PLC Flashcards
PLC
Programmable logic controller
PAC
Programmable Automated controller
Analog
Range, Constantly On
Discrete
2 states, true/false , 1 / 0 , on or off
Which device is not an input device
- push button
- limit switch
-pilot light - proximity sensor
Pilot light
PLC Characteristics
-operated by plant engineers / maintenance personnel
-operated in industrial environments
- varies in temp. Vibration. Humidity.
- not affected by electrical noise
- no moving parts
PLC COMPONENTS
- processor unit
- microprocessor “brain”
- power supply
- converts 120-240 v ac to LV dc
- separate unit
- inputs /outputs
- inputs
- buttons , switches , sensors
- outputs
- motor starter coils , solenoid valve , light
- inputs
- programming device
- used to enter program into memory
- computer most common device
Types of I/O Devices
Discrete
- either on / off , open / close
- ex. limit switches , push buttons
Analog
- range of possible values
- ex. temperature , pressure sensors
PLCS ARE USED TO CONTROL
Process machinery
PLCS ARE USED TO CONTROL
Process machinery
PLCs are programmable for fast and easy changes in
Relay ladder logic
PLCs are designed to be used by
Electricians / technicians
- easy to program
I / O SECTION - CHANGES WHAT INTO WHAT
Changes voltage/current signal into logic level signal
- compatible w/ processor
- common v - 24VDC , 5VDC (TTL) , 120 VAC
I / O SECTION - DISCRETE INPUT MODULES PROVIDE
ON / OFF - buttons / switches to processor
- signal sent to output device based on program logic
WHAT IS A PROCESSOR
PLC
INPUT / OUTPUT DEVICES ARE ELECTRICALLY CONNECTED TO THE PROCESSOR
TRUE / FALSE
FALSE
I / O SECTION - LADDER LOGIC
- Discrete input signals modules provide ON / OFF signal to processor
- From the processor it sends a signal to output device based on program logic
- Discrete output modules receive output status from processor and turns on/off output devices such as motor starter coils, pilot lights
FIXED I/O
Complete unit containing processor , I/O section and power supply
Add expansion units with various I/O configurations
- provide more capability
Modular I/O
- More flexible than fixed I/O
- various types of input/output modules
- housed in rack or chassis - local I/O
- mounted w/ processor - remote I/O
- processor is mounted remotely from I/O
LOCAL I/O
I/O modules are mounted with the processor
Remote I/O
Processors mounted remotely from I/O
