To day we study how to program in Siemens PLC. We are going to start with basics. There are many types of language for programming but the most popular and easy language is Ladder language.
I illustrate all examples by ladder programming language.
NO is a switch which is Off (0) all the time and when it is pressed it turns On (1). NO means normally open.
NC is a switch which is On (1) all the time and when it is pressed it turns Off (0). NC means normally closed.
Output or coil is on when circuits complete or it is off.
NO and Coil
As shown in above figure we take one No switch connected with coil in ladder language in Siemens. Double click on NO and give address of it ( i0.0). Double click on coil and address it (Q0.0).
Now run your program. When you press NO coil on and again press NO and coil off.
There is chart in Siemens plc blog where you can find address for inputs, outputs, counter, timer etc for Siemens plc.
NC and Coil
As shown in above figure we take one NC switch connected with coil in ladder language in Siemens. Double click on NC and give address of it ( i0.0). Double click on coil and address it (Q0.0).
Now run your program. Coil is on at starting. When you press NC coil off and again press NC and coil on.
There is chart in Siemens plc blog where you can find address for inputs, outputs, counter, timer etc for Siemens plc.
NO, NC and Coil
As shown in above figure we take one NC and one NO switch connected with coil in series in ladder language in Siemens. Double click on NC and give address of it ( i0.0).Double click on NO and give address of it (i0.1). Double click on coil and address it (Q0.0).
Now run your program. Coil is off at starting. When you press NC, coil is off. When you press NO coil turns on. When you press both switch at time then coil is off.
There is chart in Siemens plc blog where you can find address for inputs, outputs, counter, timer etc for Siemens plc.
Holding Circuit
It is NO holding circuit. Holding circuit is used to hold output result. Let us suppose we press a NO switch and coil turns on but after releasing switch coil turns off but If you want to turn light on after releasing switch then use holding circuit as shown above.
As shown in above figure we take one NO (1) switch connected with coil and a feedback NO switch for first NO (2) switch in ladder language in Siemens. Double click on NO (1) and address it (i0.1). Double click on feedback NO (2) and give address of it ( Q0.0). Double click on coil and address it (Q0.0).
Now run your program. Coil is off at starting. When you press NO coil off and release switch and you can see still coil is on. To turn off you can force off feedback NO or stop and run program.
Similar for NC.
There is chart in Siemens plc blog where you can find address for inputs, outputs, counter, timer etc for Siemens plc.
Toggle switch
There are two types of toggle switch as shown below….
Toggle by memory
Make a circuit in plc ladder program as shown above and address it.
The above picture shows how to make toggle switch by memory and switches. Memory is a kind of register where data is stored temporarily.
In toggle switch when you press X0 (i0.0), Y0 (Q0.0) turns on. And when you again press X(0), Y(0) turns off. Turning light on and off by single switch is a purpose to make toggle switch. It turns on or off till switch pressed again.
Toggle by counter
Make a circuit as shown above in your ladder program.
This is toggling of switch by counter. Counter is a function of PLC which counts the number like counting of pressing switch. This is up counter which counts upwards.
Address NO X0 (i0.0) and coil Y0 (Q0.0). Next NO switch addressed as C0=1. When you press X0 once, Y0 turns on. Again press X0 and counter is reset means counter value turns zero. As we give command (C0=2) at reset of counter shown in figure.
This is it guys for basic programming in Siemens PLC. We will discuss more and some industrial program tomorrow.
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