Term
| Discrete Process Control Systems |
|
Definition
| Deal with parameters and variables that change at discrete moments in time |
|
|
Term
| Two Principle Industrial Controllers used to Implement Discrete Control |
|
Definition
Programmable Logic Controllers (PLCs)
Personal Computers (PCs) |
|
|
Term
| Examples of Binary Sensors and Actuators used in Discrete Control |
|
Definition
Limit Switch
Photo Detector
Pushbutton Switch
Timer
Control Relay
Circuit Breaker |
|
|
Term
| What is the purpose of the controller? |
|
Definition
| to coordinate the various actions of the physical system |
|
|
Term
| Two categories of Discrete Process Control |
|
Definition
Logic Control - EVENT DRIVEN
Sequencing - TIME DRIVEN
*both are referred to as SWITCHING SYSTEMS* |
|
|
Term
|
Definition
a.k.a combinational logic control
RULES: (test question)
- determined by values of control inputs
- has no memory & doesn't consider previous input signals to determine output signals
- no operating characteristics that perform directly as a function of time
Elements: AND, OR, and NOT
inputs determine outputs
|
|
|
Term
| Values of Logical Control |
|
Definition
- Simple
- Inherently mathematical
- Doesn't require memory
|
|
|
Term
|
Definition
a tabulation of all the combinations of input values to the corresponding logical output values
|
|
|
Term
|
Definition
uses internal timing devices to determine when to initiate changes in output variables
Examples: Washing machines, dryers, dishwashers
Timers, Drum Timers, and Counters
occur in the same repeated pattern within each regular cycle |
|
|
Term
|
Definition
useful from displaying the relationships between logic elements
- represent combinatorial logic control problems when output variables are based on input values
- sequential control problems
- setting up control programs in PLCs
|
|
|
Term
| U.S. and ISO Symbols for Logical Gates |
|
Definition
|
|
Term
|
Definition
|
|
Term
| Programmable Logic Controllers |
|
Definition
a microcomputer based controller that uses stored instructions in programmable memory to implement
- logic sequencing
- timing
- counting
- arithmetic functions
|
|
|
Term
| Advantages of using a PLC |
|
Definition
- programming is easier than hard wiring the relay control panel
- can be REPROGRAMMED
- take up less floor space than relay control panels
- higher RELIABILITY and easier to MAINTAIN
- can be connected to computer systems easier
- can perform a greater variety of control functions
|
|
|
Term
|
Definition
- Processor (CPU) - executes various logic and sequencing functions
- Memory Unit - store logic
- Power Supply (120 V ac) - converts 120 V ac into dc of 5 V
- I/O module - provides connection to industrial equipment or process to be controlled
- Programming Device - used to program the PLC
|
|
|
Term
| Components of PLC Diagram |
|
Definition
|
|
Term
|
Definition
steps in the control program are executed simutaneously and continuously
Scan consists of 3 Parts:
- Input Scan
- Program Scan
- Output Scan
Scan Time - the time to perform scan
|
|
|
Term
|
Definition
| The inputs to the PLC are read by processor and the status of these inputs are stored in memory |
|
|
Term
|
Definition
| control program is executed and the I/P values stored in memory are used in the calculations to determine outputs |
|
|
Term
|
Definition
| the outputs are updated to agree with the calculated values |
|
|
Term
| Additional Capabilities of a PLC |
|
Definition
- Analog control
- Arithmetic functions
- Matrix functions
- Data processing and reporting
|
|
|
Term
| Standard for PLC Programming |
|
Definition
Graphical Languages
- Ladder Logic Diagram
- Functional Block Diagram
- Sequential Functional Chart
Test Based Languages
- Instructional List
- Structured Text
|
|
|
Term
| Instructional List Programming |
|
Definition
| provides a way of entering the ladder logic diagram into PLC memory |
|
|
Term
|
Definition
high-level computer-type language
the principle advantage is its capability to perform data processing and calculations on values other than binary
|
|
|
