Mains lighting with no mains - not quite boaty

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richardabeattie

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The following defies logic but has happened. How?

A pendant bedroom light fitting with a modern low energy coiled lamp, switched at the door and over the bed. It's worked fine for years.

But last week when I went to bed and turned the light off there was a low intensity pulse of light every 8 secs or so . Oh I thought - perhaps there is a capicitor in there somewhere so I removed the lamp to let it discharge. Next morning I put it back and the flash started up again though barely visible in daylight. So I thought maybe one or both switches is allowing a small current through - just enough to tickle the bulb into brief action. So I changed both switches. Still flashing. So I put in a new lamp of the same type. Problem solved. Then I put the apparently defective lamp into a table lamp on a different circuit and it did not flash when off.

Poltergeist? Lamp being activated by the Weak Nuclear Force - but only in the bedroom?

Grateful for any clues as to what was going on!
 
Yes, I've noticed that too and I don't think either of the explanations on Wiki apply.

In our case it happens with the later generation Philips lamps that come on instantly. It's my belief the circuitry in the lamp does this to maintain the ionisation in the tubes necessary for "instant on".
 
richardabeattie said:
The following defies logic but has happened. How?

A pendant bedroom light fitting with a modern low energy coiled lamp, switched at the door and over the bed. It's worked fine for years.

But last week when I went to bed and turned the light off there was a low intensity pulse of light every 8 secs or so . Oh I thought - perhaps there is a capicitor in there somewhere so I removed the lamp to let it discharge. Next morning I put it back and the flash started up again though barely visible in daylight. So I thought maybe one or both switches is allowing a small current through - just enough to tickle the bulb into brief action. So I changed both switches. Still flashing. So I put in a new lamp of the same type. Problem solved. Then I put the apparently defective lamp into a table lamp on a different circuit and it did not flash when off.

Poltergeist? Lamp being activated by the Weak Nuclear Force - but only in the bedroom?

Grateful for any clues as to what was going on!
Click to expand...

is this not best suited to scuttlebutt or the lounge :eek:
 
let's hope it isn't strong nuclear!

richardabeattie said:
...Lamp being activated by the Weak Nuclear Force...
Click to expand...
Well, since weak nuclear theory has now been combined with EM, this could be close! Seriously 'tho, it could be a high electro-magnetic field.

There is unlikely to be enough energy stored in the thing, and lamps are usually just neutral + live (so no earth wire), so when the live side is o.c. it really must be off. So 3 possibilties strike me:

(i) a radio transmitter. Only affects the bedroom because of the length and orientation/path of the wiring.
OR
(ii) a leak past the mains switch. This could be from a tiny lamp, possibly neon, across the the switch designed to illuminate the switch (so you can find it) when the light is off. Damn dangerous, and unlikely to be the case but who knows what a previous owner might have done (a bit like boats really)
OR
(iii) the unique wiring in your section of the National Grid is a perfect high-gain antenna tuned to a pulsar from another galaxy.

I've known a neon tube to glow when a neighbour transmitted on HF, so that might do it. Not sure what it would be doing every 8 secs (nothing I can think of from GSM, UMTS, LTE or Tetra has that period).

PS: I don't really think it's (iii)!
 
The intensity is so low it can only be seen using peripheral vision.

Radar is certainly a possibility as I first noticed it in Farnborough, though we were a couple of miles from the airfield and not line of sight. Haven't really checked it out recently as it didn't seem that important ... ... ...
 
fwiw, my low energy bulbs seem to do that just before they 'go'. maybe they 'go' because they're doing that.... i don't know....

laura :)
 
richardabeattie said:
The following defies logic but has happened. How?

A pendant bedroom light fitting with a modern low energy coiled lamp, switched at the door and over the bed. It's worked fine for years.

But last week when I went to bed and turned the light off there was a low intensity pulse of light every 8 secs or so . Oh I thought - perhaps there is a capicitor in there somewhere so I removed the lamp to let it discharge. Next morning I put it back and the flash started up again though barely visible in daylight. So I thought maybe one or both switches is allowing a small current through - just enough to tickle the bulb into brief action. So I changed both switches. Still flashing. So I put in a new lamp of the same type. Problem solved. Then I put the apparently defective lamp into a table lamp on a different circuit and it did not flash when off.

Poltergeist? Lamp being activated by the Weak Nuclear Force - but only in the bedroom?

Grateful for any clues as to what was going on!
Click to expand...

Common problem.

Some lamps are more sensitive than others.

It is the capacitance in the wiring between the the lamp & the switch, which is why it does not do it in the table lamp.

Table lamp = switch is in the fitting, short wire between the switch & the lamp.

Pendant lamp, with the wiring to a loop in ceiling rose, L N & E are in the ceiling rose, a twin & earth from there to the first switch, then 3 core & earth from the 1st switch to the 2nd, the switch wire (connected to the lamp) is running next to a live all the way from the ceiling rose to the 2nd switch, longer cable = more capacitance.

Sounds like there is just enough to charge up the ballast in the lamp to make it flash once in a while.

Some ballasts have a high value 'bleed off' resistor within them, it is possible this has failed in this particular lamp.
 
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