Spill-O-Not: A contactless material level indicator for visually impaired users

Abstract The danger of incorrect pouring of hot or sticky liquids is a constant daily safety threat for 295 million visually impaired individuals around the world. Conventional dip-probe liquid level sensors have metal contacts that are exposed to corrosion and require frequent cleaning. As a result, conventional dip-probe liquid level sensors often require replacement and incur recurring maintenance costs, which reduces the long-term usability and safety of these sensors for visually impaired users. This paper presents Spill-O-Not, a portable device that utilizes a miniature Light Detection and Ranging (LiDAR) Time of Flight (ToF) sensor and integrated audio feedback to alert users when the material reaches an adjustable fill height. The fact that the sensor is contactless and allows Spill-O-Not to sit on top of the rim of the container represents a significant improvement over traditional contact-based liquid level indicators. In the 48 controlled laboratory trials using various conductive, non-conductive, and particulate materials, Spill-O-Not prevented all overflows, while maintaining a mean absolute percentage error of liquid level measurement accuracy 4.7%. The authors believe that the demonstrated low-cost sensing technology and inclusive design can significantly improve the safety and independence of millions of visually impaired users.