IoT–Integrated Optical Thickness Sensor with LED Light Source

This research investigates the development of a cost–effective IoT–integrated optical thickness sensor utilizing an LED light source for product quality monitoring. The primary objective is to assess the feasibility of employing a simple optical device to measure the thickness and color of transparent flat surfaces. The methodology involves an RGB LED source that emits light toward the transparent plastic sheet, with the transmitted light being collected by a photodetector and sent to a NODEMCU through an operational amplifier. The LED–emitted rays are partially reflected by the material layer, while the remainder of the light is either absorbed or transmitted depending on the material properties. The optical sensor is connected to the Blynk application to enable IoT capabilities, allowing for the collection of 200 data points per measurement. Experimental results demonstrated that the sensor achieved a maximum sensitivity of 1.44 V/mm and a linearity of 95.49% when measuring a transparent green plastic sheet with a green LED light source. This work underscores the potential of integrating optical sensing technology with IoT solutions to enhance quality control processes in various industries.