
  • @dandavis NEC 110.2 doesn't give you a choice there. Anyway don't overlook enclosures -- bench spaghetti may be alright at 12V, but where AC mains is concerned, packaging is a huge factor in safety, and half the design challenge. Apr 9, 2022 at 19:15
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<<<One can't say "Why" without knowing more about what you're using. One possible answer is it's likely caused by the LEDs needing less power than the incandescent lamp to operate correctly. Adding an incandescent to the circuit/switch would increase this for the whole circuit & fix your issue. If this is something that happens when the switch is off that is likely the reason. (Note: If this happens the issue could just be the wrong switch and/or light was used & can be corrected by replacing one or both.)>>>

The dimmer you're using might not be compatible with LEDs or the total wattage of your bulbs is less than the minimum required for your dimmer to work correctly.

Are the lights dimmable? How many are being served by the dimmer & what is the total sum of their wattage?

Also, does this happen with the dimmer no matter what level it is set on? or Do the lights work fine when the dimmer is set at it's highest & at some point when dimmed will flicker?

Sounds like your issue is probably the lights. But, it's hard to say without knowing which dimmer, lights & how many lights you're controlling with said dimmer.

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  • Apparently i can comment on my own post but not anyone elses. If so i would have just comment on the comment that was refering to "Why". But my guess is that's probably why.
    – MaxAMil.5
    Apr 7, 2022 at 19:29
  • LEDs are also typically powered by 2-3 volts. Not 120v. The actual voltage of your light could be any combination of lights x whatever voltage the manufacturer used for the LEDs inside. The LEDs inside & voltages will also determine if the LED is dimmable or how dimmable it might be
    – MaxAMil.5
    Apr 7, 2022 at 20:20
  • If you'll spend a few moments to take the tour, you'll see why you can't currently comment on anyone else's questions or answers.
    – FreeMan
    Apr 8, 2022 at 11:10
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The electronics that dim have a control called a gate this gate is load sensitive if there is not enough power draw across the junction the gate voltage alone is not enough to maintain the Bias that keeps the gate open ok that’s kind of technical but the main device used in dimming is a SCR or A TRIAC these have multiple solid state junctions each one requires enough voltage and a small current to maintain power to the device, when there is not enough load the gate closes early if a 60 herz flicker it is a SCR if 120 hz flicker it is a TRIAC this is because SCR’s only use 1/2 the wage form and TRIAC’s use the entire wave form so they flicker 2x as fast. This is the basics of why low draw solid state devices tend to malfunction. There are other reasons that are caused from the driver for the LED’s but those usually are non dimmable.

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  • Does this apply to uniform repetitive flickering, or would this also explain intermittent flickering / flashing?
    – g491
    Apr 7, 2022 at 21:20
  • They are the same but slightly different levels will start flickering depending on line voltage fluctuations to some extent and others are temperature related it all depends on the circuit design all electronics have leakage but that has nothing to do with a properly set up system.
    – Ed Beal
    Apr 8, 2022 at 1:29
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There are two different issues with "LED flicker":

  • Compatibility of dimming

Dimming an incandescent light is easy. LEDs are a bit harder. However, the manufacturers have mostly worked this out. You do need to make sure the dimmer is listed as "LED compatible" and the LED light is listed as "dimmable". Some brands of dimmers and lighting will sometimes work better together than others.

  • Power for the dimmer

If the problem is "flickers even when off" then this is a problem with the method used by the dimmer to get power. This is not as much of a problem with simple dimmers, but "smart" dimmers, like other types of smart switches, motion sensors, timers and other things beyond simple switches need to get power from somewhere. The options are batteries (but you have to replace those periodically), neutral (best choice, but many older houses don't have neutral in the switch boxes), ground (extremely limited for a bunch of technical and safety reasons) and leak through the circuit. "Flickers when off" is an indication of leak through the circuit, which works great with incandescent lighting (the amount of current isn't enough to make a perceptible glow) but not with LED lighting. At least some Caseta dimmers do not require neutral and they don't have batteries, which means they either use ground (but I don't think so) or leak current through the circuit when off.

As I understand it (roughly), if there is current sent through the circuit at a very low level (i.e., when nominally off, just to power the dimmer controls), with an incandescent light in the circuit the current will mostly flow through that light (a small resistance, no visible effect) and not have as much effect (and therefore less flickering) on the LED lights. The LED lights can't do much with a very little bit of power directly but (oversimplification) the driver circuits save up that power and then turn it into a short, but bright, flicker. With most of the power going through the incandescent lights, the LED effectively goes down to zero.

Solution:

If you have neutral in your switch boxes (or conduit and can pull a neutral) then look for a dimmer that requires neutral.

If you don't have neutral available, look for a dimmer that does not support remotes/3-way or other fancy stuff.

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  • "Is anyone able to explain why that would help stabilize the LED lights" (emphasis added). This addresses the "anything else" to solve the problem, but doesn't address the why.
    – FreeMan
    Apr 7, 2022 at 18:22

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