Question

Suppose you are to design a new porch light that has 3 modes of operation: OFF, ON continuously, and in the third mode it turns on and off based on its own motion detector. You desire to have this light work with existing house wiring. Describe two different ways that you could make the light work with an existing single-pole single-throw switch. Is one of your methods better than the other? Why? Note this can be done from a block diagram/discussion point of view, you don’t need to know all of the circuit details

Answer 1

Given below is one of the method, You need to use two SPST switch to get three modes of operation. Here is the block diagram

Or you can use a DPDT switch to get three modes of operation.

For a sensor you can use PIR sensor. I had made this circuit.