In message , Frank Erskine
writes
On Thu, 17 Jun 2010 18:29:28 +0100, Timothy Murphy
wrote:

My small city garden has a standard Victorian railing
on the street, with the gate as part of the railing.
A few days ago someone came in the garden and stole
a (locked) bike.

This made me wonder if there is any simple way
to make a bell ring when the gate is opened?

Fit a padlock or something similar to the gate, and a nelectric bell
for bona fide callers.

If you do want a "gate-operated" bell, I'd suggest a reed switch and
magnet rather than a microswitch from the point of view of weathering.
Hamlin do enclosed-type reed switches (e.g 59065-020) and associated
magnets; it should be trivial to knock up a suitable circuit (well,
sub O-level) to ring a bell as you wish.

Also, is there a standard spring which will
keep the gate closed?

Yes. A standard torsion gate spring is easy to fit (and only a bit
fiddlier to adjust!)

Just think of the useful energy in that


--
geoff