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PLC Hardware Components - Coggle Diagram
PLC Hardware Components
I/O Section
Input
Accepts signals from the machine or process device
Converts signals to be used by the controller
Output
converts controller signals into external signals
Provides Interface
connects hard-wired components and the CPU
input provides interface for status information
Slot
Physical location of I/O module
Word and Bit
identifies actual terminal connection
Discrete I/O Modules
Most Common I/O type
connects On/Off type devices
Switches, push buttons etc...
output is limited
Things such as lights, relays, etc...
performs 4 tasks
Sense signals received
inputs
Converts Signals
corrects voltage levels
Isolates PLC
Prevents fluctuations in input signals
Sends signals
sends to processor indicating which sensor the signal came from
Analog I/O modules
can have an infinite amount of input values
vary in amperage and voltage
0-20mA and 4-20mA
0-10 volts
uses
tank level indicators
temperature
speed control
I/O Specifications
Nominal Input Voltage
Designed voltage module can accept
Input Threshold Voltages
minimum ON-state
Maximum OFF-state
Nominal Current Per Input
minimum input current capable of driving the operation of the circuit
CPU
Brains of PLC
utilizes ladder logic for programming
And, Or, Nor, Not, etc...
Can be used for SCADA
Supervisory Control and Data Acquisition
Memory Design
Element that stores information
Stored as 1's and 0's
Determined by complexity of program
how many bits
Memory Types
EPROM
Erasable Programmable Read Only Memory
Provides security
EEPROM
Electrically Erasable Programmable Read Only Memory
ROM
Read Only Memory
Can only be read
RAM
Random Access Memory
Can be written and read