Mains 'problem' with flashing light globes when switched off.

Just a quick query, as I imagine somebody here will know what's going on here:

I have a hallway with two light fittings and two switches at both ends of the hallway. I had a 4w LED globe in one fitting and none in the other fitting. Before that, a single CFL globe. Worked fine.

Today I replaced the 4w LED globe with a 2w LED globe. This 2w globe flashes every few seconds, even though it is turned off at the switch. If I put another globe in the other empty light fitting, the flashing stops.

What is exactly going on here and is there any way I can stop it (aside from not using this globe or using two of them)? I have a friend with the same 'problem', only his does it with a CFL.


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Looks like your switch allows a small leakage current going to the LED lamp, is rectified, slowly charges the capacitor of the LED driver until the voltage is high enough to switch on the LED lamp.

As this leakage current is very low, there is only very little current available, so the driver's capacitor will immediately discharge, switching the LED off very quickly.

This repeats continuously and causes the flashing of the LED.

Putting a load in parallel of the LED (when you put another globe in the other empty light fitting) prevents the voltage to build up, because from a certain, quite low, level of voltage all the leakage current is going through that secondary parallel load.

Maybe some ants took residence inside the switch' enclosure?

If not, maybe replacing the switch will solve the 'problem', or putting a quite large resistor parallel to the LED lamp. Think MOhms...

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joe hey

it's current flowing through the caqpacitance in the wiring to, and between the switches.

connect a 100nF (or larger) "X2" rated capacitor in parallel with the lamp sockets. The best location to install it is somewhere other than at one of the sockets, as, if someone installs an old-fashoned bulb it will get really hot at the lamp socket.

Jaycar electronics CAT. NO. RG5236

OTOH this instructable used a 12OK resustor

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but you'd want ones that are ok with 250V AC, and flameproof and jaycar doesn't promise that on their resistors..

umop apisdn 

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Reply to
Jasen Betts

Many thanks Joe, will keep that in mind, might be easier if I change to another globe for the time being :)

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Thanks Jasen, I'll keep the above in mind but am a bit concerned about the heat you mention (and potential insurance issues), I might simply change globes again for the time being.

I'm assuming that, since it is only some but not all globes that do this, that some globes are built more cheaply than others and lack the circuitry to avoid the flashing problem? I've done a bit of a search just before, and most people point to dimmer or illuminated switches, which I have neither of. The capacitance you mention makes more sense in my case.

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