The conditions for self-learning PLCs should be as follows:
1, you have to learn programming software PLC (such as Siemens, Delta, Omron, etc.), each brand of PLC its programming software is slightly different, so what software to prepare what PLC.
2, it is best to reserve an HMI (Human Machine Interface), because PLC often needs to do some configuration control, it is really not good to achieve this, of course, now a lot of two in one, you can prepare a two-in-one device it is good.
3, a set of PLC programming software and HMI programming software
4. Relevant circuit design knowledge.
Although the total stop is pressed, the user program in the plc is still running, and when the condition is satisfied, the corresponding result is output according to the user control program and the external input condition.
Should not be a problem with plc itself, most of which is caused by an abnormal external input signal.
Start and stop the motor with a single button. It can be programmed by the working principle of PLC’s sequential scanning. The working process of PLC is simply
First, the input sampling phase. PLC sequentially scans the state of the input terminals and stores the state of each input point in the input image register.
Second, execute the user program. For the ladder diagram, it is scanned first, then, and from turned left to right. The state of each touch of contact needs to be logically operated with the result of the previous logical operation, and the result is stored in the component image register or the output image register.
Third, the output is refreshed. The state of each point in the output image register is sent to the output latch, and the output latches drives the load of each output relay through the output terminal.
There are numerous methods, and the counter can of course be realized, but I don’t think it is necessary to kill the chicken with a knife! Here I only give three examples of the S7-200 PLC. See below:
In the stepping program, the simpler way is to use the pause switch as the normally closed one as the next trigger condition in the stepping program, and the other trigger conditions are connected in series, but only if it is done at each step. Pause, not stop where you want to stop