Arduino board to control microwave oven? So I've taken apart an old microwave oven with a touch-sensitive LCD screen. I understand that I could die from playing around with this, so I've disconnected the high-voltage transformer and the magnetron. I'm also not going to remove any of the safety switches like the door switch. My question is, how is the microwave controlled? I'm thinking there is a computer chip somewhere in the circuit, and I'm looking to replace it with an Arduino board plus some extras, like AC relays and such. I'm curious as to how the microwave oven controls its functions, like power level, cooking time, and the beeping. Any advise as to how I could get started interfacing? 

Is the power level controlled by PWM by any chance? Can you PWM alternating current?
It's pretty much all proprietary. It can be done, but you'd have to replace all the circuitry with the Arduino, interfacing with the existing magnetic and mechanical devices and doing everything in your own code.

Power level is controlled by PWM, but it's extremely low frequency PWM, on the order of 0.05Hz (20s period). That's why there are two different sounds that come from the microwave when it's not at full power; one when the magnetron is active, and one when it is off.