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On Jun 25, 8:03 am, Seán O'Leathlóbhair wrote:
I am not sure if this is an appropriate group for this question. If
not, please suggest a better one.

I have a light in the house which I have wanted to switch to a low
energy bulb for a long time. The hold up was that I needed a very
small bulb. At last, I have found a small enough bulb but something
odd occurred as soon as I put it in.

When it is switched on, it works as expected.

When it is switched off, it blinks every few seconds. So, I guess
that there must be a problem with the switch If it is passing nothing
then it would seem impossible for the bulb to do anything. I did not
notice any problem with the previous incandescent bulb but I guess
that if the switch is leaking a tiny amount, the filament would glow
too little to be seen.

I have a few questions:

What is going on? Is a tiny current leaking, building up a charge in
a capacitor somewhere until a sufficient voltage builds up to spark in
the bulb and discharge the capacitor, and then the cycle repeats.

Is it safe?

Will it wear out the bulb very fast?

Is it likely to be enough to replace the switch? (Actually three
switches can turn this bulb on and off).

Might I have to replace the wiring? (Much harder than just replacing
the switches)

--
Seán Ó Leathlóbhair

| You have a more complicated circuit than you think. If you have 3
| switches, each capable of turning the lamp on and off irrespective of
| the positions of the other two switches, then the switches are not
| directly connected to the lamp. The switches are connected to a (-n
| electromechanical) relay or a solid-state relay. The relay provides
| power to the lamp...the switches control the relay. I suspect leakage
| somewhere in wiring between the switch(s) and the relay...which, if
| solid-state, may require only a few milliamps to trip the relay.
| Could also be that the control relay is defective somehow...

Don't think so. The first course on lighting installation I learned about
crossswitches already. They could be used to turn on and off a lamp from one
to three or more places. Effectively they are dpdt switches. You can of
course use it for spst or simply on/off switching. Next possibility is using
it for spdt like the well known two switches landing light. When you need
more switches the dpdt switches are required.

o--+----+ o----+----+----o
+--o--__ | +-o--__ | | __--o--+
hot | o--)--+ o--+-)--+-)----o |
--+ | | | | | | | .-.
| | | | | | | +--( X )---
| o--+ | o--+ | | +---o | '-' neutral
+--o--__ +---o--__ | | __--o---+
o-----+ o----+ +-----o

Three switch landing light using dpdt switches. The right and left switches
are wired for spdt.


o-----+ o-----+
+--o--__ | +-o--__ |
hot o--+ o--+--)--+ o--+--)-------o .-. neutral
--o--__ | | | | __--o--( X )---
o--+ o--+ | o--+ +-------o '-'
spdt +--o--__ +----o--__ | spdt
o-----+ o-----+
dpdt dpdt

Four switch landing light. You can repeat the dpdt- or crosswitch as often
as you need.

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