# Flashing LED vanity lights



## Tinstaafl (Jan 6, 2008)

Got a call from a reasonably handy buddy and had to go check it out.

The bathroom vanity light (four candelabra-style lamps) was on a dimmer, and he replaced that with a switch. Did a decent job of it, and the wiring at both ends looks fine.

However, ever since he put the switch in, the lamps all flash in unison roughly once a second when the switch is turned OFF. When it's turned on, they light normally.

Lamps are Utilitech 4.5W LED.










Neutral & ground check out okay. I'm assuming there's some stray voltage being induced in the wire, whether from RF or something else. Replace just one of the LED lamps with an incandescent and the problem disappears.

Anyone ever run across this?


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## dielectricunion (Feb 27, 2013)

My kitchen light is doing this right now. It occasionally blinks (dimly) when the switch is off. In my case, im pretty sure its something wrong with the ballast on CFL i have in there


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## dielectricunion (Feb 27, 2013)

Assume it has a capacitor thats holding a charge


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## rselectric1 (Sep 20, 2009)

I am finding that LED bulbs and their side effects are becoming problematic. Buzzing, uneven dimming, and other weird things.

I've stocked up big time on incandescent bulbs until they get their act together and I suggest everyone else do the same.

I even had an LED bulb blow up and set fire to my desk lamp right in front of me. (I posted this on another thread)

I'm NOT a fan of LED's or CFL's so far at ALL. I never had these issues with good old incandescent.


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## rrk (Apr 22, 2012)

rselectric1 said:


> I am finding that LED bulbs and their side effects are becoming problematic. Buzzing, uneven dimming, and other weird things.
> 
> I've stocked up big time on incandescent bulbs until they get their act together and I suggest everyone else do the same.
> 
> ...


Same here, very inconsistent. Some work fine others seem to be haunted.


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## mstrat (Jul 10, 2013)

Interesting point that this is the second post in the past couple days pertaining specifically to the Utilitech LED's...not drawing any conclusions....but I've not had these problems with Cree or Phillips (yet). I've had a Fiet LED from Menards blow on me, scared me a tad as well!


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## Tinstaafl (Jan 6, 2008)

rselectric1 said:


> I'm NOT a fan of LED's or CFL's so far at ALL. I never had these issues with good old incandescent.


Can't argue regarding CFL's; there's no real saving grace to be found in them. Not to mention that they look stupid. :laughing:

Though I haven't done much with LED's so far, I do feel they're going to be the long term winners. IMO a good part of the problem with any of the new-tech lighting is that the engineers designing it tend to have Pollyanna assumptions about clean power and environmental considerations that just don't play out in the real world.

That'll come along eventually, but until then we just have to find ways of dealing with it.


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## griz (Nov 26, 2009)

rselectric1 said:


> I am finding that LED bulbs and their side effects are becoming problematic. Buzzing, uneven dimming, and other weird things.
> 
> I've stocked up big time on incandescent bulbs until they get their act together and I suggest everyone else do the same.
> 
> ...


In the past year or so I have probably bought 80k worth of LED's to replace incandescents, metal halides, mercury vapor etc...and have had no issues what so ever.


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## Tinstaafl (Jan 6, 2008)

griz said:


> In the past year or so I have probably bought 80k worth of LED's to replace incandescents, metal halides, mercury vapor etc...and have had no issues what so ever.


Residential use is a different animal. :whistling


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## superseal (Feb 4, 2009)

I've used some of the retrofit units from Depot sadly enough, but I haven't had any problems. 

Come to think of it...the only problem I've had with them are a slight delay in powering up off a dimmer. Regular switches seem to work fine. 

I got one in my tub surround, works flawlessly.


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## tjbnwi (Feb 24, 2009)

Install a higher quality switch. Odds are he grabbed the 39¢ box store switch.

Tom


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## Doctor Handyman (Mar 13, 2012)

Had this happen before as well. No problem with incandescent but flickered when switched off when replaced with LED ( sorry I dont recall the brand as it was 2 yrs ago).
Switch quality is a good start, mine turned out to be a shared neutral from a different branch circuit. Small enough voltage was enough to dimly flicker.


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## Tinstaafl (Jan 6, 2008)

I completely removed the new switch and the lights still flashed. Apparently the old dimmer put enough of a load on the circuit to suppress any "ghost voltage".


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## MarkJames (Nov 25, 2012)

2012 article on LED flicker. fwiw

http://www.digikey.com/en/articles/...nimizing-led-flicker-in-lighting-applications


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## CarpenterSFO (Dec 12, 2012)

That behavior is consistent with that being a lighted switch, including the behavior going away with the single incandescent bulb. The switch may not show the light without the incandescent bulb in.


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## dielectricunion (Feb 27, 2013)

CarpenterSFO said:


> That behavior is consistent with that being a lighted switch, including the behavior going away with the single incandescent bulb. The switch may not show the light without the incandescent bulb in.


 my switch thats doing the same is lighted. Great point, i didnt even think of it


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## CarpenterSFO (Dec 12, 2012)

dielectricunion said:


> my switch thats doing the same is lighted. Great point, i didnt even think of it


The voltage division between the light in a lighted switch and the drivers in an LED allows the circuit to apply a high enough voltage across the LED to load up the capacitors or whatever else is in the driver circuitry, but slowly, because the switch light has a high enough resistance to restrict the current. So the driver circuitry discharges every once in a while, i.e. flickers or blinks.

When you put in even a single incandescent bulb, the voltage division changes, and the voltage across the LEDs drops to almost nothing, and the LED circuitry won't fire.

You can switch either to a non-lighted switch, or to an electronic dimmer, which will direct the current from its internal lights or indicators either to neutral (if the box has neutral in it) or to ground (if that switch is manufactured that way).


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## Tinstaafl (Jan 6, 2008)

Getting back to the OP, this is still chewing at me. Google shows lots of hits for the problem, but no real explanation that I've found so far.

Looks like capacitive coupling provides the voltage necessary to charge up the LED driver circuitry; it fires briefly but of course there's not enough energy available to keep the "lamp" energized. The most common solution seems to be installing just one incandescent lamp in the circuit to bleed off the spurious voltage, and as it happens, that's just what I did.

I get that, but not why replacing an old dimmer with a switch would precipitate the problem.


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## Inner10 (Mar 12, 2009)

Tinstaafl said:


> Getting back to the OP, this is still chewing at me. Google shows lots of hits for the problem, but no real explanation that I've found so far.
> 
> Looks like capacitive coupling provides the voltage necessary to charge up the LED driver circuitry; it fires briefly but of course there's not enough energy available to keep the "lamp" energized. The most common solution seems to be installing just one incandescent lamp in the circuit to bleed off the spurious voltage, and as it happens, that's just what I did.
> 
> I get that, but not why replacing an old dimmer with a switch would precipitate the problem.


If you completely remove the switch and leave the circuit open does the problem persist?


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## Tinstaafl (Jan 6, 2008)

Inner10 said:


> If you completely remove the switch and leave the circuit open does the problem persist?


It does. One solution that's been recommended and actually supplied by at least a couple of LED manufacturers is a R/C load across the line to damp down the spurious voltage. Essentially the same as plopping an incandescent in, but without the watt-burning when the circuit is turned on.


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## Inner10 (Mar 12, 2009)

Tinstaafl said:


> It does. One solution that's been recommended and actually supplied by at least a couple of LED manufacturers is a R/C load across the line to damp down the spurious voltage. Essentially the same as plopping an incandescent in, but without the watt-burning when the circuit is turned on.


You just invented free energy.

Or a wire is damaged, megger it.


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## Tinstaafl (Jan 6, 2008)

Don't have a megger, don't plan to get one, and seriously doubt that's the cause.

I'm just intrigued by the fact that removing a dimmer caused the problem, while most of the complaints I've found began with adding a dimmer.


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## pappagor (Jan 29, 2008)

just ran in to the same thing last night when i was over to a buddy place


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## J.C. (Sep 28, 2009)

Tinstaafl said:


> It does. One solution that's been recommended and actually supplied by at least a couple of LED manufacturers is a R/C load across the line to damp down the spurious voltage. Essentially the same as plopping an incandescent in, but without the watt-burning when the circuit is turned on.


R/C load?


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## Tinstaafl (Jan 6, 2008)

J.C. said:


> R/C load?


Resistive/capacitive.


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