Basic NAND gate operation explanation using the electrical wiring diagram and PLC ladder diagram

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

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

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

In the truth table, all the conditions have 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=0

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

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

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

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

PLC program:-Write the ladder program for NAND 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 the lamp is a digital output. To 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 1 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 NAND operation. So when both are OFF, memory bit (M0.0) will be OFF.

In-network 2 we have taken NC contact of memory bit (M0.0) to operate lamp (Q0.0).