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hello everyone myself
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badas in this video I will discuss about
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interlock and a simple example
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interlock see interlock is a safety or
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mechanism that pre vents certain actions
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unless specific conditions are met see
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this is a basic definition of an
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interlock interlocks are very important
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in Industries generally we will use
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these interlogs such that we can prevent
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some safety related accidents see these
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the first one is machine guard a machine
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won't run if its safety door is open for
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machine and the operator given the start
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command for the machine but its safety
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door is in open condition instead of
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close when there is an interlock for
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this safety door is there
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then even though the operator given the
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start command but the mission will not
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start because the door sensor interlock
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motor okay the program will not be
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active or will not activate the output
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command even though the operator given
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the start command because of the safety
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another example is conveyor
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belt a conveyor belt won't start unless
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all emergency stop buttons are
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released for every machine motor pump
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Etc all the machines in
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Industries will have the emergency stop
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buttons the default state of the stop
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buttons must be in release State
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okay then only the machine will
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start this is also one of the basic
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interlock example okay now we will
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discuss one example we'll go to the
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example the example is interlock for two
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outputs develop a PLC program to control
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a motor forward and reverse
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rotation using two switches s W1 and S
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W2 there is a motor the motor
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output either it can rotate in forward
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Direction when the output q1 is in on
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or it can rotate in Reverse Direction
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when the output Q2 is in on state these
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two outputs are directly controlled
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using two switches if switch one is on
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then the motor rotates in forward
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direction that means q1 will be on if
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switch 2 is in on state then the motor
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rotates in Reverse direction that means
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that only one output is active at a time
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okay the motor can rotate either in
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forward direction or in Reverse
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Direction definitely it will not rotate
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in both directions at a time if you give
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such type of command then the motor will
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be damaged so we have to prevent these
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type of Damages using
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interlocks okay if both switches are on
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at a time then all outputs is in off
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when switch one is on q1 will be on when
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switch two is on Q2 will be on if In
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Case by mistake operator presses both
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switches at a time then all outputs
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should be in off State so this is a
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basic interlock for two
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outputs now open your
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software now take two
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inputs and I will take I3 and I4 you can
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input add the comment also I3 is my
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one and I4 is my switch to
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now for interlock purpose I will
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use basic functions end gate
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okay take two end blocks and give the
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command the top one is my
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and second one is my end
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two now connect first end gate output
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with q1 and second end gate output with
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Q2 now connect switch one input
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3 to the first first input of
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endgate similarly connect switch to with
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first input of second end
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gate now connect switch one with the
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last input of second end
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gate similarly connect switch to with
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the last input of first end
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overlapping so that we will have better
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Clarity okay now what I will do I want
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to add one not gate to the second input
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of both the end Gates either you can use
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the not block from the basic functions
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or what I will do I will just do this
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simple double click of the second
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input then one bubble will appear
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this means the input is inverted the
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knot is added similarly I will press two
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times in the second handgate
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also not get is added this is the
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hardware and download the
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program if you don't have the PLC
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Hardware with you just do the simulation
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logic I suggest you to open your PLC
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software and practice the program
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instead of Simply watching the videos
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you will not remember after some time if
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you only watch the videos you must
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practice the lesson or examples or
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assignments or tasks you must perform
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hands and now I go to the online
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mode select the IP and click
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now when I press the switch one when I
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turn on the switch one M forward will be
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active that means q1 will be on see
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switch one is on the first endgate two
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inputs are on on state the first input
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is switch one it is in on State and the
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second input is switch
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two but the not is added that is why
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switch to is in off State and with
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because of not it is in on and endgate
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both inputs are in on state the output
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on now what I will do I will turn off
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one and turn on switch
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happens the second end gate output is on
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that is why output Q2 is on that means
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motar is rotating in Reverse Direction
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you can see the second and gate inputs
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are in on state that is why output is in
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on state let's suppose in this case I
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will turn on the switch one that means
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both switches are on at a
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time in this case the outputs are in off
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State both are in off Swit
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State the not BL gate are not input of
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making the outputs in off State
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simple this is very simple
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logic using and and not blocks okay
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practice this logic and one more simple
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task for you is this is a interlock of
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two outputs now consider interlock of
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three outputs you have three inputs
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switch one switch two switch three and
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you have three outputs q1 Q2
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Q3 switch one is when switch one is in
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on state q1 will be on when switch two
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will be in on state Q2 will be on when
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switch three is in on state Q3 will be
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okay if two switches or three switches
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are on at a time then all outputs must
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okay now now try to solve this logic and
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us how you implemented this logic
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remember this second task is similar to
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the same program which is we discussed
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here I just added one more input and one
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more output okay thank you I will meet
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you in the next video
