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Schematic

Layout

Preview

U6
U1
U5 LCD
Manufacturer Part Number
NHD-C0216CIZ-FSW-FBW-3V3
R13
Resistance
220kΩ
R19
Resistance
10kΩ
R17
Resistance
10kΩ
R5
Resistance
10kΩ
R8
Resistance
10kΩ
R6
Resistance
1kΩ
R16
Resistance
100kΩ
R1
Resistance
470Ω
R4
Resistance
10kΩ
R2
Resistance
10Ω
R10
Resistance
4.7kΩ
R18
Resistance
10kΩ
R12
Resistance
220kΩ
R9
Resistance
10kΩ
R15
Resistance
100Ω
R7
Resistance
10kΩ
R11
Resistance
4.7kΩ
R3
Resistance
10kΩ
F1
Button ON_OFF
C12
Capacitance
2.2uF
C4
Capacitance
1uF
C14
Capacitance
100nF
C15
Capacitance
100nF
C18
Capacitance
10nF
Button Plus
C9
Capacitance
100nF
C16
Capacitance
100nF
Button Minus
C13
Capacitance
10uF
C8
Capacitance
100nF
C2
Capacitance
10uF
C5
Capacitance
1uF
C17
Capacitance
10nF
C3
Capacitance
100nF
C6
Capacitance
100nF
C11
Capacitance
10nF
C7
Capacitance
10nF
Button Col
C10
Capacitance
10nF
U4
LED1
U7
Manufacturer Part Number
RV-3028-C7 32.768KHZ 1PPM-TA-QC
J1 AC Mains In
J6-AC Mains Out
J5
U2
D2
PS1
MOV1
D1
Q2
L1
Inductance
4.7 µH
C1
Capacitance
1 F
RT1
K1-Relay
U5-Light Sensor
J2 -CR2032 Holder
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

RailSourceExpectedMeasure AtPass Criteria
+5V_ISOPS1 output or bench-injected 5 V5.0 VC2/C34.75-5.25 V
+5V_HOLDD1/R2/C1 hold-up rail~4.7-5.0 V while poweredC1/U2 VICharges without excessive inrush
+3V3_MCUU2 MCP1703A3.3 VC5/U1 VDD3.20-3.40 V
0V_ISOSELV return0 VU1 VSSCommon 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

FunctionStimulusExpected Result
ButtonsPress SW1/SW2BTN_ONOFF/BTN_MODE transition low
Optical input40 kHz IR burstOPTICAL_PROG_IN active-low pulses
Ambient lightChange light levelVEML7700 I2C reading changes
TemperatureWarm RT1 gentlyTEMP_SENSE ADC changes monotonically
Mains-presentLab-safe isolated test onlyMAINS_PRESENT reflects optocoupler output
Relay outputsFirmware pulseRELAY_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