The first is the drill. My plan is to mount a magnet to the drill head and a reed contact next to it. But this will need debouncing in the software. Is there an option without debounce?
The second is the sine wave that is generated by the motor when it is turned, as it basically turns into a generator. My idea is to use a larger resistor (1k, 10k, something in that region) and a 4,7V Zener. When the motor is turned, 4,7V pulses will ocour over the Zener (I hope). Are there better options?
Why the zener? Why would you every get more than 5V from the sensor?