You have been asked to describe the selection criteria for 3 different PLC applications. To do this:
a. Identify 3 real PLCs and 3 applications (1 for each PLC) that may be suitable for the following:
• A unitary PLC in a building
• A modular PLC in a factory
• A rack-mounted PLC in a factory
b. Estimate the quantities and types I/O devices required for each system to work e.g. 5 off 24v digital proximity switches, etc.
c. Finally illustrate your PLC requirements on a block diagram to show that the I/O can all be connected to the selected PLC, which might mean that you show several I/O modules.

Checklist of evidence required: 1a an image or reference as evidence of the real PLCs. Typical applications include auto door, heating control and conveyor systems. 1b. The estimate of quantities and types of I/O’s for each application should be supported by reason why you think these required. (2-300 words).1c. the 3 PLC block diagrams should match the specific applications you identify in 1a. Multiple I/O’s of the same type can be drawn as 1 line e.g. 1 line for: 5 off 24v digital proximity switches.