Low Energy Lamps Flashing After Switchoff.

[Stuart B]

My bedroom ceiling light ,which is controlled by three wall switches,is a Philips 100 Watt Low Energy type .The box calls it "Genie" .It's the kind that has a bulky part just above the bayonet fitting and looks like four flourescent tubes in "U" shapes . After I went to bed last night I knocked over a cup of tea and ,using the wall switch above my bed switched on the light .After cleaning up the spillage I switched the light off and then saw what I thought was a lash of lightning but when I looked up I realised it was the ceiling light flashing .....about once every three seconds or so .I then switched the light on again but put it off using one of the other wall switches .Again the light flashed but at a lower intensity. It stopped after about a half minute or so.

Anyone else experienced this .Do thses lamps hold energy after switchoff that needs to be dissapated ?. I'm very curious as to why this happened .

Stuart

[Nick]

Its the same process that makes a neon flash with a high enough value series resistor - the strike voltage is higher than the run voltage, so as the voltage builds it strikes, runs for a few milliseconds as the voltage decays then extinguishes, then start all over again..

Just a guess

Nick

[Chip]

On Sat, 24 Nov 2007 11:35:49 +0000,it is alleged that Stuart B spake thusly in uk.d-i-y:

Nick's answer upthread is mostly correct, but it's not entirely resistance (although a slightly 'leaky' switch would cause it for sure), it's most likely cable capacitance. AC can pass through a capacitor, the 2 (or more) wires in the switch cable act as a low value capacitor.

The fact it's switched from 3 positions adds greatly to the effect, as you have more length of parallel cable. This is also supported by the flash rate being different/intensity being different depending on which switch is used, as it alters the configuration of live/not-live wires.

It's interesting that it's a Philips lamp, my better half's flat had the same issue with one. After much poking around with a meter, I found that simply switching to a "cheap given away by the electricity company" CFL solved the issue. Other alternatives are available, including low wattage normal lamps in parallel, just putting up with it, etc.