Towards an Accessible Industry 4.0: Design and Experimental Validation of a Reproducible IIoT Architecture Based on a Compact PLC Platform, Factory I/O, Node-RED and Azure

This paper presents the design and experimental validation of a hybrid architecture for the Industrial Internet of Things (IIoT), based on a Siemens LOGO! v8.4 programmable logic controller (PLC) (Siemens AG, Munich, Germany), Node-RED v3.1.3 (OpenJS Foundation, Wilmington, DE, USA), Microsoft Azure (Microsoft Corporation, Redmond, WA, USA), and Factory I/O v2.5.5 (Real Games Unipessoal Lda, Gondomar, Porto, Portugal). The proposal integrates three main functions—real-time telemetry, structured historical data storage and bidirectional remote control—over an automated tank level process. The architecture was organized into four functional layers: local automation, middleware integration, cloud services and web application. Validation was conducted using five performance metrics: end-to-end latency, remote command latency, successful delivery rate, update rate, and service recovery time. The results confirm the technical feasibility of the proposed architecture for remote monitoring and control, while also identifying the main bottlenecks in the transmission chain. Overall, the study provides an experimental basis for modular and reproducible IIoT solutions with a low adoption barrier and potential applicability to progressive digitalization scenarios in small- and medium-sized enterprises.