A dusk to dawn sensor usually is discrete on/off of the lighting control. If we want to vary the lights to mimic more of the sunset and rise, we would use an analog output to control the lights. I was recently asked about such a program. Every day they wanted the lights to go off at 10 pm and come back on at 6 am. At 9:30 pm the lights would be on at 70% or 7volts of a 0-10V signal. In the next half hour, the program will bring the lights from 70% down to 0%. In the morning the lights will come back on within the half-hour from 0% to 70%. Poultry Farms are one place that would utilize this program.
We will be developing a program that will do this with our BRX PLC (Do-More). Let’s get started! Continue Reading!
One of the features of the BRX Series PLC is the ability to expand its capability to fit your application. Software and hardware changes are ongoing so the PLC can grow with your needs. Communication is something that the BRX PLC can do very well. As part of the internet of things (IoT), the BRX will share and exchange data. You can also refer to this as the industrial internet of things. This will suit several industrial applications.
The Do-more Updates Release 2.5.2 on April 22, 2019, has introduced new instructions. Here are the instructions that we will be using:
HTTPCMD – HTTP Request / Response with Server (BRX only)
JSONPARSE – Parse JSON Text (BRX only)
We will be using these instructions to read the weather conditions from a website. Let’s get started. Continue Reading!
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Sending email messages from the PLC sounds like an easy task. However, very few applications do this on the production floor. This is probably due to the networks involved and user authentication can be complicated. In our example, we will use a restricted Gmail SMTP server so no authentication will be required. We will walk through sending email and text messages from the PLC to Google Gmail. Once in your Gmail account, the message can be automatically forwarded to another verified email or SMS text message address.
The BRX Series PLC also has this Email capability along with attaching files. We will also be looking at secure email services with the BRX Series PLC. Let’s get started. Continue Reading!
Data logging does not have to be complicated anymore. The BRX Series PLC can log your specific data up to 32 Gigabits on a Micro SD Card. It will store your data for future data analysis in a CSV (Comma Separated Value) Txt file based on time and/or event.
This is all accomplished with just one instruction in the BRX PLC. Excel is just one program that you can import and analysis this CSV Text file.
Do-More Designer has a Browse PLC File Systems window that will allow you to copy, create and delete the files from the connected computer. This will save you from going to each controller, removing and copying the files on the Micro SD Card.
We will be looking at the data logging instruction in the BRX Series PLC and how to retrieve and view this information. Let’s get started. Continue Reading!
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!
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!
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!
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.
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!
The BRX series of programmable logic controllers has built in high speed inputs and outputs. Every CPU will have either 6 or 10 high speed inputs (HSI) available depending on the model. These inputs can be used for input frequencies from 0 to 250Khz. 250Khz represents 250000 input counts per second that can be coming from devices connected to your PLC like an encoder. Every BRX CPU unit also has 2, 4 or 8 high speed outputs (HSO) available depending on the model. The outputs can send a frequency of pulses out up to 250Khz. Due to the speed of the IO, these functions available on the BRX PLC will operate asynchronous with the PLC scan time.
We will be looking at sending an output of pulses at different frequencies from our BRX PLC and inputting these back into the high speed inputs of the PLC. So our output will be wired back into our input. We will then display the frequency of the input pulses and the count. As a system integrator, this ability to send and receive high speed inputs and outputs can prove very useful to you in the field when commissioning your automation system.
Let’s get started with the BRX PLC High Speed IO. Continue Reading!