USB-C Temperature-Humidity Sensor Node Design
Worked for 12 mins 17 sec
Built the schematic for a USB-C powered Wi‑Fi/BLE temperature-humidity node and captured the requirements in project files.
Completed:
- Renamed the project to USB-C WiFi BLE Environmental Sensor and updated the description.
- Created the Project Specification.
- Selected and added the main parts:
- ESP32-C3-WROOM-02-N4 Wi‑Fi/BLE module
- SHT41 I2C temperature/humidity sensor
- USB-C 2.0 receptacle
- TPS259530 eFuse input protection
- AP63203 fixed 3.3 V buck regulator
- USBLC6 USB ESD protection
- BOOT/RESET buttons and status LED
- Wired the schematic blocks:
- USB-C VBUS, GND, CC1/CC2 5.1 kΩ sink pull-downs
- eFuse input protection with UVLO/current-limit/soft-start passives
- 5 V protected rail to 3.3 V buck regulator
- ESP32-C3 power, EN reset RC, BOOT GPIO9, GPIO2 boot pull-up
- Native USB D+/D− to ESP32-C3 GPIO19/GPIO18 with ESD protection
- SHT41 I2C bus with pull-ups and local decoupling
- Low-current status LED
- Consulted datasheets for ESP32-C3, SHT41, USB-C connector, TPS2595, and AP63203.
- Created the Firmware Starter — ESP32-C3-WROOM-02-N4 with PlatformIO Arduino code and the actual pin map.
Validation status:
- Schematic ERC-specific checks returned clean for the queried ERC categories.
- Full review still reports expected pre-layout airwire/DRC errors because the PCB has not been placed or routed.
- Full review also reports missing MPNs for generic passives, which should be resolved before manufacturing by selecting real resistor/capacitor/inductor part numbers.
Remaining work:
- Assign real manufacturer part numbers for all generic passives and the LED.
- Run a final full schematic review after MPN cleanup.
- Move to PCB layout: set board size, place components, keep ESP32 antenna at the board edge with keepout, place SHT41 away from heat sources, then route and re-run DRC.
Assign MPNs
Run schematic review
Set board dimensions
Auto-place components
Add mounting holes
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Project Specification
Project Overview
Status: Draft.
USB-C powered consumer environmental sensor node measuring temperature and relative humidity, with dual-radio 2.4 GHz Wi-Fi 802.11 b/g/n and BLE 5.x connectivity. The design targets low-power operation while powered from USB-C 5 V default sources.
Intended Use
Indoor consumer environmental monitoring node powered by a USB-C cable from a charger, host port, or power bank. Intended as a compact production-oriented prototype with SMD assembly and an RF module to avoid custom RF matching.
What the Device Should Do
- Measure ambient temperature and relative humidity using a digital sensor.
- Communicate over Wi-Fi and Bluetooth Low Energy.
- Power from USB-C 5 V default sink mode.
- Protect the input against reverse/over-voltage/under-voltage/over-current conditions.
- Support USB-C sources from 0.5 A to 3 A without assuming 3 A availability.
- Provide boot/reset access and firmware bring-up path.
Main Features
- ESP32-class Wi-Fi/BLE MCU module with integrated antenna.
- Digital I2C temperature/humidity sensor.
- USB-C receptacle with CC pull-downs.
- Protected 5 V input path feeding a 3.3 V rail.
- I2C pull-ups, local decoupling, status LED, BOOT and RESET controls.
System Architecture
Diagram
Hardware Subsystems
- Power input: USB-C sink-only input with independent CC1/CC2 5.1k pull-downs.
- Protection: dedicated USB power switch/eFuse style protection preferred for OVP, UVLO, current limiting, and reverse-current blocking.
- Regulation: 5 V to 3.3 V regulator sized for radio peak current with thermal margin.
- Compute/radio: ESP32-C3/S3 class module for 2.4 GHz Wi-Fi plus BLE 5.x.
- Sensor: precision digital humidity/temperature sensor on I2C.
- Debug/firmware: native USB where available, BOOT and RESET controls.
Interfaces and Connections
- USB-C: VBUS, GND, CC1, CC2, D+, D-, shield.
- I2C: SDA, SCL from MCU to sensor, one pull-up pair to 3.3 V.
- GPIO: BOOT, RESET/EN, status LED.
- RF: module antenna at PCB edge with copper keepout during layout.
Power and Runtime Expectations
USB-powered device; low-power firmware should use modem sleep/light sleep between measurements, but USB power removes battery runtime constraints. Current draw must remain within advertised USB-C source capability.
Power Tree and Power Budget
Preliminary load budget:
Table
| Rail | Load | Sleep | Typical active | Peak |
|---|---|---|---|---|
| 3.3 V | Wi-Fi/BLE MCU module | 500 mA continuous draw. |
Physical Design Expectations
- Compact rectangular PCB.
- USB-C connector at board edge.
- MCU antenna at board edge facing outward with no copper/components in antenna keepout.
- Sensor placed away from heat sources such as regulator and MCU; include airflow exposure.
Important Design Decisions
- Use an RF-certified ESP32 module rather than bare RF chip.
- Use a switching regulator instead of small LDO due to Wi-Fi burst current and thermal margin.
- Use a dedicated protected 5 V input/load switch/eFuse for consumer USB robustness.
- Use one I2C pull-up pair for the bus.
Assumptions
- Production-oriented SMD design; no hand-solder requirement stated.
- Indoor consumer environment, non-condensing humidity.
- USB-C is sink-only at 5 V default; no USB Power Delivery negotiation.
- Firmware will keep average current low enough for 0.5 A sources.
Change Notes
- Initial requirements captured from user request.
Project Overview
Intended Use
What the Device Should Do
Main Features
System Architecture
Hardware Subsystems
Interfaces and Connections
Power and Runtime Expectations
Power Tree and Power Budget
Manufacturing and Assembly Expectations
Firmware-Relevant Hardware Requirements
Physical Design Expectations
Important Design Decisions
Assumptions
Change Notes
