Hi Tom,
No laptop eh, well i'm sure that a suitable circuit could be found instead.
If you asked at the local tech, you never know they might make it for you.
If not don't worry, a few different time intervals selected by a couple of
rotary switches should not be a difficult circuit, but difficulty is subjective
you might be happy with soldering together a bunch of wires and a few relays
with a few components to ring a bell, or sound a buzzer.
Or you might want to make monostables using solid state components,
or you might want to get into PIC's and programming.
Whichever way you want to go, you will need a bell or a buzzer and some sort
of box or carrying case for it.
Some little buzzers can be quite loud for their size, and dont seem to use
much out of the battery.
To my mind, getting the box, the batteries, the buzzer and the two rotary
selectors sorted out, and trying the buzzer to see that its Ok for what you
want,
is more of a problem than sorting out a circuit.
I think a small relay to operate the buzzer, and some discrete transistor
circuitry for the timing and to work the relay.
Batteries?
Whatever seems reasonable to you, so long as it works the buzzer alright
for a reasonable life ... not just when its new.
You say you've done some electronics work in the past,
would you be alright soldering stuff together, maybe on a bit of vero-board ?
Can you read diagrams Ok ?
If so, you shouldn't have a problem, some of these guys are pretty smart.
Regards, John