We will look at the BRX Do-More FTP (File Transfer Protocol) on our PLC. Using FTPGET and FTPPUT instructions we can transfer files to an FTP server. Our BRX Do-More PLC now has the ability to be an FTP Client. This will allow us to transfer our logged files to an FTP server that we programmed in the following post.
Data Logging – Video
As an FTP Client, the Do-More PLC now has the ability to transfer and retrieve files from the network at an appropriate time in the PLC logic.
We will be setting up a Windows 10 FTP server on our computer. Using the FTPPUT FTP Client command on our BRX Do-More PLC we will store a file on our FTP server. The FTPGET Client command instruction will be used to retrieve a recipe text file on our server. This recipe file will have three timers that we will be used in a sample program to turn on some outputs. Let’s get started.
The BRX Do-More PLC Peerlink Ethernet communication network is one of the easiest networks to set up and run. Peerlink is a shared programmable logic controller (PLC) common memory area within a local network. Do-More central processing units (CPUs) or DirectLogic PLC systems using ECOM100 modules can read the entire area and write to their programmed area if selected.
The network uses TCP/IP broadcast packets to publish the blocks of data PEERLINK (PL) memory to all of the devices attached. This broadcast will share the data network to the local domain only. Each member can optionally send data to the other members of the data-sharing network by electing to “publish” one or more blocks of PEERLINK (PL) memory.
This can sound confusing at first, but it is the simplest network to set up. You can have your Peerlink network up and running in a matter of minutes. We will be setting up and demonstrating the Peerlink network using a BRX BX-DM1E-18ED13 and the Do-More Simulator. Let’s get started.
Do-more plc modbus ascii protocol will be used to communicate to a Solo process temperature controller. A sample program will explain in detail how this is accomplished through a serial port.
Modbus is a communication method used for transmitting information over serial lines between electronic devices. The device requesting the information is called the Modbus Master (Client) and the devices supplying information are Modbus Slaves (Servers). This protocol was originally developed by Modicon systems.
Modbus protocol comes in basically three different types. Ethernet (Modbus TCP) or Serial (Modbus RTU or Modbus ASCII). Modbus TCP and Modbus RTU come as standard protocols in the BRX Do-More series of PLCs.
We will connect the BRX Do-More PLC to a Solo process temperature controller. This will be done using the Modbus ASCII protocol over serial RS485 communication wire. (Media) The present and set values (PV / SV) will be read from the Solo controller and the set value will be written when required. Let’s get started.
MQTT stands for Message Queuing Telemetry Transport. It is a simple publish and subscribe communication protocol that does not take too many resources.
Constrained devices with low bandwidth are ideal for MQTT. This protocol provides machine to machine (M2M) connectivity which is ideal for the Internet of Things (IoT) or Industrial Internet of Things. (IIoT)
We will be using a free on-line public MQTT broker from HiveMQ. Messages will be published and subscribed to by two clients. The first will be an MQTT Browser Client by HiveMQ. The Do-More Designer Simulator PLC will be the second MQTT Client. Information in the form of bits and words will be published and sent to both clients. Let’s get started.
The purpose of a ramp soak profile is to make gradual, controlled changes in temperature (Ramp), followed by a temperature hold (Soak) period.
We will be using our Do-More Proportional-Integral-Derivative PID Instruction with PWM output that we looked at last time to apply the ramp/soak profile. This will be done on the BRX Do-More PLC.
Using the immersion heater in a cup of water to keep the temperature at a constant value, we will be adjusting the profile of the temperature as we increase the setpoint (Ramp) and hold that set point for a predetermined time. (Soak) We will then decrease that temperature back to the original setting. (Ramp)
We will be modifying our existing program from our PID with PWM Output post. Let’s get started.
A Proportional-Integral-Derivative algorithm is a generic Control Loop feedback formula widely used in industrial control systems. A PID algorithm attempts to correct the error between a measured process variable and the desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly and rapidly, to keep the Error to a minimum.
Here are some references on PID control:
PID without a Ph.D. By Tim Wescott
Understanding PID in 4 minutes
PID Control – A brief introduction
PID Controllers Explained
Who Else Wants to Learn about On-Off and PID Control?
We will be using an immersion heater in a cup of water to keep the temperature at a constant value. Using the Do-More Designer software we will perform an autotune on our PID instruction.
Our immersion heater will be controlled through a relay using time proportional control from our PID output. Let’s get started!