Integration of PLC in IoT Applications
A few days ago, I received a message from a student, Xiao Wang. Their factory’s equipment is distributed across three different workshops, and every time a fault occurs, maintenance personnel have to run around to troubleshoot the issue. “Brother Wen, is there any way I can know the equipment status from my office, so I don’t have to run around all day?” Isn’t this a typical application scenario for the integration of PLC and IoT? Today, let’s discuss how this integration can achieve both remote monitoring and significantly reduce operational costs.
The core value of IoT + PLC lies in achieving “unmanned operation” and “preventive maintenance”, allowing machines to “speak” for themselves, actively informing you of their operational status and potential issues. Traditional factories require manual inspections, while this integrated application enables one engineer to monitor dozens or even hundreds of devices simultaneously, greatly improving efficiency.
The selection of IoT modules is the first critical step. For small and medium-sized enterprises with limited budgets, I recommend using cost-effective WiFi modules like ESP8266 or ESP32, which can easily achieve networking functionality at a cost of only a few dozen yuan. When connecting to PLCs, the most common method is through RS485/232 interfaces, using the Modbus protocol to read PLC data. The code implementation is actually quite simple:
void setup() {
Serial.begin(9600); // Initialize serial port for communication with PLC
WiFi.begin("Factory Network", "Password"); // Connect to factory WiFi
mqttClient.connect("Device ID", "Username", "Password"); // Connect to MQTT server
}
void loop() {
if (millis() - lastTime > 5000) { // Read PLC data every 5 seconds
readModbusData(); // Read PLC register data
sendToCloud(); // Send to cloud platform
lastTime = millis();
}
}
I once helped a food factory implement such a solution. Their chocolate cooling tunnel required strict temperature control, and originally, temperature had to be recorded manually every two hours. We connected an ESP32 module to the temperature control PLC to monitor temperature changes in real-time and upload the data to the cloud platform. The system was set up with temperature fluctuation alerts, and once the fluctuation exceeded ±2℃, it immediately pushed notifications to the technician via WeChat. After implementation, not only did we avoid three instances of product waste due to abnormal temperatures, but we also freed up two personnel originally responsible for inspections.
Data analysis is where the value lies. Collecting data is not the goal; uncovering the patterns behind the data creates value. The system I built for the client records all operational parameters of the equipment, and through simple algorithms, it discovers that a gradual increase in equipment power often indicates bearing wear. When an injection molding machine’s power increases by 15%, the system automatically alerts for maintenance, preventing a potential motor burnout incident and saving nearly 20,000 yuan in repair costs.
Safety issues must be taken seriously! Connecting IoT devices to industrial control systems is like opening a “door” to the factory. My advice is to adopt a one-way data transmission architecture, allowing only PLC data to be sent to the cloud, prohibiting direct control of the PLC from the cloud; use a separate network to strictly isolate IoT devices from the corporate office network; and regularly update firmware and passwords to prevent hacker intrusions.
Cost control also has its tricks. There is no need to build a complete system all at once; you can start with key devices, proving the value before gradually expanding. Some clients use Raspberry Pi as a gateway to connect multiple PLCs, saving 60% of costs compared to configuring IoT modules for each PLC individually. For data storage, you can start with the open-source combination of EMQX + InfluxDB + Grafana, which allows you to build a professional monitoring platform at almost zero cost.
Now, Xiao Wang’s factory system has been running for three months, and he told me: “Originally, two people were busy with maintenance, but now one person can handle it, and we have also detected several impending failures in advance, which has impressed the factory manager!”
If you want to get started with IoT + PLC applications, I recommend starting with a pilot project on a single device, mastering the basics before considering more complex systems. After all, digital transformation is a marathon, not a sprint.
