All posts by garrys

BRX PLC Drum Instruction

Drum instructions are great tools when you have a simple sequence of events that need to occur at a set time interval or as a result of an event. They mimic an electromagnetically drum sequencer. The BRX Series PLC has a drum in the instruction set.
Have you ever seen the mechanisms of a music box? Ok so it’s a little drum with pegs that catch and flick the chimes in a particular sequence to play whatever tune is on the drum. So in the PLC you can have a drum driven by an event, (input from a limit switch or button), or by time.
We will discuss the drum instruction and look at an example of controlling traffic lights with a cross walk signal. Continue Reading!

PLC Programming Example – Palletizer Drum Instructions

How many ways can you program the PLC for the same function? The answer is allot of different ways. You can have ten different programmers working on the same program and get ten different automatic control PLC programs. Sure they may have similarities but, they are all unique in their code within the PLC. As a system integrator you will see many different ways of programming the PLC. We will now look at reprogramming our palletizer example using drum instructions. (Sequencer)
Last time we applied the five steps to PLC program development to a palletizer example. We will review our steps and then change our programming code to incorporate the drum instructions. Like our original example we will allow the operator to change the layers of boxes you want on each skid. We will also add in this example a manual operation sequence to cycle thought each of the steps for troubleshooting the program.

Developing the PLC program is a process that can be clearly defined. In our series on the five steps to PLC program development we have done some similar practical examples.
PLC Programming Examples – Five Steps to PLC Program Development
– Press
Process Mixer
Shift Register (Conveyor Reject)
Paint Spraying
Delay Starting of 7 Motors
– Pick and Place
– Sorting Station (Shift Register)
Palletizer

Define the task: (1)
Watch the sequence of operation video below. This will demonstrate the pallet layer selection, running and resetting of the machine.
Watch on YouTube : PLC Programming Example – Palletizer Testing
Continue Reading!

PLC Fiddle – Online Editor and Simulator in your Browser

I have recently come across a free virtual plc simulator called PLC Fiddle. It will enable you to create simple PLC ladder logic code within your browser. This is an ideal way in understanding PLC concepts for industrial automation. All of the basic PLC instructions that come with most plc units have been incorporated in this virtual PLC software.
PLC Fiddle is currently in an early stage of development but is functional enough to be helpful to you in learning and understanding PLC concepts. We will be reviewing this software and creating a few common basic circuits. Using the simulator we will test our circuits and monitor our PLC programs (circuits). Let’s get started. Continue Reading!

BRX PLC Shifting Instructions

PLC shifting instructions will move bits in memory areas a fixed amount when instructed. Bits are on/off, 1 or 0 and are usually associated together to form a memory location. The memory location can be used for numbers or positions.
PLC BITS NUMBERS AND POSITION is a post that will review the different methods that the PLC will interpret the information in memory
We will be looking at the shifting (moving) of the bits within the memory location in several different ways. ROTL rotate left, ROTR rotate right, Math shift left operator, Math shift right operator, Math unsigned shift right operator and SR shift register are some of the instructions in our BRX PLC that will shift bits.
Let’s look at some samples of each of the above mentioned instructions. Continue Reading!

BRX PLC Program Control

The program control instructions will allow us to specify what parts of the logic get solved and when this happens. This will control how the PLC will scan and solve your logic in your program using a synchronous PLC Scan. Understanding the PLC program scan will explain the synchronous and asynchronous program scanning. Ladder logic programs get solved left to right, top to bottom. The result of the rung before is available for the next rung.
Using programs, tasks and subroutines in our BRX Series PLC we can divide up our program into smaller segments. This will help when we troubleshoot the system in the field as the system integrator. Let’s look at some samples of each of the above mentioned methods. Continue Reading!

PLC Programming Example – Palletizer

We will apply the five steps to PLC program development to a palletizer example. Our example will allow you to determine how many layers of boxes you want on each skid.

Developing the PLC program is a process that can be clearly defined. In our series on the five steps to PLC program development we have done some similar practical examples.
PLC Programming Examples – Five Steps to PLC Program Development
– Press
Process Mixer
Shift Register (Conveyor Reject)
Paint Spraying
Delay Starting of 7 Motors
– Pick and Place
– Sorting Station (Shift Register)

Define the task: (1)
Watch the sequence of operation video below. This will demonstrate the pallet layer selection, running and resetting of the machine.
Watch on YouTube : PLC Programming Example – Palletizer Testing
Continue Reading!

BRX PLC Math Instructions

Math instructions are used to perform mathematical calculations. The BRX PLC has math instructions that can be used in a wide variety of applications. We will be looking at the INC increment, DEC decrement, LERP linear Interpolation, RANDSEED Random Number Seed and the MATH Calculated Expression instructions. Your automation system that you implement may involve some or all of these instructions. As a system integrator you will require the use of these instructions in your commissioned programs.
Let’s get started with the BRX PLC Math Instructions. Continue Reading!

BRX PLC Compare Instructions

Compare instruction are often used in PLC programs to test pairs of values. The output of this comparison conditions the logical continuity of a rung. The BRX series of programmable logic controllers has the following compare contact instructions.
= (if Equal contact)
<> (if Not Equal contact)
> (if Greater Than contact)
>= (if Greater Than or Equal contact)
< (if Less Than contact)
<= (if Less Than or Equal contact)
Besides these instruction the BRX PLC will also have compare instructions for the built in real time clock of the system. We will be looking at these instructions along with some programming examples. As a system integrator, this ability can prove very useful to you in the field when commissioning your automation system.
Lets get started with the BRX PLC Compare Instructions. Continue Reading!

PLC Programming Example – Sorting Station (Shift Register)

We will apply the five steps to PLC program development to a sorting station example. The program will use shift registers to track coloured parts down a conveyor and sort depending on colour into one of three locations.

Developing the PLC program is a process that can be clearly defined. In our series on the five steps to PLC program development we have done some similar practical examples.
Five Steps to PLC Program Development
– Press
Process Mixer
Shift Register (Conveyor Reject)
Paint Spraying
Delay Starting of 7 Motors
– Pick and Place

Define the task: (1)
Watch the sequence of operation video below.
Watch on YouTube : PLC Programming Example – Sorting Station Testing
Continue Reading!

Modbus RTU BRX PLC Master to Click PLC Slave Communication

Recently I was asked to demonstrate communication between a BRX PLC and Click PLC using Modbus RTU. Both PLCs are available from automation direct com. Modbus serial communication (Modbus RTU) is a standard protocol used in many automation devices. It works on a Master / Slave configuration. You can have only one master per network on Modbus RTU (Remote Terminal Unit). A maximum of 32 devices (Nodes) on the network can communicate to the master. A review of the Modbus RTU protocol (RTU frames) can be seen at the following URL.
http://www.rtaautomation.com/technologies/modbus-rtu/
Using the BRX PLC as a Master, we will be communicating to the Click PLC (Slave). Our example will read 10 registers from the Click PLC and write 10 registers from the BRX PLC. Let’s get started! Continue Reading!