These hooks have a small sensor, which sense that an item has been taken off the hook (or placed back) and a micro-controller to send an event to digital signage system. Each hook has it’s own ID, so the digital signage system will know exactly what item the customer chose and display an information about this item.
The sensor contains a very tiny invisible laser source, and a matching sensor. Since it uses a very narrow light source, it is good for determining line crossing by an object or a person. Unlike sonars that bounce ultrasonic waves, the ‘cone’ of sensing is very narrow. Unlike IR sensors that try to measure the amount of light bounced, the laser is much more precise. This sensor can handle about 5cm to 1.2m distance.
It is connected to a micro-controller, which measures the signal and then transfers the event to the digital signage system.