Welcome to the list James (one other post in April I see).

A comment on message tags.
Proper format is    [TAG]    or optionally  [TAG]:  but the colon is now
optional (used to be needed).

Putting a colon inside the ] makes it, I think, an incorrect tag.

     ise [EE] or [EE]:  or even [EE]::: :-)

  BUT NOT eg  [EE:]        etc

______________

You can feed mains power to your 5V device via a separate feed (series
capacitor as Joe suggested) or a transformer etc.

If 5V current is low compared to load operating current you can operate it
in series "always on" but this may cause regulatory issues and safety issue=
s
of always having main present must be addressed.

Result depends on cct but say cct stabilises with 5Vacross load and balance
of Vmains across bulb.

   At say 1 mA standby load the bulb will "see" 110 mW and a normal mains
bulb (say 60W) would not show any sort of glow.
At 10 mA ~=3D 1 Watt you MAY get some glow - especially in a very dark room=
..
You'll need to experiment to see what max current suits.


          Russell

..





    Russell

On 17 June 2011 14:19, james tornes <james.tornes@gmail.com> wrote:

> I have an interesting problem. I have a mains circuit that looks like thi=
s:
>
> mains---110VAC--+ on/off switch +-------------------+ load
> +----------mains return
>
> The load is a regular incandescent light. I need to insert a 5V device
> in series with the switch. The problem is that when the switch is off,
> then the device also goes off. I have heard that leakage current could
> be a way to still have a mostly functional switch and still be able to
> provide power to the 5V device. But I haven't been able to find any
> designs/circuits that show this. Anyone have any advice?
>
> Jim
> --
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