Basic OR gate operation explanation using electrical wiring diagram and PLC ladder diagram

Application:-In electrical panel there are two switches given for panel ON lamp. Both the switches are optional, the lamp can be ON either by switch 1 or switch 2.Draw truth table, electrical wiring diagram and write PLC program for this application.

Components:-Programmable logic controller, Electrical panel, wires, 24vDC switches with NO contacts, 24VDC indication lamp, 24 VDC relay.

Diagram:-Electrical wiring diagram and truth table of OR operation

Explanation:-

As per our application, we can use above application for OR gate explanation. In application we are using two switches and one lamp for indication. If switch 1 or switch 2 pressed, indication lamp should be ON. So in above electrical wiring diagram we have used S1 and S2 in parallel connection so electrical supply can flow either from S1 or S2.

In truth table we can easily understand the conditions of OR gate,

As per truth table,

If S1=ON OR S2=ON, then R=1

If S1=ON OR S2=OFF, then R=1

If S1=OFF OR S2=ON, then R=1

If S1=OFF OR S2=OFF, then R=0

So the output will be OFF only in the last condition.

PLC program:-

Write the ladder program for OR gate operation using ladder diagram language. Here for ladder logic we can use any PLC system. For PLC logic we need digital inputs and outputs.

For our application all switches are digital inputs and lamp is digital output. So define digital input address and output address as per below explanation,

Digital inputs:-

S1=I0.0

S2=I0.1

Digital Output:-

Lamp=Q0.0

Memory coil:-

Memory bit-M0.0

PLC program Explanation:-

In network 1 we have considered two digital inputs for two switches S1 and S2. So we have taken NO contact of S1 (I0.0) in parallel with S2 (I0.1) for OR operation. So when S1 or S2 ON, memory bit (M0.0) will be ON.

In network 2 we have taken NO contact of memory bit (M0.0) to operate panel ON lamp (Q0.0).

Basic AND gate operation explanation using electrical wiring diagram and PLC ladder diagram

Application:-Set wiring in the electrical panel so when operator has to operate two switches to operate one lamp. Make electrical control wiring using two switches and one lamp. Also draw truth table for application and write PLC program using ladder diagram language.

Diagram:-Electrical wiring diagram and truth table of AND operation

Explanation:-AND gate operations very important logic in various industrial application. For example purpose we have taken two switches S1 and S2 as shown in above figure. So if operator wants to ON lamp, he has to ON both the switches as per the AND operation. So S1 and S2 must be ON if we want to ON lamp.

In truth table all the conditions has been shown for explanation, it can be easily learned by simple conditional logic,

As per truth table,

If S1=ON AND S2=ON, then R=1

If S1=ON AND S2=OFF, then R=0

If S1=OFF AND S2=ON, then R=0

If S1=OFF AND S2=OFF, then R=0

So output will be ON only in first condition.

PLC program:-Write the ladder program for AND gate operation using ladder diagram language

Here for ladder logic we can use any PLC system. For PLC logic we need digital inputs and outputs.

For our application all switches are digital inputs and lamp is digital output. So define digital input address and output address as per below explanation,

Digital inputs:-

S1=I0.0

S2=I0.1

Digital Output:-

Lamp=Q0.0

Memory coil:-

M=Memory bit

PLC program Explanation:-

In network we have considered two digital inputs for two switches S1 and S2. So we have taken NO contact of S1 (I0.0) in series with S2 (I0.1) for AND operation. So when both are ON, memory bit (M0.0) will be ON.

In network 2 we have taken NO contact of memory bit (M0.0) to operate lamp (Q0.0).

Basic fundamental of NO contact and NC contact

Application:-In electrical panel, operate green lamp with NO contact of relay and operate red lamp with NC contact of relay. Write PLC program using ladder diagram language.

 

Diagram:-Basic operation Machine ON lamp and OFF lamp electrical wiring diagram in the panel.

As shown in figure consider two lamps, red lamp is for machine OFF and green lamp is for machine ON. Once relay will get 24v dc machine ON signal, relay will be ON and green lamp will be ON. We have taken here NO contact for green lamp so supply will pass from C to NO as show in figure and if relay is OFF, supply will pass from C to NC so red lamp will be ON.

Components:-24V dc red lamp, 24V dc green lamp, 24V dc relay, wires, 24V dc source, Programmable Logic Controller

PLC program:-

We can write this logic in PLC also. We can use any PLC for this logic. For logic purpose consider Memory coils and outputs.

M coil:-

M0.0 (NO) =Green lamp ON

M0.0 (NC) =Red lamp ON

Outputs:-

Q0.0=Machine command

Q0.1=Green Lamp

Q0.2=Red lamp

 

PLC program:-

We can write this logic in PLC also. We can use any PLC for this logic. For logic purpose consider Memory coils and outputs.

PLC program explanation:-

In network 1 we have taken NO contact of machine command (Q0.0) so when machine command is ON, green lamp (Q0.1) will be ON.

In network 2 we have taken NC contact of machine command (Q0.0) so when machine is off, red lamp (Q0.2) will be ON.