Objectives: After reading this chapter, the reader should be able to do the following: Describe and configure Arduino PLC programming software and related tools; List and describe five different methods of programming a PLC within the IEC IEC61131–3 standard; Summarize the fundamental concepts of Ladder Logic (LD) PLC programming; Describe library instructions within the Arduino PLC IDE; and Employ the Arduino PLC IDE to write, compile, and execute ladder logic programs for the Opta series of PLCs.