Temperature and Humidity Sensor Node Design

flux

I continued until ACUs became unavailable. Completed: renamed/described the project, selected the architecture and parts, built the schematic with USB‑C input, TPS2595 eFuse protection, MP28301 3.3 V buck, ESP32‑C3 Wi‑Fi/BLE module, SHT41 sensor, USB data ESD, boot/reset, status LED, and created project files for the spec, power budget, firmware starter, bring-up plan, and regulatory notes.
Remaining work:
  • Re-run ERC after the last cleanup step and resolve any remaining warnings.
  • Confirm no-connect markings were applied for unused ESP32/J1 pins.
  • Perform PCB placement/routing, especially ESP32 antenna keepout, buck layout, USB routing, and sensor thermal isolation.
  • Run DRC/airwire checks after layout.
  • Validate final TPS2595/MP28301 settings against datasheets before manufacturing.
A

angierg27

continue

flux

I’ll inspect the current schematic and project docs, run design checks, then fix any schematic issues I find before summarizing what remains for layout.

flux

I’m blocked because the account has no available ACUs, so I can’t continue AI layout actions right now.
Completed this session:
  • Verified the schematic/ERC state: no open errors or warnings were reported.
  • Set up the PCB as a 45 mm × 30 mm rounded rectangle with a standard 4-layer stackup and 0.5 mm board keepout.
  • Confirmed the board area is workable, though routing may be tight around the ESP32/power section.
Remaining work:
  • Place components with ESP32 antenna keepout, USB-C edge placement, compact buck/eFuse layout, and isolated SHT41 placement.
  • Route the PCB.
  • Run DRC and airwire checks.
  • Fix any routing or layout violations before manufacturing export.
Review placement constraints
Check ACU balance
Run layout checks
Estimate board size
Sign up to send

Files

Schematic

Layout

Preview

Project Specification — USB-C WiFi BLE Environmental Sensor Node
Purpose
Consumer USB-C powered environmental node measuring temperature and relative humidity, reporting over Wi-Fi and supporting BLE provisioning.
Key Requirements
  • USB-C receptacle, 5 V sink/default supply.
  • Design must tolerate common 0.5 A to 3 A USB-C sources, but normal product current is limited for default-current compatibility.
  • Include reverse-current/OVP/UVLO/OCP/inrush protection.
  • Wireless: 2.4 GHz 802.11 b/g/n and BLE 5.x.
  • Digital temperature/RH sensor.
  • Low-power firmware strategy despite USB power.
  • Consumer product regulatory planning.
Architecture Decisions

Table

BlockDecisionRationale
MCU/radioESP32-C3-WROOM-02-N4Lower power/cost than ESP32-S3, integrated antenna, Wi-Fi b/g/n + BLE 5.x, native USB Serial/JTAG.
SensorSensirion SHT41-AD1B-R3Accurate I2C temperature/RH sensor with low-power operation.
USB-CSink-only Rd pulldowns on CC1/CC2Simple 5 V USB-C input without PD complexity.
Input protectionTPS259530 eFuseProgrammable current limit, UVLO, inrush control, reverse-current/OVP-class protection.
3.3 V supplyMP28301 low-IQ buckBetter thermal/efficiency margin than LDO for Wi-Fi bursts.
Electrical Interfaces
  • USB D−: ESP32-C3 IO18 via USBLC6 ESD array.
  • USB D+: ESP32-C3 IO19 via USBLC6 ESD array.
  • I2C SDA: ESP32-C3 IO4 with 4.7 kΩ pull-up.
  • I2C SCL: ESP32-C3 IO5 with 4.7 kΩ pull-up.
  • Status LED: ESP32-C3 IO7 through 1 kΩ.
  • BOOT: GPIO9 with 10 kΩ pull-up and button to GND.
  • GPIO8: 10 kΩ pull-up for joint USB/UART download mode.
  • GPIO2: 10 kΩ pull-up for ESP32-C3 boot recommendation.
  • EN: 10 kΩ pull-up, 1 µF RC delay, reset button to GND.
Layout Requirements
  • Place ESP32 module antenna at board edge with manufacturer antenna keepout; no copper under antenna on any layer.
  • Place SHT41 away from MCU, buck regulator, USB connector metal, LEDs, and other heat sources; add enclosure ventilation.
  • Place USB ESD array close to connector.
  • Keep buck VIN/SW/inductor/output-cap loop compact with solid ground return.
  • Put eFuse support parts close to U3 pins.
Open Items
  • PCB placement/routing not yet performed.
  • Final current limit, thermal behavior, and RF performance must be validated on prototype.
  • Regulatory documentation must be completed with final layout, test reports, and module grant/labeling evidence.

  • Purpose

  • Key Requirements

  • Architecture Decisions

  • Electrical Interfaces

  • Layout Requirements

  • Open Items