programmable logic controller “ fundamentals of logic…”
TRANSCRIPT
PROGRAMMABLE LOGIC CONTROLLER
“FUNDAMENTALS OF LOGIC…”
THE BINARY CONCEPT…• PLC operates on the binary principle like all digital
equipment.
• Term “binary principle” refer to the idea that many things can be thought of as existing in one of two states.
• states can be defined as “high” or “low”,“on” or “off”, “yes” or “no”, and “1” or “0”.
• This two-state binary concept, applied to gates, can be the basis for making decisions.
THE BINARY CONCEPT…
• Gate device that has one or more inputs with which it will perform a logical decision and produce a result at its one output.
• Logic ability to make decisions when one or more different factors must be taken into account before an action is taken.
“AND” GATE…
ANDLight Switch
High Beam Switch
High Beam Light
The automotive high beam lightcan only be turned on when thelight switch AND high beam switchare on.
FUNCTION OF “AND” GATE…
Binary 1 represents the presence of a signal or the occurrence of some event, while binary 0 representsthe absence of the signal or nonoccurrence of the event.
‘AND’ GATE APPLICATION…EXAMPLE 1
Basic Rules
The device has twoor more inputs andone output
If any input is 0,the output will be 0
If all inputs are 1,the output will be 1
‘AND’ GATE APPLICATION…EXAMPLE 2
The AND gate operates like a series circuit.The light will be “on”only when bothswitch A and switch Bare closed.
“OR” GATE…
Passenger Door Switch
Driver Door Switch
DomeLight
The automotive dome light willbe turned on when the passengerdoor switch OR the driver doorswitch is activated.
FUNCTION OF “OR” GATE…
An OR gate can have any number of inputs but only one output.
The OR gate output is 1 if one or more inputs are 1.
‘OR’ GATE APPLICATION…EXAMPLE 1
If one or more inputs are 1, the output will be 1
Basic Rules
If all inputs are 0,the output will be 0
‘OR’ GATE APPLICATION…Example 2
The OR gate operates like a parallel circuit.The light will be “on”if switch A or switch Bis closed.
FUNCTION OF ‘NOT’ GATE…
The NOT function has only one input and one output.
The NOT output is 1 if the input is 0.The NOT output is 0 if the input is 1.
Since the output is always the reverse of the inputit is called an inverter.
‘NOT’ GATE APPLICATION – Example 1
The light will be “on” if the pushbutton is not pressed.
Acts like a normallyclosed pushbuttonin series with the output.
The light will be “off” if the pushbutton is n pressed.
‘NOT’ GATE APPLICATION – Example 2
If the power is “on” (1) and the pressure switch is not closed (0), the warningindicator will be “on”
Low-pressureindicating circuit
When the pressurerises to close thepressure switch, thewarning indicatorwill be switched "off"
NAND FUNCTION
Functions - like an AND gate with aninverter connected to its output.
The only time the NAND gate output is 0 is when all inputs are binary 1.
NOR FUNCTION
Functions - like an OR gate with aninverter connected to its output.
The only time the NAND gate output is 1 is when all inputs are binary 0.
XOR (EXCLUSIVE-OR) FUNCTION
The output of this gate is HIGH only when one input or the other is HIGH, but not both.
Has two inputs and one output.
Commonly used for comparison of two binary numbers.
GATE BOOLEAN EQUATIONS
AB
YAND Y = A B
Gate Boolean Equation
ORA
BY Y = A + B
NOTA Y Y = A
BOOLEAN EQUATION – Example 1
Each logic function can be expressed in terms of aBoolean expression
BOOLEAN EQUATION – Example 2
Any combination of control can be expressed in terms of a Boolean equation
ABY = AB + C
A + B
Y = (A + B) C
BOOLEAN EQUATION – Example 2
AB
Y = AB + C
A + BY = (A + B) C
Producing A Boolean Expression From A GivenCircuit – Example 1
Producing A Boolean Expression From A GivenCircuit – Example 2
Final equation: Y= AB + AB
Hard Wired versus Programmed Logic
The term hardwired logic refers to logic control functions that are determined by the way devicesare interconnected.
Hardwired logic can beimplemented using relays and relay ladder schematics.
Hardwired logic is fixed:it is changeable only by alteringthe way devices are connected.
Hard Wired versus Programmed LogicExample 4-1
Hard Wired versus Programmed LogicExample 4-2
Hard Wired versus Programmed LogicExample 4-3
Hard Wired versus Programmed LogicExample 4-4
Hard Wired versus Programmed LogicExample 4-5
Hard Wired versus Programmed LogicExample 4-6
Hard Wired versus Programmed LogicExample 4-7
Hard Wired versus Programmed LogicExample 4-8
Hard Wired versus Programmed LogicExample 4-9