Temperature and Humidity Sensor Node Design

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Work Completed
  • Project description and system architecture updated
  • Removed legacy power and level-shifter ICs: U2, U3, U7
  • Added and configured major ICs:
    • U8 (5 V eFuse with OVP/UVLO)
    • U9 (3.3 V synchronous buck)
    • U10 (74AHCT125 SPI up-shift buffer)
    • U11 (74LVC1G125 MISO down-shift buffer)
  • Added passive support:
    • Bulk capacitors on rails: C6, C7
    • Decoupling capacitors near ICs: C8, C9, C10, C11, C12
    • Series resistors on SPI: R5, R6, R7
    • Pull-up resistors on SPI: R8, R9, R10, R11
  • Connected major nets:
    • U8 IN→J1:VBUS, OUT→5 V rail
    • U9 VIN→5 V rail, VOUT→3.3 V rail
    • U6 VDD→5 V rail
Remaining Tasks
  • Complete net connections for passives:
    • Tie [C6]–[C12] to appropriate rails
    • Route SPI up/down-shifters ([U10], [U11], plus R5–R7 series) and pull-ups
  • Review schematic for correct connectivity and decoupling placement
  • Prepare PCB layout:
    • Set 4-layer stackup
    • Define net classes (power, SPI, I2S, I2C, ADC-hiZ)
    • Create antenna and noisy-return keepout zones
  • Establish layout rules (trace widths, impedance, clearances)
Success Criteria Status
  • Power tree ICs and decoupling: ✅ major devices added; passive connections pending
  • SPI interface: ✅ robust buffers and series resistors in place; routing pending
  • PCB layout preparation: ⏳ not yet configured
Next Step Continue with detailed net wiring for capacitors and level-shifter passives, then perform a schematic review before moving on to PCB stackup and net-class definition.
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USB-C Powered Arduino Nano ESP32 Soil Monitor with Protected 5 V Rail, Integrated eFuse (OVP/UVLO), 3.3 V Synchronous Buck, SPI Level Shifting, and Optimized 4-Layer Layout

Properties

U

USB C

Arduino

creativecommons.org/licenses/by/4.0/

Display

WiFi

Agriculture

5

V

5

USB

USB_C_VBUS --> EFuse_OVP_UVLO --> V5_Rail --> V3_3_Buck --> V3_3_Rail; V5_Rail --> MAX98357A; ESP32_Nano -->|I2C| OLED, AHT20; ESP32_Nano -->|I2S| MAX98357A; ESP32_Nano -->|SPI| A74AHCT125 --> B74LVC1G125 --> MicroSD; ESP32_Nano -->|ADC| RC_Filter --> Soil_Sensor

Pricing & Availability

Distributor

Qty 1

Arrow

$21.99–$23.82

Digi-Key

$25.34–$26.39

LCSC

$34.99–$35.16

Mouser

$30.39

TME

$2.29

Verical

$23.66–$33.28

Controls