This is a custom ultrasonic level detector I designed to give me a reading of how many cans I have left in my vintage Coke machine.

It was designed in Fusion 360, with 4 printed parts. Three parts make up the housing and one holds an ultrasonic sensor inside the machine to take the readings. The three parts of the housing snap and slide together without the need for fasteners. The base and front face also hold the IC boards in place without tools or fasteners.

The full write-up is on Instructables.com, user ChrisN219. https://www.instructables.com/id/Coke-Machine-Can-Level-Detector/

The second version activates the display screen using another ultrasonic sensor to detect a person walking up to the machine instead of using a push button.

The device is driven by an Arduino Nano, a couple HC-SR04 ultrasonic sensors and an SSD1306 style 0.96 LCD screen. It also uses a power adapter connector I pulled out of a broken device, so that I can power it using the USB connector on the Nano, or using a 12V DC adapter.