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Safety Analysis — SELV Spa-Light Switch Controller
Status
Draft design-stage safety analysis.
Applicable Standards to Review
- AS/NZS 3100
- AS/NZS 3820
- AS/NZS 3000
- AS/NZS 60529 / IP67
- AS/NZS 60669 where applicable
- AS/NZS 60335.2.60 if classified as spa/whirlpool equipment
- IEC/EN 60335-1 and IEC/EN 62368-1 evidence for the isolated PSU module
Hazard Summary
Table
| Hazard | Source | Mitigation in Schematic | Open Item |
|---|---|---|---|
| Electric shock | 240 VAC input | Certified isolated RACM06E-12SK/277 PSU baseline, SELV-only controls, visible PCB isolation corridor | Layout creepage/clearance and safety engineer review required |
| Surge/transient | AC mains | Fuse F1 and MOV1 | Confirm fuse type/rating and MOV coordination |
| False programming | Ambient/pool lighting | 40 kHz IR receiver, firmware preamble/timeout requirement | Firmware validation through sealed optical port |
| Overtemperature | Sealed IP67 enclosure | NTC divider TEMP_SENSE | Define trip threshold after thermal testing |
| Unsafe relay state | Reset/brownout/invalid command | Firmware default relay OFF, single RELAY_DRIVE GPIO controlling Omron G2RL-2A-DC12 relay coil | Firmware implementation and watchdog tests |
| Power interruption | Mains loss | MAINS_PRESENT opto and supercap hold-up | Verify hold-up with measured current |
Isolation Boundary
Primary-side / mains-switching nets: MAINS_L_IN, MAINS_L_FUSED, MAINS_N, LOAD_L_OUT, LOAD_N_OUT, PE_CHASSIS, MAINS_SENSE_LIMIT, MAINS_SENSE_IN. SELV-side nets: +12V_RELAY, +5V_ISO, +5V_HOLD, +3V3_MCU, 0V_ISO, RELAY_DRIVE, and all user I/O. The FODM214 optocoupler, RACM06E-12SK/277 PSU, and relay coil/contact isolation inside K1 cross or bridge the isolation boundary and must be verified against datasheets and layout geometry.
PCB Isolation / Creepage Placement Notes
- PCB placement now includes visible top-side zone markings: MAINS / SWITCHED 240 VAC zone, 8 mm isolation / no-copper corridor, and SELV control zone.
- Mains input/protection/relay/output components were placed on the left side; MCU, optical receiver, sensors, buttons, LEDs, programming connector, and low-voltage regulators were placed on the right SELV side.
- Final routing must enforce no SELV copper, fills, stitching vias, or plane copper inside the isolation corridor except through certified isolation components.
- Verify actual creepage/clearance on final routed layout around PS2, U4, K1 coil/contact separation, J1, J6, F1, MOV1, and mains sense resistors.
- Current placement is not a safety approval; qualified safety engineering review is still required before energizing or manufacturing.
Required Before Mains Energization
- Qualified electrical safety review.
- Accredited lab compliance plan for Australian sale/use.
- PCB layout creepage/clearance review, including confirmation that inner ground/power planes are split/kept out across the isolation corridor.
- Enclosure/IP67 optical port validation.
- Confirm relay/contactor stage is 2-pole mains-rated and reviewed separately.
Status
Applicable Standards to Review
Hazard Summary
Isolation Boundary
PCB Isolation / Creepage Placement Notes
Required Before Mains Energization
