What is a watchdog timer in a PLC, and what is its purpose?
A watchdog timer is a crucial safety feature in Programmable Logic Controllers (PLCs) that monitors the control program to detect potential software or hardware malfunctions that could cause the PLC to freeze or enter an infinite loop.
Essentially, the watchdog timer is a hardware timer that the control program must periodically reset during normal operation. If the program fails to reset the timer within a set interval, the watchdog timer interprets this as a potential error. When this happens, the watchdog initiates a predetermined response, such as a system reset or a shift into a safe state.
This mechanism prevents the PLC from remaining in an undesirable state, reducing risks of equipment damage or safety hazards in critical applications. By ensuring that the control program executes within the specified time, the watchdog timer enhances the reliability and safety of the entire PLC system.