Nail drill electronics. Motion, feedback and interaction.

01 / Architecture and sampling

Use a motor board and a controller as separable engineering blocks: the DRV8316 power stage handles three-phase switching; the MCU schedules PWM, ADC, SPI diagnostics and the foreground control loop. Their power, enable, fault and feedback nets should be reviewed as one system.

Sampling phase is part of the control design. Associate current samples with a defined PWM window, retain timestamps and detect missed schedules. A fast nominal loop is insufficient when sampling jitter or stale state enters the observer.

02 / Speed supervision and sensorless startup

The supervisor combines target speed, measured speed, observer lock, driver health and calibrated current limits. Evaluate faults before a zero-time-step early return so a repeated timestamp cannot suppress a newly arrived fault.

Sensorless operation needs a startup strategy: rotor alignment, controlled acceleration, observation handover and loss-of-lock handling. A running observer model and a speed PI module address parts of this problem; neither replaces the motor-specific startup process.

03 / Handpiece controls and user experience

The encoder path exposes raw quadrature counts and invalid-transition diagnostics. Define counts per detent and acceleration separately from RPM. Debounce pushbuttons and resolve single, double and triple clicks into explicit requests.

Keep stop and fault handling independent of the gesture timeout. Changing direction or operating mode should use the accepted motor state, rather than assuming a screen change has already changed the motor.

04 / Power path and cost decisions

Treat battery, charging, handpiece wiring and motor torque as whole-product decisions. Compare bus voltage, peak current, transient energy, capacitor ripple and connector geometry together. A lower-priced component can increase assembly or thermal cost.

At a 1,000-unit planning volume, reduce unique passive specifications, unnecessary inter-board connectors and assembly operations. Keep protection, motor feedback and repair access in the comparison instead of deleting them to reach a headline BOM price.

05 / Applications and reusable modules

Applications include nail-care handpieces, miniature polishers and controlled rotating instruments. Reusable modules include click decoding, speed supervision, fault priority, observation replay and sampling diagnostics. Motor parameters and mechanical interfaces determine the final product configuration.

Technical files and source downloads

Editable KiCad files, firmware, algorithms, BOM tables, interfaces and technical revision documents. The complete archive stores identical bytes once; historical ZIPs are expanded into .zip.contents folders. Its included restore.py reconstructs the technical file paths.

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