On Sat, 06 Oct 2007 03:10:49 +0100, dave
I watched this on the evening news. The face of the reporter was a
picture as they stood under the light and shouted to her husband to
turn the kettle on. The kettle went click and the light went out.
The kettle is the only appliance to do it and it does it in any socket
in the house.
I saw that on the local news too. My theory is that the kettle is probably
the single highest consumption device in the house, at least 2kW and
probably 3kW in this case. The house and the light may be on the same spur
which for whatever reason has a highish reactive impedance back to the local
sub. The street light may be a single one that controls it's on/off cycle
via a light detector on the top - which in turn feeds a switching circuit
for the sodium lamp. The switching circuit probably incorporates a Schmitt
trigger which gives the necessary hysteresis of on/off light level to ignore
lighting variations at dusk/dawn. The regulation/decoupling of the internal
power supply to the Schmitt trigger/switching circuit may not be that good.
Now .... assume light has already switched on, the lady then switches the
kettle on which puts a large transient on her feed line (due to its reactive
impedance) sufficient to couple through the supply/decoupling of the lamps
switching circuit, and enough to push the input voltage to the Schmitt
through its 'off' threshold - lamp goes out.
All pure guesswork but I think a plausible scenario - any other ideas?
In message , EricP
Our porch light is triggered *on* by the light switch in our downstairs
toilet. I have not noticed this happening in daylight.
The installation blurb said something about *blipping* the switch should
bring the porch light on until switched off but I have never succeeded
in doing this.
Line transient as has been said elsewhere.
In article ,
That article is self contradictory.
Some discharge lamps can be very sensitive to voltage fluctuations,
particularly near their end of life. The kettle could be causing a
small drop in mains voltage.
And you trust them not to have fixed it? You don't see the light and
switch in the same shot, though I'll admit it doesn't look "a fix" unless
the reporter is a very good actor. The standard of journalism in the
written story is well down as well:
"Just when I go to make a cup of tea in the morning, I switch
First para indicates that the street lights (plural) go off, but the
online video refers only to a single light and only shows one light.
Second half of the second para contradicts the first para, street light(s)
coming on rather than going off. It is a quote but surely any half decent
journo would have spotted the error that destroys the story FFS!.
Bit of a dopey electricity engineer if he couldn't trace what was
happening. I guess he just wanted out of there with the TV news crew
The house is on the same phase as the street lights (I bet it's a fairly
small street). There is a bad connection in the main splitter box feeding
the street on that phase.
There's no mention as to whether the effect happens with other houses on
the street, so she may be in the only house on that phase.
Kettle = volt drop across bad connection = drop out on discharge lamps
I don't know if it's still there, but I used to see houses in Liverpool
with single phase wiring along the outside of a row of terraces (near
Everton FC). There was a tap off the pair for each house and another tap
to feed the street lights fixed to the fronts of the houses. Not the best
sort of installation... :-) The volt drop at the end house must have
been horrendous when the others put their kettles on.
Tim Lamb explained on 06/10/2007 :
They usually work roughly as follows....
A quick off then back on makes the light stay on until it is reset, or
until the next period of daylight.
To reset back to normal operation, turn it off and leave it off for
more than 10 seconds, then turn it back on.
Reminds me of the psychic dog...
This story was related by Pat Routledge of Winnepeg, Ontrario about a
repair call he handled while living in England.
It's common practice in England to ring a telephone by signaling extra
voltage across one side of the two wire circuit and ground (earth in
England). When the subscriber answers the phone, it switches to the
two wire circuit for the conversation. This method allows two parties
on the same line to be signalled without disturbing each other.
Anyway, an elderly lady with several pets called to say that her
telephone failed to ring when her friends called; and that on the few
occasions when it did ring her dog always barked first. Pat proceeded
to the scene, curious to see this psychic dog.
He climbed a nearby telephone pole, hooked in his test set, and dialed
the subscriber's house. The phone didn't ring. He tried again. The
dog barked loudly, followed by a ringing telephone.
Climbing down from the pole, Pat found:
a. A dog was tied to the telephone system's ground post via an iron
chain and collar.
b. The dog was receiving 90 volts of signalling current.
c. After several such jolts, the dog would start barking and urinating
on the ground.
d. The wet ground now completed the circuit and the phone would ring.
Which shows that you that some problems can be fixed by just pissing
Its a modern system controlled by rf signaling on the mains.
The kettle interferes with it.
Solution.. buy her a new kettle and send the old one to the manufacturers of
the control system to fix the system.
Hmm. Pee completing the circuit is an elaboration to this urban legend
that I hadn't heard before. The usual version has the lady reporting
that her phone no longer rang but that she always knew when somebody was
calling because her dog barked.