Well I always figured that if the interface for a microwave timer is touted as being the yardstick for a quality timer, why not simply use a microwave timer. You'll can save some cash and do your bit for recycling at the same time.
If I am lucky, I can make a trip down to my local dump and pick up a microwave oven for nothing, otherwise I can drive to the city dump and buy one for $5. You may even have an old one sitting in your basement, or have a friend who does.
If you decide to build one of these yourself, you will need to have it checked by a qualified electrician before connecting it to any mains electrical supply.
What is this project useful for?
Most applications where you need to run a mains powered device for a specific period of time and then have it automatically turn off. Most microwave timers will run for a maximum of 1 hour 40 minutes (99 minutes 99 seconds). There are probably dozens of potential applications.
Update: I have since discovered that this timer can be programmed to run for anything up to 3 hours and 20 minutes. By utilising the "cook time" feature, 2 separate time periods can be entered and the machine adds them together.
What you will need for this project:
1: A disused microwave oven
2: Mains input and output sockets
3: An enclosure for your timer
4: screws/bolts to hold everything together.
5: Electricians wire nut to connect the electrical wires.
6: Common sense and caution regarding electricity
Tools I've used for the project: (you may get by with less)
Dremel style handpiece
Dremel cutting disc attachment