A Low Cost FBG Based Online Weight Monitoring System

Fiber Bragg Gratings (FBGs) are known for their high sensitivity towards strain and temperature variation. In this manuscript, the strain sensing property of FBG is utilized and explored for measuring weight using a common binocular shaped cantilever type load cell. The shift in Bragg wavelength due to load application is converted into optical power variation using edge filter detection technique. Furthermore, change in optical power is converted into voltage variation and is feed to the Raspberry Pi via analog to digital converter (ADC ADS1115) for real-time and continuous online monitoring of weights. The optical load cell has shown linear response for applied weight up to 8kg. Mechanical properties of optical load cell such as nonlinearity, hysteresis, repeatability, creep and safe over load are studied in detail. Message Queuing Telemetry Transport (MQTT) protocol is used to send data from Raspberry Pi to IoT cloud. The system has achieved resolution of 20g with error of ± 50g.