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.

Motor Start/Stop operation with trip indication lamp

Application:-There is one machine in the factory, we want to start/stop motor using push button g from the panel. Give motor ON lamp and motor trip lamp on the panel. When motor is running ON lamp should be ON and if motor trip due to some problem, trip lamp should be ON. Write the PLC program in LAD and FBD language.

Solution:-Here we will make PLC program in the PLC so operator can operate motor from the panel and get indication on the panel. And also we will take inputs signal and outputs for our application

Diagram:-

 

PLC Program:-Write the PLC program from above application using LAD diagram language.

PLC program explanation:-

As per our application we wrote PLC program. In this program we have considered following inputs and outputs for our application. We can use any make PLC for our application.

Inputs:-

Start Button:-I0.0

Stop Button:-I0.1

Trip Input:-I0.2

Outputs:-

Motor:-Q0.0

Motor On Lamp: Q0.1

Trip Lamp:-Q0.2

Network 1:-In this network we are starting and stopping motor by push button. By pressing Start (I0.0) motor can be started and by pressing stop PB (I0.1), motor (Q0.0) can be stopped.

Network 2:-In this network we wrote the logic for motor ON lamp or indication (Q0.1). SO when motor is running, Motor ON lamp is also ON.

Network 3:-For safety purpose we have considered here trip lamp (Q0.2). So when trip signal (I0.2) is ON, trip lamp is also ON.

Analog signal concept

Selecting sensors 0-10 VDC, 4-20mA and 0-20mA

What we will Learn……..

-Understand the concept of voltage and current sensor feedback

-Difference between voltage input signal and current input signal

-Why do we use 4-20mA signal instead of 0-20mA signal?

-Why do we use current signal instead of voltage signal?

-In the domain of straight position sensors, straightforward guidelines. Sure there are a wide scope of other sensor interface types available; propelled starting/stop, synchronous consecutive interface, various types of fieldbus, and so forth.

-In any case, direct position sensors with basic yields in spite of everything speak to probably 66% of all straight position sensors sold.

-While picking a basic yield position sensor, your choice all things considered comes down to straightforward voltage (e.g., 0 to 10 V), or basic current (e.g., 4 to 20 mA). So which would it be prudent for you to pick?

Difference between 0-10 V DC sensor and 4-20mA sensor

Selection of 0-10 VDC sensor in PLC system

-With respect to sensor interface signals, 0-10V takes after vanilla solidified yogurt or, in case you like, a Chevy Cavalier. It's very little, anyway it do what needs to be done'.

- It's typical, it's unmistakable, it's definitely not hard to research, and pretty much every cutting edge controller on the planet will recognize a 0-10V sensor signal. Nevertheless, there are a couple of downsides.

- Each and every basic sign are unprotected to electrical impedance, and a 0-10V sign is emphatically no exclusion. Devices, for instance, motors, moves, and "noisy" power supplies can start voltages onto signal lines that can degenerate the 0-10V sensor signal.

-Also, a 0-10V sign is powerless against voltage drops achieved by wire restriction, especially over long connection runs.

Selection of 4-20mA 0r 0-20mA sensor in PLC system

-A 4-20 mA or 0-20 mA signal, on the other hand, offers extended invulnerability to both electrical impediment and give mishap up long connection runs.

-Also, generally more cutting-edge present day controllers will recognize current signs.

-In the event that that wasn't at that point enough, a 4-20 mA signal gives trademark bumble condition area since the sign, even at any rate worth, is up 'til now powerful. Without a doubt, even at the over the top low end, or "zero" position, the sensor is so far giving a 4 mA signal. In case the value ever goes to 0 mA, something isn't right.

-The comparable cannot be said for a 0-10V sensor. Zero volts could mean zero position, or it could suggest that your sensor has halted to work.

-From time to time, 4-20 mA sensors can be insignificantly continuously costly appeared differently in relation to 0-10V sensors. However, the cost differentiation is getting dynamically smaller as more sensor types join current-yield capacity.