Task 4 - Sequential Program via Ladder - 25 Marks In considering the task of programming any sequential system, identify and explain briefly the elements that you need to consider in its preparation. In answering this question take into consideration the PLC controlled electro-pneumatic sequence of (A+, B, 2sec, A, B-). "A" and "B" are double acting cylinders controlled via 5/2 double solenoid valves There is a normally open "start" button and a normally closed "stop" button (Electrical) The sequence should only begin to operate when the cylinders are both retracted and the start button has also been activated, it should continue until the stop button is operated, where it shall continue the sequence until the end of its cycle. There is a selection of appropriate proximity sensors placed in the circuit to obtain fully automatic control in your answer: a) Identify the information that you require about the system or machine before programming can commence and list a possible sequence of events a programmer may carry out in developing a sequential program. (6 Marks) b) Then progress to develop the required material to produce a viable program by developing without programming software (paper based) a possible solution to the sequential task above. (14 Marks) Awarded Criteria - Part b Program Functionality Structure Documented program Possible 8 4 2 Totals 14 c) Identify possible methods of documenting the process of a sequential machine and explain briefly how they are used. 15 Marks