Industrial computers may run unattended for long periods, making predictable recovery from software hangs an important design requirement. A watchdog timer can detect when expected software activity stops and trigger a configured recovery action. It is a useful resilience mechanism, but it should be designed and tested as part of the full control system.
Hardware and software watchdogs
A hardware watchdog is implemented in a platform component or dedicated circuit and can act even when the operating system is no longer responsive. A software watchdog may monitor processes or system health but can be less effective if the kernel or entire system is frozen. Confirm the implementation on the selected motherboard; the term “watchdog support” can refer to different capabilities.
Choose meaningful health checks
A watchdog should not be refreshed merely because a timer thread is still running. The application should confirm that essential work is progressing, critical services are responsive, and required I/O checks have completed. Otherwise, a partially failed system may continue feeding the watchdog without delivering useful control.
Define the recovery action
Depending on the platform, expiry may trigger a reset or another supported action. Document what happens to connected equipment, unsaved data, outputs, and network sessions. A reboot is not a substitute for a safety-rated shutdown or independent interlock where people or equipment could be at risk.
Test failure modes deliberately
In a safe test environment, simulate application deadlock, service failure, resource exhaustion, and loss of communication. Verify timeout, recovery behavior, restart sequence, logging, and time to return to service. Also test planned maintenance and software updates so normal long-running operations do not trigger false resets.
Implementation checklist
- Verify motherboard, firmware, driver, and OS watchdog support.
- Select a timeout appropriate to the process’s legitimate worst-case delay.
- Refresh only after meaningful health checks succeed.
- Log watchdog events and investigate repeated resets.
- Provide independent safety controls wherever the risk assessment requires them.
A well-designed watchdog improves recoverability and helps reduce some forms of downtime. The reliable approach combines verified hardware support, thoughtful software health checks, safe recovery behavior, and documented fault-injection testing.
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