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Hello everyone, welcome to automation
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community. Today in this video we are
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going to discuss an example
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in which we will be drawing ladder
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diagram for boolean expressions. So
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Example 14. Y1 is equal to a1 + b1 dot
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c1 + d1. Then we have y2 is equal to a2
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+ b2 dot c2. So for the first boolean
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expression we have four inputs a1 b1 c1
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there is an or logic gate between a1 and
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b1. That means we need to connect a1 and
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b1 in parallel to each other. And then
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we need to connect C1 and D1 in parallel
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with each other but in series with A1 +
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Similarly, we need to connect A2 and B2
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in parallel and then C2 in series. So
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for all these inputs, we will be using
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normally open contacts. So let's move to
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codices where we will draw a ladder
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diagram for both the boolean expressions
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one by one. So I will open codices.
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So firstly we need to create a new
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project. Click on new project
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and then we need to uh give name to this
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project. Let's say example
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14. And then we can uh select the
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template as standard project and click
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on okay. So the new project is being
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and then we will uh select the device
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from the this drop-down list and then we
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will select PLC programming as ladder
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logic diagram and click on okay
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and then we will double click here PLC
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programming and here we will draw the
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ladder diagram. So firstly we have a +
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b. So we will insert a normally open
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a1 and then we have then plus b1. So
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plus means we need to connect one more
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normally open contact in parallel to
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this a1. So I will insert a normally
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open contact in parallel with this and
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And then we have dot. dot means whatever
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we have to use we will add those
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contacts in series with this A1 plus B1.
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So we will insert contacts here. So here
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I will insert a normally open contact
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here. So let me show you once again.
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First click here and then add a normally
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open contact. Okay. So if we click here
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and then then add a normally open
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contact. So it will be in parall to P1.
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So we don't need to do this. So let's
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click here and then add a normally open
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contact. And this will be C1.
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Okay. And then we will insert a normally
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open contact with parallel to C1 like
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Okay. and this will be
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Okay. And then we will insert a coil for
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So this output Y1 will be on when
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either A1 and C1 should be on or A1 or
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and D1 should be on or B1 and C1 should
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be on or B1 and D1 should be on. So any
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one of these two inputs should be on and
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any one of these two should be on either
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A1 or C1 should be on or B1 or D1 should
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So if C1 and D1 is on then output Y1
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will not be on. So either A1 or B1
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should be on and C1 or D1 should be on.
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And then we have one more boolean
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expression that is a + b dot c. So a + b
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means we need to connect a and b in
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parallel to each other. So we will uh
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insert network below this and we will
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insert a normally open contact for a2
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and then we have plus b2 plus b2 means
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we need to connect a contact
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paddle. So this will be P2 and then we
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have dot C2. So for that we will click
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here and add an orally open contact
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and this normally open contact will be
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and then we will insert a coil and this
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coil will be Y2. So for Y2 to be on
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either of the two inputs should be on
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and C2 should be on. Either A2 and C2
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should be on or B2 and C2 should be on.
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Let's generate code here.
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Go to online and start simulation.
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So firstly I will make A1 true. Let's
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debug it and write values. So, Y1 is
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still off. So, A1 is on and we need to
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turn on either of these two inputs.
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Either C1, we will turn on C1 or we will
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turn on D1. So, when I when I turn on
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C1, go to debug and write values. You
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can see here Y1 will turn on. So the
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signal is passing through A1 and C1
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because both of these contacts are true.
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And then instead of C1 when I will turn
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on D1, let's debug it.
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And you can see here Y1 is still true
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because the signal passes through this
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A1 and then goes like this and then
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passes through D1 because D1 is true, A1
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is true. So the signal will pass through
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this. As a result, this Y1 will turn on.
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And then instead of A1, if I turn on B1
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B1 and D1, let's debug it. And you can
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see here Y1 is on because the current
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the signal will pass through this. As a
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result, Y1 will be on. And then instead
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of D1, I will turn on C1. And let's see
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what happens. Let's debug it. and write
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values. You can see here the signal is
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passing like this. Then passes through
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C1 and Y1 will turn on and then instead
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of C1 I will turn on A1 and B1. Let's
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see what happens. A1 and B1 is true.
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Then what will happen? The output Y1
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will not be true because the signal
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passes through this. The signal passes
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through this but does not pass through
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this. As a result, this Y1 will turn
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off. So then after that I will turn on
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C1 and D1. Let's debug it. Write values.
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So the output Y1 will not turn on
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because the signal is not passing
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through A1. The signal is not passing
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through B1. As a result, this Y1 will
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And then we have one more boolean
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expression here that is Y2 is equal to
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A2 + B2 C2. So A2 and C2 should be on or
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B2 and C2 should be on. Okay. So I will
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turn on A2. Okay. Let's debug it. See
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right values. So this output Y2 will not
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turn on because the signal is passing
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through A2. But C2 is false. It will not
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allow signal to pass through this. As a
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result, Y2 will remain off. And then I
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will turn on C2. I will turn on C2.
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right values. And you can see here Y2
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And then instead of A2, I will turn off
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Let's see. And you can see here the
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signal will pass through B2 because it's
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true. And also passes through this C2
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because it's true. As a result, this Y2
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will turn on. And when I turn on A2 and
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B2 and turn off C2, let's debug it and
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write values. You can see here Y2 is
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false because A2 passes the signal. B2
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passes the signal but C2 does not pass
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the signal. As a result, this Y2 will
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not turn on. It was all about this
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example. Thank you for watching.
