RF Watchdog / Signal Loss Timeout
An RF watchdog is a counter that runs continuously in the receiver and is reset on every valid packet. If no valid packet arrives for the defined period, the counter expires and the outputs are taken to a safe state. On the HCT402 set this period is defined as 250 ms; when it expires the motor goes to the safe centre position and oil flow stops.
A wireless link is intermittent by design: packets arrive at certain intervals and some are lost to interference. The watchdog period is chosen between these two realities.
- If chosen too short: the system stops unnecessarily on normal packet losses and motion becomes jerky.
- If chosen too long: motion continues dangerously after the operator releases the remote control or goes out of range.
- Correct behaviour: when the period expires, go to the defined safe state rather than maintaining the last command.
What the safe state is varies with the application: in hydraulic lever control the valve returning to the centre position and oil flow being cut, in crane control the motion outputs being released. The machine stopping on loss of signal in wireless control is also the behaviour expected in the relevant European standards for lifting machinery. On the AXI side, the 250 ms timeout of the HCT402 is the concrete counterpart of this logic.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety