One of the features of the BRX Series PLC is the ability to expand its capability to fit your application. This is easily done by “snap-on” modules that will fit on the side of the BRX MPU (Multi Processor Unit). As we have seen before in the BRX PLC System Configuration post we can add additional discrete inputs and outputs. Automation Direct now offers Analog Voltage and Analog Current input and output modules. These modules come as an 8 point channel unit. There is also a 4 point thermocouple input module also available. We will be configuring, scaling and programming the Analog input and output Voltage modules for our BRX PLC. Let’s get started. Continue Reading!
Advanced HMI is a powerful, adaptable HMI/SCADA (Supervisory Control and Data Acquisition) development package that takes advantage of Visual Studio. There is no coding required and you can simply drag and drop items onto the page. The best thing is that the software is free. We will look at using AdvancedHMI with the BRX Series PLC.
Our sample BRX PLC program will display a digital panel meter and a gauge of a value in the PLC. Stop and start momentary pushbuttons on the HMI will allow this number to increase or stop. An indication will turn green when the number is increasing and red when it has stopped. The AdvancedHMI package will communicate Modbus TCP over Ethernet to the BRX PLC. We will be able to monitor our process via the AdvancedHMI window. Lets get started. Watch on YouTube…
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
– 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
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!
The BRX PLC like all of the PLCs in the Do-More Series use strong data typing. This means that there are fixed memory structures to work with in your program. Errors will be displayed if you try to put the wrong type of value in the memory location. The data structures will automatically assist you in your automation system.
Memory can now be as flexible as you want and need. You can define and allocate all the data memory the way you want it up to specific maximums. As a system integrator you determine what best fits your automation framework.
We will be looking at the addressing and numbering systems in the BRX Series PLC. Let’s get started. Continue Reading!
We will now use the Do-More Designer software to establish communication with the BRX PLC. This is the same software that we used in the Learn PLC Programming Fee Video Series. Using the Do-More Designer software, we will communicate via USB, RS485 and Ethernet. These three methods will allow us to communicate to our BRX PLC in order to program or troubleshoot this controller. Once we have established communication we will then look at updating the firmware in our controller. Let’s get started. Continue Reading!
Previously we used VB6 (Visual Basic 6) to implement the Omron Host Link Protocol to communicate to our programmable logic controller. (PLC) In part 2 we used Visual Basic for Applications (VBA) to accomplish our host link serial communication. We will now look at using VB.Net to establish and retrieve information in and out of the PLC using host link. (C mode commands)
Hostlink communication protocol is a method developed by Omron for communication to PLC’s and other equipment. This ASCII based protocol is used over RS232 or RS422/RS485. It is a many to one implementation which means that you can communicate with up to 32 devices back to a master. (1:N) This communication on the industrial floor can control PLC’s, Temperature Controllers, Panel Meters, etc.
The Omron CP1H plc will be used with a CP1W-CIF11 (RS485) communication serial link adapter. We will also use a USB-485M Universal Serial Bus to RS485 adapter from automation direct. The video at the end of this post will demonstrate the communications by reading 10 registers form the DM area of the PLC. Continue Reading!
When I was in school PLC’s were just in their infancy. We were taught that the PLC consisted of the central processing unit (CPU), analog and digital inputs and outputs. Everything was programmed with dedicated handheld devices and/or software devices on specialized hardware. We now have modern PLC systems that are capable of so much more. Let’s look at how we can now break up these modern PLC system into the seven essential components.
Inputs and Outputs (I/O)
Networking Continue Reading…
Understanding how the PLC will scan and update your program is critical in programming and troubleshooting your system. Typically a PLC will solve your logic from left to right, top to bottom. The status of the memory from the previous rung, are available for the next rung to use. We will look at a few examples to determine how the PLC will solve logic to illustrate the above program scanning. Keep on Reading!
We will continue the series by looking at a sequencer controlling seven cylinders that can be taught. The cylinders can be operator programmed from the AdvancedHMI screen. You will be able to select what cylinders to activate at each step and program in 500 steps. Our PLC will be the Do-More from Automation Direct.
Here is a quick review of the programming series so far. If you are new to the site, we recommend reviewing the other parts in the series first.
In part 1 we looked at writing PLC programs to control a traffic light using discrete bits and then using timed sequencing using indirect addressing.
Part 2 used indirect addressing for inputs as well as output to control the sequence of pneumatic (air) cylinders in the program. Part 3 and 4 we returned to the traffic light application and expand our program significantly. We looked at the sequence of operation using Input, output and mask tables.
In part 5 we used the AdvancedHMI software to create the game of Simon. A round in the game consists of the device lighting up one or more buttons in a random order, after which the player must reproduce that order by pressing the buttons. As the game progresses, the number of buttons to be pressed increases.
We will be using AdvancedHMI to communicate Modbus TCP to the Automation Direct Do-More Designer Software Simulator. The following is the sequence of operation:
Watch on YouTube: Running the Cylinder Sequence (PLC / HMI)
Note: All of the programs used are provided free of charge and are an excellent way to learn PLC / HMI programming.
The following table is the Modbus TCP memory map to the Do-More PLC:
|Coil/Register Numbers||Data Addresses||Type||Do-More PLC||Table Name|
|00001-09999||0000 to 270E||Read-Write||MC1 to MC1023||Discrete Output Coils|
|10001-19999||0000 to 270E||Read-Only||MI1 to MI1023||Discrete Input Contacts|
|30001-39999||0000 to 270E||Read-Only||MIR1 to MIR2047||Analog Input Registers|
|40001-49999||0000 to 270E||Read-Write||MHR1 to MHR2047||Analog Output Holding Registers|
|Device||Data Addresses||Type||Do-More PLC||Description|
|Run/ Jog Selector||00008 / 00015||Input/ Output||MC8 / MC15||MC8 is the value and MC15 is the click|
|Light Stack||00010 / 00009 / 00008||Output||MC10 / MC9 / MC8||Red / Green / Amber|
|Jog / Teach Selector||00070||Input||MC70||MC70 on is teach mode|
|Sequence Step (Panel Meter)||40001||Output||MHR1||Current step in the sequence|
|Inputs Actual||40002||Input||MHR2||Show the actual inputs in binary format|
|Output Sequence||40003||Output||MHR3||Show the actual outputs in a binary format|
|Input Sequence||40004||Input||MHR4||Show the input sequence bits in a binary format|
|Cylinder 1 to 7 – value||00001 to 00007||Output||MC1 to MC7||Determine if cylinder is on/off|
|Cylinder 1 to 7 – set (click)||00041 to 00047||Input||MC41 to MC47||Set the cylinder button|
|Cylinder 1 to 7 – retract indicators||00021 to 00027||Input||MC21 to MC27||Indicate cylinder has retracted|
|Cylinder 1 to 7 – extend indicators||00031 to 00037||Input||MC31 to MC37||Indicate cylinder has extended|
|Cylinder 1 to 7 – extend / retract error indicators||00050 to 00063||Output||MC50 to MC63||Indicate cylinder input error when jogging|
The first thing we will do is design the HMI. We have three main areas on the screen. Basic Controls, Cylinder Visualization, and the Sequence Step/Teach area. Please refer to the above reference chart for the inputs and outputs programmed on the screen.
Each cylinder will have indication lights to determine the status of the cylinder. (Extended / Retracted)
The cylinder will also have red indication lights to reflect the differences between the current sequence and the next sequence step. This is visible when we are in jog mode.
When in jog or teach mode the sequence step is visible, which indicates the current step that we are on. The inputs and outputs are displayed as a binary value which represents the actual inputs and outputs. This is valuable when troubleshooting and finding errors in the system. The set button is visible when in teach mode. When pushed the outputs and inputs are set for that step and the sequence will then increment.
The following is the code for each of the words that the DataScribers are reading. This includes the code to change the word into a 16-bit binary value.
Private Sub DataSubscriber1_DataChanged(sender As Object, e As Drivers.Common.PlcComEventArgs) Handles DataSubscriber1.DataChanged 'Label1.Text = Hex(DataSubscriber1.Value)Dim i As Integer = DataSubscriber1.Value Label1.Text = Convert.ToString(i, 2).PadLeft(16, "0") '16 bits End Sub
Private Sub DataSubscriber2_DataChanged(sender As Object, e As Drivers.Common.PlcComEventArgs) Handles DataSubscriber2.DataChanged 'Label2.Text = Hex(DataSubscriber2.Value) Dim i As Integer = DataSubscriber2.Value Label2.Text = Convert.ToString(i, 2).PadLeft(16, "0") '16 bits End Sub
Private Sub DataSubscriber3_DataChanged(sender As Object, e As Drivers.Common.PlcComEventArgs) Handles DataSubscriber3.DataChanged Dim i As Integer = DataSubscriber3.Value Label3.Text = Convert.ToString(i, 2).PadLeft(16, "0") '16 bits End Sub
Private Sub DataSubscriber4_DataChanged(sender As Object, e As Drivers.Common.PlcComEventArgs) Handles DataSubscriber4.DataChanged If DataSubscriber4.Value = True Then Label1.Visible = True Label2.Visible = True Label3.Visible = True Label4.Visible = True Label5.Visible = True Else Label1.Visible = False Label2.Visible = False Label3.Visible = False Label4.Visible = False Label5.Visible = False End If End Sub
We will now look at the PLC ladder program. The program is broken down into several parts as follows:
Indirect Addresses for the Program
V0 – Input pointer – 100 – 499
V1 – Output pointer – 500 – 999
V2 – Input pointer last step in the sequence
V3 – Output pointer last step in the sequence
V10 – Inputs to the sequencer
V20 – Outputs from the sequencer
This section of PLC logic will mimic the inputs from the cylinders.
Cylinder 1 – Retract MC21 (00021) – Extend MC31 (00031)
Cylinder 2 – Retract MC22 (00022) – Extend MC32 (00032)
Cylinder 3 – Retract MC23 (00023) – Extend MC33 (00033)
Cylinder 4 – Retract MC24 (00024) – Extend MC34 (00034)
Cylinder 5 – Retract MC25 (00025) – Extend MC35 (00035)
Cylinder 6 – Retract MC26 (00026) – Extend MC36 (00036)
Cylinder 7 – Retract MC27 (00027) – Extend MC37 (00037)
This is the end of the PLC program. You can see that the program is not very complicated once you break down the individual steps.
Watch on YouTube: Building a PLC Program that You can be Proud Of – Part 6b – Explaining the Program
If you have any questions or need further information please contact me.
If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.
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