For beginners, it is often necessary to practice and verify various PLC programs. If the input and output points are connected to the switches, buttons and other devices according to the conventional method every time, it is inevitable that they are cumbersome and troublesome. So I prefer to use the touch screen to simulate the debug PLC program, this method is simple and practical. For some programs, there are dozens or hundreds of input and output points. I believe most people can't find this kind of PLC so easily. And it is better to use the touch screen to call the inexhaustible soft elements in the PLC and to replace the input and output relays.
This method should also be desirable for the skilled person to adjust the PLC program, especially for the assignment of counters, timers, and registers. It is best not to use constants, but to use indirect registers. It is very convenient to modify at that time.
Please note that you do not need to have a touch screen in your hand to achieve this method, as long as you have a PLC, there is no limit to the number of points. What I'm talking about is a method called "online simulation". Just download a programming software. I recommend you to download the touch screen programming software EB500 of Shenzhen Step Electronics Co., Ltd. because this software is very easy to use.
Using this method, I made some courseware for your reference.
I believe that many people have encountered the program "8-stop trolley". Its calling principle is similar to that of an elevator. It is a program that beginners must read. Here I use the touch screen to simulate it all the way. As shown in the figure below, a moving element in the touch screen replaces the car. As long as there is a call signal, it will go straight to the target.
In the above interface, you can see that the speed of the trolley can be adjusted, and it is done in two ways. One is to adjust the motion interval, that is, the number of motion pixels in each step. The second is to adjust the time interval, which is the period of the oscillator. The smaller the period, the faster the movement.
After pressing the call button, the target data to be reached will be displayed in the "set position", the car will start to move, and the current data will be displayed in the "current position".
The movement principle of the simulated car: The "car" is composed of moving elements in the touch screen, which is controlled by the data register in the PLC. If the value of the X-axis register changes, it will move horizontally, and the Y-axis value will change. Vertical movement (not used here).
After the trolley arrives at a certain station, it is not stopped by the travel switch, which is different from reality. The actual situation is that we recorded the X-axis coordinate position of each station number in advance. If the X-axis register value of the trolley is equal to the X-axis value of a certain station number, it will stop.
In the same way, the call button of each station number has also undergone data processing. The following example illustrates its working process.
If the car is currently parked at the fourth stop (X-axis data is 270), and there is a call from the first stop (X-axis data is 90), through program comparison, 90 is less than 270, then the left-hand signal is output until the car reaches the destination stop.
The PLC program is written by Mitsubishi. If you have downloaded the EB500 software and have a Mitsubishi PLC in your hand, please leave your email address here and I will send both programs. The number of PLC points does not matter, because none of them are used in this program, they are all soft components.
In addition, I hope that when many experts come to this forum, they can write more realistic and weighty articles, or take up the projects they have experienced and designed, and explain them, so that more people can benefit and change Forum articles are empty and boring. Don’t you see such a phenomenon--someone chanted "I have a treasure book of sunflowers" in the front, and later generations flocked to it, and finally got the book, but the first page says "If you want to practice magical skills, swing a knife from the palace." , After you have made up your mind to come from the palace, the second page says "You can succeed without the palace", don't you say this is nonsense?
So blindly conservative precautions are meaningless. There is still a big gap between our country and the developed countries. It is ridiculous that we are conservative with each other.