In our kitchen, the light that falls on the counter is blocked by the kitchen cabinets. It would be nice to have some light when preparing food, but often when you need light, your hands are dirty. I came up with the idea of running a strip of LEDs under the cabinets and being able to control them by waving your hand under the cabinet to turn them on. You can adjust the brightness by moving your hand down from just under the cabinet to counter level to control brightness based on the distance from the cabinet.
I am using an ultrasonic range sensor to determine the hand distance between the cabinet and the counter. I don’t want to run the sensor all the time because, even though we can’t hear the 40kHz chirp, I imagine the dogs and bird (our pets) can hear it. Additionally, I imagine there is a limited lifetime on the sensor. So I added a pyroelectric infrared (PIR) sensor that will only activate the ranging when it senses movement around the counter.