james tornes wrote:

> I have an interesting problem. I have a mains circuit that looks like
> this:
>=20
> mains---110VAC--+ on/off switch +---+ load +---mains return
>=20
> 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.=20

It seems nobody of the other responders really picked up on this.=20

> 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.=20

If you want to work with some "always on" current (which is what all the
others have described), your device can't be /only/ in series with the
switch. So you probably have to decide whether this is a hard
requirement, or whether you can connect your device to both ends of the
switch, essentially making it a three-pole connection:

110VAC--+ on/off switch +-(device)--+ load +---mains return
        |                    |
        +--------------------+

Gerhard
--=20
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