Always ON and OFF Bit using Ladder Logic and Statement List

In this article, I will discuss how to create always ON and OFF bit in PLC programming using ladder logic and statement list in Siemens Simatic Manager.

Say in the plant when the machine lost its power and comes back after some time, then we need some functions to perform automatically when starting the machine.

For examples like a cold start or hot start, you want some facility to remain ON and some to remain OFF. The below discussed small two lines of code are used there.

There are many instances in the industry where we require to make some blocks always ON or OFF as per our applications.

In siemens PLC, you can use DB address or bit memory address to create always ON and OFF bit.

To create always ON and OFF bit, we simply have to write code OB and use that memory address anywhere in the program.

To create a bit, first, open Simatic Manager. Create a new project. Now I am going to write code in ladder logic and in statement list too.

You can write code in Function and then you can call it from OB or you can write in OB and you can use its address in the programming.

Always ON and Always OFF bit using STL

The below is the programming window of statement list (STL) where I have written the code of Always ON and OFF bit.

Network 1:

I simply have used memory bit with AND NOT (AN) means NC contact in ladder logic.

In the second line of code, I have used “s” to set the same bit which I have used as input which allows this bit to remain always ON.

Network 2:

In this network, everything is the same except I want a bit to stay always OFF, I have used “R” means reset as an output coil.

Always ON and Always OFF bit using Ladder Logic

This is the window of ladder logic programming.

Network 1:

Here, in Network 1, I have used NC contact which always passes a signal, at output side set coil is used the same as input which makes it always true.

Network 2:

In network 2, I have used the Reset coil at the output side to make the bit always false.

Author: Suhel Patel

If you liked this article, then please subscribe to our YouTube Channel for PLC and SCADA video tutorials.

You can also follow us on Facebook and Twitter to receive daily updates.

Comments

What is a Torbar? – Averaging Pitot Tubes

The Torbar is employed for flow measurement of liquids, gases, or steam in circular, square, or rectangular section ducts for large flow rates. The Torbar is an insertion type multi-port self-averaging primary sensor for flow measurement. Torbar TORBAR is a set of Pitot tubes mounted on a bar across the pipeline with no moving parts. An averaging Pitot tube is a technology, while TORBAR is a manufacturing brand name. There are several brands available in the market with VERABAR, ANNUBAR, etc. Averaging Pitot Tube Principle Purpose Averaging Pitot tube can be employed when the average velocity of the flow profile, rather than the velocity in a specific point in the cross-section is desired. Averaging Pitot Tubes Principle It measures the differential pressure between the static pressure tap and the tap of full pressure of a stream. Thus such magnitude of differential pressure is directly proportional to the square of the flow rate. Working The TORBAR is designed in such a way that ...

Ferrules and Cross Ferruling

Ferrules are identification labels provided for every wire terminations in an instrument, equipment, or electrical/instrumentation control panels. These tube-shaped sleeves can be inserted easily on each individual wire in a multi-core cable. In earlier days fixed digits/letters are used as ferrules, but now Instrumentation engineers/technicians prints out desired ferrules by using a ferrule printing machine. Typical Ferrule The numbers/ letters on the ferrules will be given as per the approved electrical hook up or loop diagrams. This helps technicians to easily identify a particular loop/wiring from a series of terminal blocks and to troubleshoot the desired terminal connection. Separate numbers on the ferrules distinguish the positive and negative polarities of wires, thus ensure the polarity protection of the instrument. Cross Ferruling As a wire is connected on its both ends, it is quite useful to use a cross reference method for wire identification. Unlike normal ferru...

The Method and Process of Siemens PLC Hardware Configuration

The hardware configuration of Siemens PLC can usually adopt the following methods and processes: Determine control tasks and system requirements: Before hardware configuration, it is necessary to clarify the tasks and requirements of the control system, including the requirements for input and output points, control accuracy, speed, and safety. Select the PLC model and module: According to the control task and requirements, select the appropriate PLC model and module, including CPU, I/O module, communication module, power supply module, etc. Assemble the cabinet and install the modules: According to the selected PLC model and module, assemble the cabinet and install the modules, pay attention to the installation sequence, cable wiring, wiring method, etc. Connect the input and output devices: connect the input and output devices with the input and output modules of the PLC, you need to pay attention to the correctness, stability and safety of the wiring. Perform software configura...

TILI Automation

Search This Blog