Abstract: In a liquid level monitor for use with a liquid container of a liquid-consuming device, a light source transmits a light beam into the liquid container at a non-normal angle of incidence respective to a wall of the liquid container. A photodetector is positioned in the path of one of (i) the light beam after passing through the liquid container when the light beam is not refracted by liquid in the liquid container and (ii) the light beam after passing through the liquid container when the light beam is refracted by liquid in the liquid container. In another approach, the sensor for detecting empty includes a vibrator and a vibration sensor, and an electronic processor is programmed to determine whether the liquid container is empty of liquid based on the detected vibration of the liquid container.

Abstract: In a liquid level monitor for use with a liquid container of a liquid-consuming device, a light source transmits a light beam into the liquid container at a non-normal angle of incidence respective to a wall of the liquid container. A photodetector is positioned in the path of one of (i) the light beam after passing through the liquid container when the light beam is not refracted by liquid in the liquid container and (ii) the light beam after passing through the liquid container when the light beam is refracted by liquid in the liquid container. In another approach, the sensor for detecting empty includes a vibrator and a vibration sensor, and an electronic processor is programmed to determine whether the liquid container is empty of liquid based on the detected vibration of the liquid container.

Abstract: An air freshener includes an electrically powered fragrance dispenser having a connector configured to connect with a fragrance container. A light source transmits a light beam into the fragrance container at a non-normal angle of incidence respective to a wall of the fragrance container, and a photodetector is positioned in the path of one of (i) the light beam after passing through the fragrance container when the light beam is not refracted by fragrance liquid in the fragrance container and (ii) the light beam after passing through the fragrance container when the light beam is refracted by fragrance liquid in the fragrance container. In another approach, the sensor for detecting empty includes a vibrator and a vibration sensor, and an electronic processor is programmed to determine whether the fragrance container is empty of fragrance liquid based on the detected vibration of the fragrance container.