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I recently came across a post in the forum titled“Can Microcontrollers Change the World?”. It frustrated me to no end. They keep saying they work in industrial control, but I really want to ask, have you ever been to a factory? Have you seen the industrial environment? Most likely, you’ve only seen it from the monitoring room.
Do you understand industrial protection levels? Do you understand redundancy systems? Do you know what is needed in the industrial field?
I strongly oppose anyone who thinks a microcontroller can replace a PLC in the industrial sector; you’ve clearly spent too much time in the lab and don’t realize there’s smog outside.
1. Let’s start with the basics, stability and reliability. Can the stability and reliability of a microcontroller compare to that of an IP67-rated product? Do you understand protection levels? Have you seen the harsh industrial scene? Have you seen outdoor equipment operations?
After a heavy rain, are you sure your microcontroller can still function? In winter, when temperatures drop below zero, can you guarantee it will still run? I don’t believe it.
2. In industries like automotive assembly lines or large power plants, there are often hundreds or even thousands of I/Os. Show me how you can use a microcontroller for that. Moreover, with PLCs being the heavy-duty equipment, you need to set up a redundancy system. Do you trust your microcontroller to be self-healing 100% of the time? If you can create a redundancy system with a microcontroller, I’ll respect you, but one thing is certain, the client will knock you out in seconds.
3. Control in the industrial field is just one part; data collection, communication, upper-level control, configuration, motion control, and display are also needed. All these require a complete industrial system and communication protocols. For instance, Siemens has a complete system that can achieve these functions. How do you plan to implement this with a microcontroller? How will you handle various Modbus, Profibus, Profinet, OPC, etc.?
4. Development cycle. PLC manufacturers are constantly improving their programming software to make it easier for engineers, and various program blocks are becoming more user-friendly. For example, PID modules, motion control modules, etc., greatly reduce the development pressure on engineers and shorten the development cycle. What about microcontrollers? Do you really think your self-developed solutions can outperform Siemens engineers?
This is something from a configuration software. How can a microcontroller achieve this? Do you expect one person to develop it? You’d be exhausted. In China, during bidding, there’s often a severe lack of time. PLCs, which are highly integrated and modular, often struggle against time constraints, while microcontroller development would probably take forever. Let alone supporting HMI, visual control systems, and the hundreds of brands and hardware drivers on the market. Even if you manage to create something, when faced with dozens of frequency converters, do you think that microcontroller can withstand the interference? In large projects, when a high-power motor starts, the entire power grid trembles. Wouldn’t the data from that microcontroller fluctuate wildly?
5. Distance issues. In the industrial field, sometimes cross-regional integration and monitoring are required. The communication methods often used are Ethernet (long communication distances) with repeaters or directly using civilian broadband fiber optics (sometimes distances can be several kilometers). The final solution might even involve using Microsoft’s Internet Explorer (yes, you heard right, Siemens WINCC WEB). Try supporting that with a microcontroller. Also, in emergencies or major accidents, if unattended, the PLC’s communication module needs to send messages to relevant personnel (like leaders) based on the situation. Can a microcontroller do that? How long would it take to develop?
After all this, I haven’t covered everything. I just can’t stand those who think microcontrollers can replace PLCs. Do you really think those AB systems in power plants worth hundreds of thousands or millions are useless?
Although most of the main control chips in PLCs are MCU microcontrollers.
The advantage of PLCs is that they can use ladder diagrams for secondary development. First, you must be clear: PLCs are meant for electrical engineers. Electrical engineers are not electronic engineers; their job is not just to consider how your MCU drives relays to control machine tools. Some electrical engineers may not even know C language or assembly language for MCU development (how would you expect them to work?). A few years ago, someone on 21ic said he would develop a new PLC using C language instead of ladder diagrams, but he vanished after a month or two on the forum.
Secondly, the advantage of PLCs lies in their strong stability. You might think it’s no big deal if an iPhone app crashes unexpectedly; just reopen it. If that fails, just restart it. But equipment in industrial settings cannot afford that; a second of downtime could cost a life…
So, if you want to use an MCU, relays, and optocouplers to make a PLC, you can, but without strict planning, design, debugging, testing, and various anti-interference tests, it can only be called a relay controller, not a true PLC that can be used in industrial settings. Generally, once industrial equipment is designed and tested, it won’t be modified. Future mass production follows the certified testing circuit and underlying program. Modifying any line of chip driver code requires re-certification.
A microcontroller is a component, while a PLC is a system composed of components and a large software suite. Asking whether the former can replace the latter is like asking: Can pork replace the wonton wrappers in a freezer?
Source: Xingke Source PLC Technology
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