Ceiling Fan Controller Power-Fail Recovery: State, Safety and UX

Engineering note. This guide is published by the Sankey engineering content team for OEM planning. It explains the design decisions and evidence a project team should review; component datasheets, the intended end product, target-market requirements, and controlled laboratory testing remain the source of truth for a released design.

Power recovery is a product behavior, not a final firmware preference. After a supply interruption, the controller must make a defined decision about motor restart, direction, speed, light state, remote pairing, and incomplete nonvolatile-memory writes.

What this decision changes

The recovery policy affects customer expectations, safety analysis, motor stress, firmware state design, remote-control behavior, service calls, and the test conditions that must be included before release.

Start with measurable inputs

Define likely outage duration, brownout profile, supply ramp, required restart behavior, stored speed and direction, light behavior, local and remote controls, safety restrictions, and whether the product may restart unattended in its installed environment.

Engineering review method

Write recovery states before implementing firmware. Separate a clean shutdown from a brownout, validate voltage-monitor thresholds, ensure that configuration writes are atomic or recoverable, and test power interruptions at start, run, speed change, remote command, and memory-update conditions.

Evidence to keep with the design

Keep the state diagram, supply interruption profiles, brownout threshold data, reboot log, stored-state checks, motor and light response observations, firmware version, and the criteria used to declare recovery successful.

Failure paths to challenge early

Failures include restarting at an unsafe or unexpected state, corrupting stored settings, repeatedly rebooting near a marginal supply, accepting a remote command before the control state is valid, or treating a short dip and a long outage as the same event.

Before prototype release

Document the customer-visible policy and test it with the representative motor, light load, receiver, and supply. Revalidate after any change to power supply, microcontroller, nonvolatile storage, reset circuit, or control software.

Questions an OEM team should close

Which states are restored, which are reset, and why?
What supply interruption profiles have been tested at the most sensitive operating states?
How is incomplete configuration storage detected and recovered?