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Board Bring-Up Plan — SELV Spa-Light Switch Controller
Prerequisites
Use an isolated current-limited bench supply for SELV-side bring-up first. Do not connect 240 VAC until a qualified safety review and enclosure/layout review are complete.
1. Visual Inspection
- Confirm RAC03-05SK, F1, MOV1, U4, and mains connector are correctly oriented and isolated from SELV circuitry.
- Confirm no solder bridges on U1 UQFN and U2 SOT-23.
- Confirm supercapacitor C1 polarity/installation per final selected footprint.
2. SELV Power Rail Verification
Table
| Rail | Source | Expected | Measure At | Pass Criteria |
|---|---|---|---|---|
| +5V_ISO | PS1 output or bench-injected 5 V | 5.0 V | C2/C3 | 4.75-5.25 V |
| +5V_HOLD | D1/R2/C1 hold-up rail | ~4.7-5.0 V while powered | C1/U2 VI | Charges without excessive inrush |
| +3V3_MCU | U2 MCP1703A | 3.3 V | C5/U1 VDD | 3.20-3.40 V |
| 0V_ISO | SELV return | 0 V | U1 VSS | Common SELV return only |
3. Programming
- Connect PICkit-style ICSP header J5.
- Verify VDD target, VSS, MCLR_VPP, ICSPDAT, and ICSPCLK continuity.
- Read device ID before flashing firmware.
4. Functional Checks
Table
| Function | Stimulus | Expected Result |
|---|---|---|
| Buttons | Press SW1/SW2 | BTN_ONOFF/BTN_MODE transition low |
| Optical input | 40 kHz IR burst | OPTICAL_PROG_IN active-low pulses |
| Ambient light | Change light level | VEML7700 I2C reading changes |
| Temperature | Warm RT1 gently | TEMP_SENSE ADC changes monotonically |
| Mains-present | Lab-safe isolated test only | MAINS_PRESENT reflects optocoupler output |
| Relay outputs | Firmware pulse | RELAY_SET/RELAY_RESET drive low-side outputs briefly |
5. Safety Gate
Before any 240 VAC test: perform insulation/creepage review, verify primary component ratings, and use appropriate RCD/isolation/test equipment under qualified supervision.
Prerequisites
1. Visual Inspection
2. SELV Power Rail Verification
3. Programming
4. Functional Checks
5. Safety Gate
