In article ,
M.Joshi wrote:
I am trying to design an audible/visual indicator that beeps every 5
minutes when a light switch is turned on.

The complete circuit has to fit behind a light switch plate and so a
transformer cannot be used.

This can't be done unless you have a neutral at the switch position. When
the switch is on there is no potential difference between the terminals
therefore no power source.

Any ideas or pointers would be really useful.

--
*I will always cherish the initial misconceptions I had about you

Dave Plowman London SW
To e-mail, change noise into sound.