Why Do LED Lights Emit Light When Switched Off?

[John1397]

I have Led lights in the house ceiling fixtures running on household AC when the are switched off they still give a small amount of light am I paying for this current or is this current that would have been lost anyway?

John

 

[DaveC426913]

I have Led lights in the house ceiling fixtures running on household AC when the are switched off they still give a small amount of light am I paying for this current or is this current that would have been lost anyway?

John

You are paying for it. It has many names such as standby power, but I've also heard it called phantom load.

http://en.wikipedia.org/wiki/Standby_power

Every once in a while a news article is published that points this out and ways one can cut down on it - pretty much by unplugging the devices.

Up to the middle of the decade, standby power was often several watts or even tens of watts per appliance, and amounted typically to 10% of the electrical energy usage of the average household.

 

[Blenton]

He is clearly not talking about standby power.

John, how long does the glow last for? Without knowing what is running the LEDs, its possible that if there's a AC/DC transformer powering them, that when you turn it off, the power supply still has stored energy just enough to provide a small amount of light.

 

[DaveC426913]

He is clearly not talking about standby power.

I am not so convinced.

At first, I thought like you he was talking about LEDs that fade. But really, he can't seriously be wondering if he's paying for that.

 

[Redbelly98]

Just to throw out another possibility, what if these light fixtures are getting "turned off" by turning a dimmer dial or slide down to its minimum setting, which might not be completely cutting the power? (But it might be low enough to get no visible glow from a standard incandescent lamp.) So the lights are not really getting turned off by opening a switch.

 

[John1397]

My Led's are powered off the AC wall switch then thru a a .39 capacitor then bridge rectifier they will burn forever even when switched off and when it is completely dark you get enough light to see. I have read that this is like laying a spool of copper wire under a high voltage transmission line and connecting a bulb and it will burn. It seems to me that the power is jumping across from one hot wire running parallel with the wire coming off the switch. I was just wondering if current is lost or being drawn of the live lines this way if you actually pay for this or is the current or energy that would have been lost anyway?

John

 

[jim hardy]

i'd guess like you, it's capacitive coupling between the two wires going to the switch.


in theory you pay for it, in reality it's probably like 1 / 100 of an amp so way less than a watt.
It won't cost you more than eighty-seven cents per year even if your meter is able to detect it.. just call it a night-light...

Would you post what kind of bulb it is? i'd like one for my bathroom.

 

[John1397]

Just a simple high brightness white led 20000 3.3 volt 25 ma led ordered package of 50 from china wired into c7 to incandescent household bulb sockets really cheap power leave them burn all night and ones with no switch burn all the time.

John

 

[Studiot]

John are you in Europe or North America?

I ask because your LED should not light when disconnected by a switch in NA.
The switch will be single pole and only disconnect the line (phase). I'd lay odds that if you used a double pole switch and disconnected the neutral and line the LED would not light.

In Europe this may happen because the neutral is not grounded and so may float at enough voltage to power an LED. I have seen neutrals light an old fashioned neon.

 

[John1397]

USA

Usually when you switch anything off you assume it is not drawing current or is it? A 100 watt light bulb would never glow when switched off, but then it is to big of a load.

John

 

[jim hardy]

well, think about it.. if the two conductors going to the switch have capacitance between them, as they do in typical houswiring

that capacitance shunts a feeble current around the switch. It may be enough to give an LED a feeble glow .

 

[John1397]

No it is not standby power it is more like a transformer without the iron core.

John

 

[jim hardy]

standby power ?

 

[Deaugh]

I have Led lights in the house ceiling fixtures running on household AC when the are switched off they still give a small amount of light am I paying for this current or is this current that would have been lost anyway?

John

I don't think so as LED lights consume very less power

 

[uart]

well, think about it.. if the two conductors going to the switch have capacitance between them, as they do in typical houswiring

that capacitance shunts a feeble current around the switch. It may be enough to give an LED a feeble glow .

Hi Jim. This is particularly true for wires in a "two way" switch. Here you can often get a fairly long run where the "dead" wire runs directly in parallel (usually in the same cable) with a live wire. My back of the hand calculations suggest that you could get about one nF of coupling there and a corresponding parasitic current of about 50uA. Probably enough to dimly light a high efficiency LED.

 

[John1397]

That's what it is and a 100 watt light bulb running on AC would give off light to, but it is to big of a load to see the light, but do you pay for this type of current or would this type of current have been lost anyway even if there was no light in the socket? Also in house wiring it does not only have to be two way switch just the hot wire coming down to the switch along side the wire going to the light will be close enough.

John

 

[NascentOxygen]

but do you pay for this type of current or would this type of current have been lost anyway even if there was no light in the socket?

These phantom currents all go through your power meter, along with other household current, so potentially will contribute to your power bill. If the stray currents perform real work, then that inevitably gets metered the same as any other V.I.cosɸ component.

It should be possible to establish whether the long run of cable with its capacitive coupling is seen as an overall inductive load or capacitive load. If capacitive, then it will provide a tiny bit of power-factor correction to a normally inductive home circuit. This can be expected to slightly raise your mains voltage and, along with it, your household current, albeit by a miniscule amount, but still it's a rise so reflects as a fractionally higher power bill. However, if the cable proves to be an inductive load, then the converse scenario applies.

Well, that's my take on the situation.

 

[darkwood]

I find this situe more and more common with the introduction of energy saving lamps and what is becomming common place is lights that are switch off flicking at regular intervals, these effect Led's and CFL (Compact flourescents) too, and is usually associated as others have said the parallel running of cables especially in a lighting 2way system where one of the strappers always remains Live!, be it inductive and/or capacitive it seems to charge up the electronics in the lamps till they can strike the lamp then charge is lost and cycle repeats.
Not so common place here in the uk are also illuminated switches that glow when in the off position, this creates a different senerio as it turns the switchwire into a Neutral and a small current flow with go through the lamp giving similar results or even a faint glow.