The Productivity Suite Software allows us to use tags in the PLC. Tags are a method for assigning and referencing memory locations (numbering systems) within the programmable logic controller. They allow a more structured programming approach and are stored within a tag database. The tag database is stored in the memory of the Productivity Series of PLCs from Automation Direct. Do not overthink tags. Tags are just names assigned to variables of any data type stored in the PLC memory.
We will now look at the tag numbering systems and database used with the Productivity 2000 controller. Let’s get started. Keep on Reading!
Traffic lights are used just about everywhere on busy roads around the world. They can help prevent traffic accidents and keep traffic flowing smoothly in the right direction by regulating the flow of cars, trucks, and other vehicles. The most common traffic light uses red, yellow, and green lights, along with arrows or flashes to indicate which lane should proceed when the lights change from green to yellow or red. Now you can visually see the 4-way traffic light by using the EasyPLC software suite. This provides an easy way of learning PLC programming.
Using the five steps for PLC program development, we will discuss how to program this traffic light. Four traffic lights and pedestrian panels with push buttons will be used. We will be using an Automation Direct Click PLC for this application, but the general methods can be used for any PLC. Let’s get started. Keep on Reading!
We will be using an MQTT broker in Node-RED to communicate to the productivity PLC clients. MQTT stands for Message Queuing Telemetry Transport. This simple ‘publish and subscribe’ communication protocol does not take too many resources.
Constrained devices with low bandwidth are ideal for MQTT. This protocol provides machine-to-machine (M2M) connectivity, perfect for the Internet of Things. (IoT) This protocol is not for remote IO or real-time (deterministic) applications. MQTT is a good solution for applications that move data from hundreds or thousands of machines (sensors) to clients in many networks.
We will be installing and programming the AEDES MQTT Broker in Node-RED. A productivity P2000, P1000, and Node-RED will be the clients communicating to the broker. The PLC simulator inputs on each controller will control the outputs on the other controller. This will demonstrate the communication capability for publishing and subscribing to this IoT platform. Let’s get started. Continue Reading!
The Productivity Suite Software allows us to modify our existing program and execute the new code without stopping the scanning of the PLC. This is referred to as online programming or editing. We change the ladder logic code and when we save it to the PLC, the current scan of the PLC is held until the new code is written into the unit. It then releases the scan and our new program starts to execute. This happens in milliseconds so our process can continue to operate.
We will be taking our existing Start / Stop circuit from last time and add a Jog input using online programming. Changing the program online is a common method of programming. The documentation will also be changed during this online program change. Let’s get started. Keep on Reading!
The Machine Simulator (MS) is part of the EasyPLC software suite. It has many built-in machines that are used to show different programming techniques. The robotic cell example is one of these machines. This will demonstrate a sequencer example. In this case, an engine is lifted and placed onto a rack. The logic will step through various steps to perform the task.
We will be using a BRX Do-More PLC and the Do-More Designer programming software to program this EasyPLC machine simulator engine loader of the robotic cell. This will be done using Modbus TCP (Ethernet) for communications. The program will allow you to start, stop and jog the sequencer. Modifications of the EasyPLC Robotic Cell will include controls for this operation. Using the five steps for program development, we will show how this sequencer is programmed. Let’s get started. Keep on Reading!
The Do-More Designer Programming Software (2.9) or higher includes a Modbus I/O Scanner with some profiles for Modbus Server (Slave) devices. This will greatly reduce the time it takes to implement and troubleshoot communications in your projects. Modbus communications are done independent of the PLC scan time and will have little or no ladder logic for the program.
Last time we communicated to a Solo process temperature controller via Modbus RTU RS485. (twisted pair) We manually set the Modbus IO scanner, reading the present value (PV) and set value (SV) of the Solo. The writing of the set value (SV) located within the BRX Do-More controller was also done. This was all be done without using any ladder logic code. We will now use the Modbus profile in the Modbus IO Scanner to connect a Click Plus PLC to our RS485 network. Using the Modbus scanner to write and read instructions we will also show how to use the ladder logic code with our scanner. Let’s get started. Continue Reading!