Development and testing of a cost-effective vision system for programmable logic controllers monitoring

Programmable Logic Controllers (PLCs) are used extensively in manufacturing to control and manage processes. The data from PLC systems can provide useful information for manufacturers looking to model processes, analyse performance and identify bot-tlenecks. However, real-time data collection in older PLCs requires invasive changes to the existing PLC or a complete replacement for a new smart connected PLC; this intrusive work leads to disruption in production and requires specialist knowledge. This paper presents a low-cost, non-invasive approach to collecting PLC data. It uses off-the-shelf components and open-source software. A camera is positioned in front of the PLC I/O module panel. The indicator lights’ display is recorded and processed to extract state information. The system has been evaluated in the lab under different PLC running frequencies and various lighting conditions. This innovative approach of using a vision system to collect PLC data is shown to be feasible and robust enough for use in manufacturing environments.