LED after glow


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Old 03-20-17, 06:11 PM
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LED after glow

A customer today asked me if LED lights have an after glow when turned off. I said I don't believe so but I never experienced it. Although I think it was mentioned (perhaps in this forum) once. Anyway, he tells me that his bathroom SATCO LED's leave a faint after glow when the switch is turned off. And that it last a long time, mabe overnight.
He insist that the switch is a standard on-off switch and no power is at the bulbs when turned off.
Did anybody hear of this and is so,what can be done about it?
 
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Old 03-20-17, 06:37 PM
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and no power is at the bulbs when turned off.
As measured with what ? It would need to be a sensitive meter.

The LED's will not glow with no power. They may stay on a few seconds after turning them off but they cannot run for an extended period with no power.

It appears that there can be enough induced power between wires to keep them on dim.
I have seen the problem with three way circuits. With a three way circuit.... the load wire is in close proximity to an always live wire.

There really is no way to stop it. If it's that annoying...... switch bulbs because they are not all affected the same way. Some claim that installing a load resistor in the circuit will stop it. It would probably work at the expense of wasting power. In that case why use LED lamps at all.
 
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Old 03-20-17, 06:51 PM
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That will also happen if you are using an electronic switch (electronic timer, Insteon/WeMo/Wink, etc) - especially if it is a "no neutral required" style, or an electronic dimmer (although I doubt you have a dimmer on the bathroom light lol!). There is a tiny amount of current always flowing, and while it is not enough to excite an incandescent or CFL, an LED is sensitive enough to glow faintly from it.

As far as an actual "afterglow", that's more of a fluorescent thing, most noticeable in CFLs. The gas inside continues to emit UV for a few minutes after the arc is broken, which makes the white coating glow faintly.
 
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Old 03-20-17, 07:00 PM
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Yes... any type of electronic timer, dimmer or wifi switch can keep an LED lit dimly. I didn't mention is as Norm said the customer had a standard switch in this instance.
 
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Old 03-20-17, 07:42 PM
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Pete, that's what he tells me, but I would not be surprised if maybe something else could be in close proximity. Both you and TAZ give me something to answer back with. Thanks.
 
 

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