On Thu, 29 Dec 2005 09:02:49 +0000 (GMT), "Dave Plowman (News)"
put finger to keyboard and composed:

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.

What about using a dimmer switch set to about 90% duty cycle? The
circuit could grab some power during the 10% off time.

- Franc Zabkar
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