Many technologies that we use today are becoming outdated meaning that we won’t use it anymore because of new tech. When it comes to programmable logic controllers, they will be here for a longer period of time because we are constantly improving machines in the industry and controllers which is the main part of these machines in order for them to work properly.
If you want to become a PLC programmer you should first know the hardware of it, so it will be easier to understand how they work. It isn’t very easy to find someone who can teach you locally, so it is better to find a professional online. There are many tutors that can help you, but the might be expensive, so something like tutorials is a better option.
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PLC is the most important part of machines because it regulates its actions. It connects with sensors and processes the information in order to make the next move which is programmed before it is connected to the machine. Besides sensors, input devices can be connected. Depending on the outputs and inputs, it can record and monitor run-time information like start and stop processes, operating temperature, and productivity.
You can compare them to computers, just stronger, and can last 10 years without replacing any parts. It isn’t meant to work with a large amount of information or complex tasks. Usually, one controller is for one machine. It isn’t very good at writing and reading databases. Because they are smaller and usually don’t have a display, it is harder for the worker to check data. Read more on this page.
Example of PLC
The best way to learn to use it is by practice. For example, overhead crane needs a controller. There are simple buttons like down, up, left, and right that an operator has in the control box. The PLC function is to send the information to the motor to move the crane in a direction where the operator wants. The function is the same for each button.
It may sound simple, but there are a lot of things you should consider. For example, if it takes a long time for the crane to move from one position to the other, the worker has to push the button for that amount of time which can hurt and isn’t safe. The solution here is to program it so the crane will move constantly until the button is pushed again. Again, there are situations where worker forgets to push the button again and we have a problem to stop it. There are a lot of safety procedures you have to follow in order to have great code.
The solution for safety procedures is adding sensors that will tell the crane to stop if someone walks in the operational area. There would be buttons around the place that will stop it when pushed which will be used by workers that can detect a problem when it is about to happen. You also have to ad limits to where the crane can go in the program. Alarms need to be added for a situation when a disaster occurs. This isn’t hard to program, you just have to follow certain procedures.
There are two main signals that PLCs and write and read, analog and digital. Analog signals are more complex and they are used for level, temperature, pressure etc. Digital signals have two possibilities, yes or no, 1 or 0. So when we have a switch, when we turn it on or off, we are using digital signals also called discrete. The input and output of this switch are both digital signals.
The important thing to know is that digital signals or bits can be used in many ways because for each function they send a pulse. Pulses can be counted for many reasons and you can determine which action is going to happen after 3, 4 or how many pulses you want. When creating your own functions, you can use a timer that will turn the motor on for a certain amount of second.
Nowadays, most of the machines have both types of signals. With analog signals, we are determining in what conditions discrete signals will work. You can measure the efficiency of a motor, but you need to have the right equipment that will do the measuring that will be sent to the PLC. It is very important to do this correctly because you will be working with things like pressure, the temperature which can be crucial for the overall operation.
A great thing about PLCs is that they are expanding very fast and as the technology develops we will be able to do complex tasks much easier. A normal PLC has a process which has main memory, CPU, and sometimes interface and communications capability. Inputs and outputs or I/O, and the number depend on the model. They have a power supply, chassis, and a programming tool.
The connection between the system and the reality are I/O cards. Digital can differ in voltage, for example, an analog can differ in more aspects. There are remote and local cards. You can locate remote I/O in a different location than the processor if it is suitable for that position. Local is always in the chassis where the processor is. We know that in the near future we won’t need communication tools like these. Everything will be in a single card that can send the information, so the wiring can be reduced to the minimum.
The traditional system used in PLCs is called Relay Ladder Logic or just Ladder Logic. It is very easy for professionals to understand and read. PLCs are primary replacements for a large number of relays. The design is meant to be easy for technicians to troubleshoot or analyze. If you have some knowledge in elementary electrical circuits, it won’t be hard for you to program PLCs. It basically converts inputs into outputs.