Glow in the dark LEDs

[Triassic]

I've fitted a new bedroom light along with three GU9 corn bulbs. The problem is, they glow in the dark after it's switched off and they glow all night.

 

The power goes to the ceiling rose and then to the light switch. It's two way switched, with a switch by the door and a second by the bed. Looking at these, they appear to be wired correctly and the earth is fitted. 

 

Any thoughts on a solution.

[jack]

Did you see this thread: 

Your problem might be something similar.  We have the same problem with some corn bulbs (a term I hadn't seen before!) in our hallway, which I hope, one day, to get around to looking at.

[Temp]

Temporarily replace one LED with a low wattage incandescent. If the LEDs stop glowing then it's most likely coupling between the live and switched live. Nothing really to worry about. Incidentally fitting one incandescent doesn't really solve the problem. It just means the power that is wasted making the LEDs glow dimly when off is wasted in the incandescent instead - it's just not enough to make an incandescent glow. 

[Temp]

Perhaps see the snubber/capacitor solution down here..

http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=28037

 

 

[Triassic]

I've gone for the easy option and fitted halogen bulbs. Sorted!

[daiking]

15 hours ago, Triassic said:

I've gone for the easy option and fitted halogen bulbs. Sorted!

 

I've got some Philips G9 leds, not corn style. No problems. 

[Carrerahill]

This phenomenon can be caused by quite a few issues, it can be if your lighting cable sits near other live cables there can be induced voltage on the line. If two way switched the runs become significantly longer as power goes from switch to switch and back again etc. so more chance of induction. Another cause can be if the earth and neutral is combined or separate at the cable head, for example, if combined small earth leakages can then give the neutral a potential voltage which can then in turn back-feed circuits.

 

Other things can include digital dimmers, which now even includes some rotary dimmers which have microprocessors in them which use the closed circuit through the load to power itself.

 

A capacitor on the lighting circuit can often solve this, usually simply connected in at the back of the switch - easy to get from lighting suppliers and wholesalers but a good quality 400V capacitor with sleeve on the legs would do just fine.

 

 

[jack]

59 minutes ago, Carrerahill said:

A capacitor on the lighting circuit can often solve this, usually simply connected in at the back of the switch - easy to get from lighting suppliers and wholesalers but a good quality 400V capacitor with sleeve on the legs would do just fine.

 

Am I right that the capacitor is just providing a lower impedance path for the induced current? If so, I assume that means it consumes at least the same amount of power this way.  Seems unfortunate that there's no easy way (other than better circuit design) to avoid this continuous energy leak.

[Carrerahill]

36 minutes ago, jack said:

 

Am I right that the capacitor is just providing a lower impedance path for the induced current? If so, I assume that means it consumes at least the same amount of power this way.  Seems unfortunate that there's no easy way (other than better circuit design) to avoid this continuous energy leak.

 

You are thinking more of a resistor which will dissipate energy as heat - yes wasteful. This is also a common 'fix' that was used for dimming LED's but was not ideal as you now have a resistor somewhere getting hot!

 

Anyway, capacitors are connected across the L and N of just about every electronic device or device with a motor. Usually they serve to suppress spikes helping to smooth the power, but can also actually improve the power factor which reduces consumption. Large factories sometimes have a bank of huge capacitors connected across their main incoming supply phases to improve power factor which means machines run more efficiently and therefore reduce consumption - it can make massive savings.

 

So in this circumstance the capacitor sits between line and neutral, the induced voltage is absorbed by the cap, then when the current alternates it empties the previously charged side, so all the cap is doing is really temporarily storing the energy. There is some inefficiency but it is tiny.

[jack]

Ah, makes sense, thanks.