A Web-based system that includes educational simulations and an intelligent tutoring system has been developed to teach students about programmable logic controllers (PLCs). The system uses Visual Basic, a Microsoft access database, and Macromedia Flash; and is hosted using Microsoft's Internet information services (US). An access database is used to store domain specific knowledge and model student knowledge, and an algorithm asks questions adoptively based on the student model, so that each student receives an individualized practice session. The student interface is easy-to-use and provides detailed feedback about practice question performance and status. Lessons on PLC timer and counter instructions were evaluated by 38 undergraduate manufacturing engineering students. Students made statistically significant learning gains as a result of taking the lessons, and rated them positively in terms of ease of use and understanding, clear objectives, amount of interaction, ability to motivate, relevance, and pace.