Flashing GU10 LED lights

[InMyHO]

In case this is of help to anyone I thought I would document my experience of putting LED bulbs on a two-way (landing light type) circuit.

Having done this a coupe of times now on each occasion I have had the same issue. The circuits previously had halogen GU10 mains voltage spotlights. Replacing these with LED types causes the bulbs to flash when the circuit is turned off. I assume this is thanks to transformer-style induction along the long runs of two-way cable which encases three conductors together - at least one of which is always live even when the circuit is off. While the induced voltage will not be able to deliver any significant current it must be slowly charging a capacitor in the mains-to-extra-low-voltage conversion circuit in the LED bulbs. This circuit then presumably has a go at lighting the bulb and imediately runs out of charge causing the strobe-like flash.

This flashing is annoying to say the least. So my solution has been to add a 1,000,000 ohm resistor in parallel with the bulbs. This prevents the charging effect sufficiently to stop the flashing. Please note that a one megaohm resistor works for a circuit with two bulbs and an approximately 10 metres of cable. A circuit with fewer bulbs or more cable would require a lower value resistor I expect. From my tests I would guess that this resistor is only just low enough to allow the flashing to be supressed. Also remember that the resistor will need to dissipate power and so has to be adequately rated.

I hope this experience may be of use to someone.

 

[Chri5]

Thanks, but the fixes have already been well covered here, which had you used the search facility pre post you would have discovered for yourself.

Personally I've never had the problem, nor seen it where I've been asked to retro fit led lighting in to groups of gu10's.

If I see ELV I pull out the transformers and convert back to 230v.



//www.diynot.com/forums/viewtopic.php?p=1810534#1810534

 

[InMyHO]

Chri5

Thanks very much for taking the time to reply.

Thanks, but the fixes have already been well covered here, which had you used the search facility pre post you would have discovered for yourself.

In fact I had used the search facility to look for any information about flashing LED lights on two-way circuits Chri5 despite your speculative statement above. I did not find anything that had already been posted which is why I sorted out my own solution. Possibly the search was unsuccessful because the phrase "2 way" had been used previously instead of "two way".

I understand your inferred message though Chri5 that if, in future, I learn something which appears to be interesting and should I happen to muse that this might be useful to someone else then I should not succumb to temptation and instead resist any urge to share it in case the topic has been, in some way, discussed before.

Sound implied advice for which I am very grateful.

 

[Taylortwocities]

Please fix a note to the consumer unit documenting your 1MΩ workaround.

Some future electrician will tear his hair out trying to find why there is a "bad" Insulation Resistance reading between live and neutral on that lighting circuit.!

 

[ericmark]

I had also missed bernardgreen's post with the PMR209MB5470M100 unit which combines resistor (100 ohms) and capacitor (0.047µF) to stop this problem.

Over 2 years old and I have noted this problem seems to have reduced so I would assume that manufacturers are now fitting these in their lamps?

I have some 0.58W GU10 LED's which come on dim when on the two way system and I have been wondering if it was worth doing anything about it?

I would guess with more expensive types the problem is catered for by bulb manufacturer and this was mainly as I was using cheap Pound World bulbs.

What I wanted to do was experiment with the cable. As you say one wire always line but also there is an earth wire so the gap is larger and there is a earthed conductor between one core and the rest. So possible swapping cores used may help.

But I am lazy and hoped some one else would do the testing and I could then copy results.

 

[bernardgreen]

From my tests I would guess that this resistor is only just low enough to allow the flashing to be supressed. Also remember that the resistor will need to dissipate power and so has to be adequately rated.

With resistors across mains you MUST also consider the maximum voltage the resistor can withstand. This is the Limiting Element Voltage and in high value resistors can be considerable less than the voltage required to run the resistor at its maximum power rating.

The worst case peak voltage on 230 nominal mains is around 350 volts, LEV on 1/4 watt resistors can be as low as 250 volts

( 230 + 10% ) times 1.41



http://docs-europe.electrocomponents.com/webdocs/0ab1/0900766b80ab1e9d.pdf

 

[InMyHO]

Bernard, Eric and Taylor - thanks very much for that feedback. Really useful, and important, points.

On the issue of which conductors to use my limited experience is that it does not matter - you always get induction - regardless of swapping the conductors around. I have not exhaustively tested this though.

 

[Taylortwocities]

I have found that the issue is found, more often, where there is no effective earth in the cpc of the lighting circuit/strappers.

May be worth a check?

 

[bernardgreen]

Being pedantic.. it is not induction but capacitive coupling that transfers the energy between Live and Switched Live when the switch is OFF.

Induction is magnetic and requires that current is flowing in a conductor to create the alternating magnetic field necessary to induce current in another conductor.

 

[ericmark]

As you say being pedantic if lights are on even if dim then there must be a current flow

 

[bernardgreen]

As you say being pedantic if lights are on even if dim then there must be a current flow

Yes but it is flowing through the "capacitor" formed by the conductors and the insulation between them as if the switch was closed but high impendance. It is not a current created by magnetic induction.

 

[fabnum]

In case this is of help to anyone I thought I would document my experience of putting LED bulbs on a two-way (landing light type) circuit.

Having done this a coupe of times now on each occasion I have had the same issue. The circuits previously had halogen GU10 mains voltage spotlights. Replacing these with LED types causes the bulbs to flash when the circuit is turned off. I assume this is thanks to transformer-style induction along the long runs of two-way cable which encases three conductors together - at least one of which is always live even when the circuit is off. While the induced voltage will not be able to deliver any significant current it must be slowly charging a capacitor in the mains-to-extra-low-voltage conversion circuit in the LED bulbs. This circuit then presumably has a go at lighting the bulb and imediately runs out of charge causing the strobe-like flash.

This flashing is annoying to say the least. So my solution has been to add a 1,000,000 ohm resistor in parallel with the bulbs. This prevents the charging effect sufficiently to stop the flashing. Please note that a one megaohm resistor works for a circuit with two bulbs and an approximately 10 metres of cable. A circuit with fewer bulbs or more cable would require a lower value resistor I expect. From my tests I would guess that this resistor is only just low enough to allow the flashing to be supressed. Also remember that the resistor will need to dissipate power and so has to be adequately rated.

I hope this experience may be of use to someone.

This information has proved helpful. I have just installed new lighting circuits in a house with LED GU10's throughout (cheap Chinese imports I might add not by choice) and have the problem you posted on the up landing two way lighting circuit. It has been driving me mad as the only thing I could think of was the strapper having being squashed at some point while the boarding was carried out and an induced voltage had occurred down the strappers. I have 5 GU10 3.5w LED spots and it only flashes on one of the strappers when switched. One of the lamps actually flashes while the other 4 build up to a very slight level then distinguish once the first one in the line has flashed. I will try your remedy before I remove these cheap lamps for something less irritating.

 

[ericmark]

I found when I swapped from 0.58W to 3W the problem vanished. In fact with a 0.58W and 3W the problem went with both bulbs.

I would guess the B&M Bargain bulbs I used 3 for under £10 have something built into the bulbs.