Watchdog Timers Improve Safety and Reliability of Critical PLC-Controlled Systems

What is a Watchdog Timer?

A Watchdog Timer is a safety device that can be added to PLC- or computer-controlled systems to monitor normal operation and signal when a fault occurs. The hardware-based timers operate, independently of the control system and provide a simple, effective way to enhance operational safety and reliability.

When functioning correctly, the PLC continuously retriggers the watchdog timer. If a fault occurs in the logic hardware or software, the timer is not retriggered within the expected interval. The missed signal allows the waterdog relay timer to initiate a safety response, either by shutting down critical systems or alerting an operator.

Enhance System Protection with the TM2222

An example of a widely used Watchdog Timer for PLC is Regent Controls’ TM2222. This versatile product can be used as a Motion Control Timer or a One-Shot Timer by a simple switch setting, providing flexibility in diverse applications.

Compatible with a wide range of trigger sources, such as proximity sensors, limit switches, photoelectric controls, PLC output modules, the TM2222 is a smart safety solution for modern industrial environments.

Key Features of the TM2222 PLC Safety Timer

Additional benefits of the TM2222 watchdog timer include:

• Fully independent of the PLC or computer. No software required.
• Adjustable for any cycle rate or scan time. Fixed timing is also available.
• Models available for 120VAC and 24VDC control systems.
• Compact size, DIN rail or panel mount
• LED load and logic indicators
• Compatible with PLCs, sensors, solenoids, contactors, and more