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 Post subject: Re: LED stays on 24/7
PostPosted: Tue Sep 19, 2017 1:59 pm 
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Joined: Thu Aug 01, 2002 12:01 am
Posts: 2801
Location: San Jose CA
I buy the secondary excitation of the phosphors theory a lot more than I can believe stray mA level currents in house wiring faults. That other forum link was filled with anecdote and guesses by semi technical persons. It may be true that some LED can glow under very low power but an LED light bulb is a lot more than an isolated diode. a switching power supply is buried inside the base of those bulbs and the LED they use is high brightness and high power. it is really unreasonable to speculate that there could be an active glow but a passive glow from phosphors is reasonable, I have seen some lamps glow for several seconds appearing to cool off when powered down. You must have very sensitive eyes. if it is the phosphor, then a different brand buld would likely appear different in some way.


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 Post subject: Re: LED stays on 24/7
PostPosted: Tue Sep 19, 2017 7:00 pm 
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Joined: Fri Feb 01, 2002 1:01 am
Posts: 1754
Location: Mideast USA
Headboard lamp, both pictures with its switch off.

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Led lamp.jpeg
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Faint.jpeg
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Unsure if will be visible, perhaps move the angle of visual on different ambient lighting to attempt discerning the faint LEDs on in the dark picture. Touching its metal cabinet increases their brightness by about 5%. The power cord is 2 conductor, 2 prong. It is mounted on a wood piece of furniture. Of course, goes fully off when unplugged from wall. It has always behaved like that. Before moving, in another home, another city, did the same.



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 Post subject: Re: LED stays on 24/7
PostPosted: Wed Sep 20, 2017 5:55 am 
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Location: Maryland
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 Post subject: Re: LED stays on 24/7
PostPosted: Wed Sep 20, 2017 6:28 am 

Joined: Mon Dec 06, 2004 1:01 am
Posts: 294
Location: Tennessee
"The LEDs can glow with only microamps of current. One message in the linked forum post indicated that just touching some piece of metal to the input of these LED lights can make them glow from close-by AC voltages. The only question I have now is why it's intermittent."

You say there is voltage across the led lamp , but I didn't see a number, how much was there? Can you put an additional "load" across the lamp when checking the voltage? something like a light bulb in a lamp socket, just as long as it draws a half amp or better.
To me, so far, sounds like induced voltage. An additional load will cause it to drop to zero. As to why it's intermittant, the voltage could be induced from something that cycles like refrigerator, water heater, etc....
Testing it with the additional load should let you know if its induced.


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 Post subject: Re: LED stays on 24/7
PostPosted: Wed Sep 20, 2017 7:06 am 
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Joined: Sat Jul 22, 2017 2:26 pm
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gerty wrote:
"The LEDs can glow with only microamps of current. One message in the linked forum post indicated that just touching some piece of metal to the input of these LED lights can make them glow from close-by AC voltages. The only question I have now is why it's intermittent."

You say there is voltage across the led lamp , but I didn't see a number, how much was there? Can you put an additional "load" across the lamp when checking the voltage? something like a light bulb in a lamp socket, just as long as it draws a half amp or better.
To me, so far, sounds like induced voltage. An additional load will cause it to drop to zero. As to why it's intermittant, the voltage could be induced from something that cycles like refrigerator, water heater, etc....
Testing it with the additional load should let you know if its induced.


Hi Gerty:

The light base has two sockets, but I had only one bulb installed. So, following your suggestion, I put a standard incandescent bulb in the other socket, that was empty. Now, when I turn off the light switch, the incandescent goes out immediately (of course) - but the LED stays lit - and keeps that glow for a couple seconds, then goes out. So now it doesn't glow. Thanks for the fix!

- Ron


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 Post subject: Re: LED stays on 24/7
PostPosted: Thu Sep 21, 2017 9:54 am 
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Joined: Thu Aug 01, 2002 12:01 am
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Location: San Jose CA
I misunderstood the type of bulb but in this case, any thing that would put a small voltage across the diode enough to forward bias it will release some photons. Clearly the driver behind that fixture has the ability to leak when switched off but plugged in.


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