I have two LED lamps in my corridor, and when I switch them off, they keep emitting light (not very strong, but it's annoying at night).
What can it be? How can I fix it?
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1I forgot to mention that the lights are turned on from both sides of the corridor, by a commuter circuit. I don't know if it has something to do with it, but just in case I provide the info... Thanks!– opalenzuelaJul 31, 2013 at 15:59
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1I've often heard the term 'ghosting' used to describe the effect.– J. PolferJul 31, 2013 at 16:38
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@J.Polfer so you're saying he needs an exorcism?– JasonJul 31, 2013 at 20:34
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Wait, do you mean the lights glow for a moment after you turn them off (normal for LEDs), or they stay on (but dim) indefinitely?– HankJul 31, 2013 at 22:16
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It's not for a moment, it's permanently. I cannot measure it exactly, but I'd say that when switched off they are emitting around 10% of the amount of light that I get when they are switched on.– opalenzuelaAug 1, 2013 at 7:18
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3 Answers
Some light switches run a small amount of current through the bulbs even when off, usually to power small devices at the switch like a timer, motion sensor, or night light. Do your switches have either of those features, or something else like that?
The way those devices work is instead of having a hot/neutral pair powering the switch, they just sit inline with the hot wire and draw a very small amount of power. Old fashioned incandescent bulbs won't light up if there's only a small amount of electricity running through them, so you would never notice this current, but LEDs are much more efficient and apparently are getting enough power to run.
If that is the cause of the problem, there are a few solutions:
- Swap out the light switches for regular ones. You'll lose whatever additional functionality they have.
- Upgrade your switches to ones that have both a neutral and a hot wire, instead of just the hot wire. This may be relatively straightforward or extremely difficult, depending on whether the neutral for the light goes through the same box as the switch. (Note that even if you do have a neutral at the box it may be a little tricky to wire it up, since you might have to cut it and then add a pigtail or two.)
- Put back your old-fashioned incandescents.
- Install one incandescent and one LED
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3I ran into this with a light controlled by a motion detector; it turns out that there are some motion detector switches labelled as LED compatible to solve for this. I took option #3 for now and deployed the LED fixture elsewhere.– TomGAug 1, 2013 at 1:17
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6This was it! My switches do have a night light. I just had to remove it and the effect went. Thank you very much!! PS: @J.Polfer, no exorcism required this time ;) Aug 1, 2013 at 7:22
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@opalenzuela how did you remove the night light feature? I really can't see how I can do that on the inline switch I have. See pics: i.stack.imgur.com/EWlJj.jpg and i.stack.imgur.com/hgUW4.jpg– AdrianoNov 23, 2018 at 17:16
If we're talking a high voltage circuit, w high intensity LEDs: Many high intensity white LED's use a phosphor that is in fact phosphorescent, like glow in the dark paint. You just have to wait for it to dim down. Switching to a different brand of bulb, with a different phosphor may help, but it's hard to "try before you buy".
If we're talking a low voltage circuit, 5-12v: A capacitor in line with an LED can power it for quite some time. You can limit this effect by by using a power supply with a smaller filter capacitor.
answered Jul 31, 2013 at 20:36
If the light is controlled by 3-way switches wired with a 3 wire conductor, the electromagnetic field will induce enough voltage on the other wire to dimly light an LED bulb.
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