Hi!

Anyone have a foolproof system for warning us or setting off
an alarm to warn us of the breakin?

Nothing is going to be foolproof. If someone wants to steal from the vending
machine, they will do so.

That said, I'd think a few things might help...good lighting in the area
where the machines are might do more than you'd think for security. Moving
them to a frequently occupied area might also produce an improvement...it's
simply harder for a thief to work at compromising the machine in good
lighting and with a crowd present.

If that's not enough, have you considered restricting access to the machines
in some way? An iron bar cage around them with openings only big enough to
work the machine and retrieve the product it vends might work. This could
have a gate that opens and is heavily protected, or it might open from the
back via a more conventional locked door. I've seen this done before with
vending machines in public areas, and the formation of the bars can be
decorative while remaining functional.

On the electronic protection front, a magnetic action or reed switch could
be used to sound an alarm when the machine is forced open. Of course, one
would have to turn the alarm off before filling the machine, but that's
likely with any alarm solution.

As far as your camera problem, putting the camera out of reach or where it
can't be easily seen might help...if it's possible to do this. There are
cameras available that look like everyday objects, such as smoke alarms or
ceiling mounted speaker systems. Sometimes the object they're built into is
also functional.

William