Programmable Logic Controller (PLC) is a digital computer for automation of process such as control of instruments in industries. It uses a programmable memory to store instructions and specific functions that include ON/OFF control, timing, counting, sequencing, arithmetic, and data handling. The basic parts include processor, input/output devices, memory unit, programming panel and power supply. Static Application Panels are designed to produce input and output from the PLC. Early electrical control systems were composed of mainly relays and switches. A relay, or contactor, is an electromagnetic device composed of a frame (or core) with an electromagnet coil and contacts with some movable and some fixed parts. Due to its disadvantages like chattering, complicated wiring and less flexibility relays are replaced by PLC. The SAP panels and ladder programmes were developed for automatic bottle filling machine, water level controller, logic gates and counter and comparator. Ladder programme is downloaded into PLC and verified with SAP model. According to the condition and comments provided in the ladder programme the SAP model works, if any deviation in the comments provided and this can be modified in the ladder diagram. This paper explain about the PLC, SAP model and ladder diagram designed for bottle filling machine, water level controller, logic gates and counter and comparator.