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Just arrived at the workshop this morning, and the equipment suddenly alarmed and stopped. Checking the fault information: Timer overflow. Our colleague Xiao Zhang scratched his head: “Isn’t it just a timer? Why does it keep having problems?” Many beginners in industrial control encounter similar situations. Today, I will guide you to thoroughly master the efficient application of timers in industrial control systems, making your programs more stable and responsive.
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Timer: The “Pacemaker” of Industrial Control Systems
A timer is like our alarm clock, triggering specific actions at preset times. In microcontroller systems, it achieves precise timing through hardware counting; in PLCs, it appears in the form of instructions, such as TON (On Delay Timer), TOF (Off Delay Timer), etc. The core value of a timer is to allow the system to execute the “right action” at the “right time”. Without timers, there is no sense of rhythm, and the entire industrial automation system will fall into chaos.
I remember when I first started, I was responsible for the renovation of a packaging line. The conveyor belt needed to stop precisely for 0.5 seconds for the robotic arm to grab the product, but it was always unstable. It turned out that the timer was misapplied: the timer value was being reloaded every scan cycle, leading to inaccurate timing. This is a common mistake made by many beginners.
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Three Timer Modes to Solve 90% of Industrial Control Needs
In practical applications, timers mainly have three working modes: single trigger, periodic trigger, and delay trigger.
Single trigger is suitable for starting sequences, one-time operations, etc. For example, after pressing the start button, the system needs to sequentially turn on the hydraulic pump, main motor, and auxiliary equipment. Code example (microcontroller):
if(start_flag && !timer_running){timer_start(TIMER1, 1000); // Start timer, 1000mstimer_running = 1; // Mark timer as started}
Periodic trigger is the most commonly used mode, suitable for tasks that need to be executed at a fixed frequency, such as data collection and status monitoring. An efficient periodic timer should adopt a “flag-triggered + main loop detection” structure, rather than executing complex operations directly in the interrupt:
// Timer interrupt functionvoid TIMER0_IRQHandler(void){data_sample_flag = 1; // Only set the flag} // Main loopwhile(1){if(data_sample_flag){SampleData(); // Execute data collectiondata_sample_flag = 0;}// Other tasks}
Delay trigger is used for operations that need to wait for a period before execution, such as checking whether the motor reaches the rated speed 5 seconds after starting. This can be implemented in PLC as follows:
LD X0 // Start signalTON T1, K50 // 5 seconds delay timer (K50 represents 50 counts of 100ms)LD T1 // Timer completedOUT Y1 // Start detection program
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Four Timer Optimization Techniques to Enhance System Stability
Optimization Technique 1: Avoid timer nesting. I have seen a system crash because a timer interrupt called another timer, leading to stack overflow. The correct approach is to manage multiple timer tasks uniformly, using a state machine or task table to achieve a clear structure.
Optimization Technique 2: Set priorities reasonably. Critical control timers (such as safety monitoring) should be set to a higher interrupt priority. Non-urgent tasks (such as data logging) can be set to a lower priority.
Optimization Technique 3: Use software timers to reduce hardware pressure. For tasks that do not require high precision, a hardware timer can be used as a reference to implement multiple software timers through counting:
if(++counter1 >= 10) { // Execute every 10mscounter1 = 0;// Execute task 1}if(++counter2 >= 100) { // Execute every 100mscounter2 = 0;// Execute task 2}
Optimization Technique 4: Add a watchdog. The industrial environment is complex, and electromagnetic interference may cause the program to run away. Using timers in conjunction with a watchdog can automatically reset the system in case of anomalies.
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Practical Experience: Insights from Production Line Renovation
Last year, we renovated an old production line, where the original system was sluggish and frequently crashed. Analysis revealed that the main issue was improper timer handling: the key panel button handling, sensor data collection, and motor control were all crammed into the same timer interrupt, leading to task backlog.
During the renovation, we distributed tasks across timers of different priorities, using hardware timers for critical control and software counting for non-critical tasks. The system stability immediately improved, with downtime reduced from 3-4 times a week to almost zero.
Remember, the application of timers in industrial control systems is not about being “fast”, but about being “stable”. It is better to sacrifice a bit of response speed to ensure the reliability and determinism of the system. Next, try to refactor the timer structure of your current project, and you will find a qualitative improvement in system stability. If you have any questions, feel free to leave a comment, and I will delve deeper into advanced timer applications in future articles.
