led bulbs flashing

[daz1963]

hi guys. just fit a load of kosnic 5watt leds in a kitchen. look great really bright but. as its a big kitchen they are on a 2 way switch.when switched off the last led in the circuit starts to pulse. take it out and the one next to it starts to pulse. tried changing the strappers round to no avail. rung kosnic and it seems to be a common problem,pretty muck like the old cpfs we used to see in hallways that flashed on 2 way switching. only suggestion he could give was to fit a snubber or a contact suppressor. did a quick google and not realy sure how to combine one of these into the circuit. my question is has anyone fitted one of these? if so how and did it work?
many thanks in advance.daz...

 

[mogga]

wasnt there another thread with nearly the same problem? try searching it was quiet recent

 

[Silly Sausage]

http://www.electriciansforums.net/e...-flickering-leds-whassup-guys.html#post369884

but the problem was unresolved...

 

[bob22]

http://www.electriciansforums.net/e...e-voltage-readings-has-anyone-else-tried.html am not sure,not done this myself but would fitting a resistor parallel to the first light help to dissapate the voltage in the floating wire back to neutral.

 

[MarkieSparkie]

Hi Daz, This phenomenon is caused by the final circuit cable capacitance. It is more common in conventionally wired two way and intermediate switching circuits due to the wide spread use of 3+E cable and the extra parallel capacitance that creates.
The GU10 mains LED lamp is essentially a number of LEDs driven by a constant current driver powered by a mains rectifier and smoothing capacitor.
Even though the live feed to the LED lamp is switched OFF the cable capacitance allows leakage current to flow to the lamp slowly charging the smoothing capacitor in the lamp until the potential is sufficient for the constant current driver to "fire" the LEDs. This discharges the smoothing capacitor, the constant current driver stops, the LEDs extinguish and the process of charging starts again ... if conditions are suitable this continues indefinitely.
A simple solution is to permanently discharge the cable capacitance by wiring two 160K ohm, 1/4W, resistors rated at >=250V, in series across the lamp holder terminals. Do not try to use a single 330K ohm resistor because this may fail due to voltage breakdown.
If this solution is implemented a notice should be placed at the DB stating which final circuits are effected and which lamp holders have been modified and how.
A conventional GLS filament lamp doesn't suffer this problem because the filament is permanently loading the cable capacitance and any acquired charge is unable to overcome the thermal inertia.

 

[daz1963]

thanks mark. would you wire that resistor to the last lamp in the circuit which is the only one flashing or all of them? many thanks for your informative answer...