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LED light bulbs, odd observation
By Volvo farmer, Section Light Posted on Tue Nov 03, 2009 at 05:44:21 AM MST
What's going on here?

Local wholesale club had "Lights of America" LED lights (made in China) 3 for fifteen bucks, so we bought a pack. Not very bright, but only 1.5W per bulb, pretty nifty for us off-gridders.
So I installed them and when it got dark, I noticed they are just a little bit on, This is a horrible picture but you get the idea

They don't do this in any other fixture. This one is controlled by a 3-way switch. Is there any chance that I'm getting a tiny but of voltage at this socket because of inductance? There's a good 50' of wire between the 3-way switches.
My electrician had an IQ of about 80 and there's switches in this house that I still don't know what they control. I realize it's all a guessing game, but I just wondered if I should start looking for a problem with my wiring or switches, or if maybe this might just be caused by normal inductance.

LED light bulbs, odd observation | 13 comments (13 topical)

Re: LED light bulbs, odd observation (3.00 / 0) (#1)
by wooferhound on Tue Nov 03, 2009 at 06:30:58 AM MST

I was playing with some Long Wire generation experiments awhile back. I found that I was getting DC voltage between long wires and ground. so I decided to try hooking up a red 2volt LED to see if there was any real power there. The LED glowed fairly good but was not usable. I observed the LED during a Thunderstorm and it Flashed significantly with every Lightning strike. So if your light flashes during a Lightning Storm then you are be getting this effect somehow.
http://www.fieldlines.com/story/2008/7/24/01353/8229

It may also be the on/off switch leaking the AC a little bit. if that is the case then the LEDs should be flashing at the line frequency.
W o o f -={(
Huntsville Alabama U.S.A.

Re: LED light bulbs, odd observation (3.00 / 0) (#2)
by bob golding on Tue Nov 03, 2009 at 06:41:56 AM MST

i have noticed this effect with a led striplight as well i assume it is the caps discharging, but havent looked any further into it i am off grid and am using an inverter rather than grid power

bob

Re: LED light bulbs, odd observation (3.00 / 0) (#3)
by DanG on Tue Nov 03, 2009 at 07:23:30 AM MST

Time to get an analog volt meter out and check outer shell of the light socket for potential. I've got knob and tube wiring still buried deep in this 1916 house and have all sorts of random small voltages everywhere. Kind of off-putting to see electric fixtures wired the way one would plumb a hot water radiator! I've noted here with some LOA high-Kelvin temperature (bluer) 120VAC LED lamps their phosphors continue to glow for some time after power off.

Re: LED light bulbs, odd observation (3.00 / 0) (#4)
by TomW on Tue Nov 03, 2009 at 07:43:23 AM MST

Not too hard to bug this out if the lights are on AC house circuit it might have been wired incorrectly and have a screwy nuetral to ground bonding. He may be switching the nuetral too?

The way to wire a 3 way is probably on google.

Tom

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

Re: LED light bulbs, odd observation (3.00 / 0) (#5)
by rossw on Tue Nov 03, 2009 at 07:27:30 PM MST

The wiring of the place is almost certainly fine.

I have a number of (similar) units here in my offgrid home in Australia.

My place is different - I have all CBUS controls - so all my lights are actually through computer-controlled dimmers. The LED lights remain on quite brightly even when turned off.

The reason for this is because the snubbers across the triacs (required to meet EMI emission standards) have enough leakage for these ultra-low power devices to sort of work.

I'd be absolutely unsurprised if 50' or more of cable with parallel conductors (as would be used in 2-way or 3-way wiring) had enough capacitance to leak enough current to light your LEDs, albeit dimly.

The usual "fix" for this in home-automation circles, is to put either a small incandescent lamp (5W pilot for example), or a small capacitor, across the load.

Re: LED light bulbs, odd observation (3.00 / 0) (#6)
by FishbonzWV on Wed Nov 04, 2009 at 04:37:10 AM MST

VF,
Does your three way switch have a little neon in it?
I put 3 of those and a 3.5w one in a circuit with a lighted three way switch.
Mine glow also and I think the neon light in the switch allows enough current to dimly light the leds. They make a nice night light for the stairway that they're installed in. I had thought about changing the switch out but decided to leave it.
I've got 8 of the 3.5 watt ones in now, they're replacing 15w CFL's that replaced 60w incandescents.
Bonz

Re: LED light bulbs, odd observation (3.00 / 0) (#7)
by SparWeb on Thu Nov 05, 2009 at 07:28:11 AM MST

Despite what Ross said, I too would start with the neutral (white) wire and see if it floats a bit above 0v. Set the DMM (depending on what type you have) to progressively lower VAC ranges so that you don't zap it. Test inside this socket, test other sockets / receptacles on the same circuit. Test when the breaker is set to "off", if you aren't getting to the bottom of the mystery. You can also buy plug-in outlet testers that light up green/orange/red depending on the fault conditions they discover. Some are more sensitive to the ground-fault condition than others.

The neutral in my house has been non-zero, too at times. I found some wiring errors in the house when I moved in, which are mostly fixed now.

It's not always the fault of the electrician. Heavy loads on the same circuit will cause a voltage drop on the current run through the hot wire AND the return wire. That voltage drop then appears on all other devices on the same circuit. Once that load shuts off, the neutral goes back to 0v.

Steven Fahey

Re: LED light bulbs, odd observation (3.00 / 0) (#8)
by tanner0441 on Thu Nov 05, 2009 at 07:44:25 AM MST

One point, are there any high powered radio transmitters in your area, with 50ft runs of cable between switches it could be acting as an antena, the diodes don't care what the frequency is as long as it developes enough voltage.

I have seen flourescent lights glow and flicker in houses close to Local radio and TV antenas..

Brian.

[ Parent ]

Re: LED light bulbs, odd observation (3.00 / 0) (#9)
by ghurd on Thu Nov 05, 2009 at 08:55:44 AM MST

I doubt it... Any chance it is on a GFCI circuit, or one of the switches has a neon in it?

It takes almost 0A to light them that bright.
I have 12V 15 LED (both red and amber) bulbs that light brighter than that with power flowing from my right index finger on the battery to my left index finger on the bulb, with the bulb neg to bat neg.
I'd post a pic if I had a 3rd hand to push the camera button.
G-
Ghurd.info

Re: LED light bulbs, odd observation (3.00 / 0) (#10)
by thirteen on Fri Nov 27, 2009 at 05:55:22 AM MST

As an idea could one of your appliances be back feeding your lights with what I call ghost voltage. Some things will send a small voltage back thru the lines. Could you possibly have a switch going bad? Just an idea to ponder.

Re: LED light bulbs, odd observation (3.00 / 0) (#11)
by Opera House on Thu Jan 28, 2010 at 12:21:50 AM MST

"This one is controlled by a 3-way switch"

This implies you have a long length of parallel conductors, one with power and the other connected to the lamp. That is more than enough capacitance to operate the lamp. Only a couple micro amps is enough to light a LED. Best solution is a 0.1 (X2 rated across the line cap). It is always a good idea to put a47-220 ohm resistor in series with the cap for longer life.

Re: LED light bulbs, odd observation (3.00 / 0) (#12)
by don1 on Sun Feb 14, 2010 at 02:53:43 PM MST

Well I think it is your LED's saying , See how efficient we are, We can even light up without the switch turned on. See how much you need us in your home :)
Don thinking wayyyyy outside the box.
Don

Off topic -- switches. (3.00 / 0) (#13)
by sbotsford on Sat Feb 20, 2010 at 02:14:27 PM MST

Hi VF. Would have sent you a private message, but haven't figured if that's possible on this board.

I have several switches that took me a long time to figure out.

1 controls a pair of flood lights under the peak of the house. Didn't figure that out until I changed the bulbs.

1 turns off all the outside plugs.

1 turns off some of the living room plugs -- but these are set up as split duplex plugs so the swtich turns off the lower, but not the upper outlet.

Finally one is still unknown. Go figure
Always listen to experts. They'll tell you what can't be done, and why. Then do it. -- Robert A. Heinlein

LED light bulbs, odd observation | 13 comments (13 topical)

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