Chapter 1 PLC overview Exam Revision With Complete Answers Guaranteed For Pass.

Programmable Logic Controller - correct answer an industrial grade computer that is capable of being programmed to perform control functions Real-time System - correct answer the output of the system controlled by the PLC depends on the input conditions Relay logic - correct answer capable of performing relay switching tasks Timing, Counting, Calculating, Comparing, Processing of analog signals - correct answer Tasks in addition to relay switching operations that PLCs are capable of performing. 1. Increased Reliability 2. More flexibility 3. Lower Costs 4. communications capability 5. Faster Response time 6. Easier to troubleshoot - correct answer 6 distinct advantages that PLCs offer over conventional relay-based control systems. 1. Central processing unit or CPU 2. Input/output section 3. power supply 4. programming device - correct answer Parts of a PLC architecture - correct answer can refer to PLC hardware, software or to a combination of both Open architecture design allows the system to be connected easily to devices and programs made by other manufacturers while closed is one whose design is proprietary, making it difficult to connect to other systems. - correct answer Explain difference between open and proprietary PLC architecture 1. Fixed I/Os 2. Modular I/Os - correct answer Two ways in which Inputs/outputs are incorporated into the PLC Fixed I/Os - correct answer typical of small PLCs that come in one package with no separate, removable units. The processor and I/O are packaged together and the I/O terminals will have fixed number of connections built in for inputs and outputs. Advantage: Lower cost Disadvantage: lack of flexibility, if any part in this unit fails, the whole unit has to be replaced. Modular I/Os - correct answer divided by compartments into which separate modules can be plugged, increasing options and the unit's flexibility. Describe how the I/O modules connect to the processor in a modular-type PLC configuration. - correct answer The modules plug into a rack. When a module is slid into the rack, it makes an electrical connection with a series of contacts called the backplane, located at the rear of the rack. The PLC processor is also connected to the backplane and can communicate with all the modules in the rack Basic Modular controller consists of - correct answer 1. rack 2. power supply 3. processor module or CPU 4. input/output 5. operating interface for programming and monitoring Power supply - correct answer supplies DC power to other modules that plug into the rack. Power supply for larger systems - correct answer power to field devices is provided by external AC or DC supplies Power supply for some small micro PLC systems - correct answer the power supply may be used to power field devices Processor or CPU - correct answer brain of the PLC, usually consists of a microprocessor for implementing the logic and controlling the communications among the modules. The processor requires memory for storing user program instructions, numerical values and I/O devices status. Two most common type of PLC programming device - correct answer 1. hand-held units 2. Laptop computers - most commonly used Program - correct answer is a user-developed series of instructions that directs the PLC to execute actions. Programming language - correct answer provides rules for combining the instructions so that they produce the desired actions. Relay Ladder Logic - correct answer is the standard programming language used with PLCs, origin is based on electromechanical relay control. Program graphically represents rungs of contacts, coils, and special instruction blocks. Individual symbols - correct answer represents instructions numbers - correct answer represent the instruction location addresses