WiFi BLE Sensor Node Design
Worked for 1 min 27 sec
I started the design and renamed the project to Industrial WiFi BLE T-RH Node with a matching description and project properties. I also created a Design Notes project file capturing requirements, architecture, and preliminary power budget.
Added schematic parts so far:
- USB-C 2.0 receptacle
- TPS2595-series eFuse/input protection
- AP2112K-3.3 LDO
- ESP32-C3-MINI-1-N4 WiFi/BLE module
- SHT40 digital temperature/humidity sensor
- USBLC6-2SC6 USB data ESD protection
- BOOT and RESET tactile switches
I consulted datasheets for the ESP32-C3, SHT40, and AP2112. The passive support components were not added yet because the generic passive add attempt failed right before execution stopped; I found the correct generic resistor/capacitor library IDs afterward, but could not continue due to credits running out.
Remaining work:
- Add support passives: USB-C CC 5.1 kΩ pull-downs, eFuse setting parts, LDO input/output caps, 3.3 V bulk cap, ESP32 EN/BOOT passives, I2C pull-ups, and sensor decoupling.
- Wire all nets: USB VBUS, protected 5 V, 3.3 V, GND, USB D+/D-, EN, BOOT, I2C SDA/SCL.
- Mark unused ESP32/connector pins no-connect where appropriate.
- Re-run schematic review/ERC and fix violations.
- Create firmware starter and board bring-up plan files.
- After schematic passes review, ask for approval before moving to PCB layout.
Add support passives
Wire main nets
Run ERC check
Firmware starter plan
Document design choices
Refine this doc
Ask about this doc
Design Notes
Requirements
- Industrial temperature and relative humidity sensor node.
- USB-C 5 V default sink input, expected source capability range 0.5 A to 3 A.
- Include reverse-current/reverse-polarity protection, over-voltage protection, under-voltage lockout, and over-current protection.
- Low-power MCU with dual radio: 2.4 GHz 802.11 b/g/n WiFi and BLE 5.x.
- Digital temperature/RH sensor.
Architecture
USB-C receptacle provides 5 V VBUS through input protection to a 3.3 V regulator. The 3.3 V rail powers an ESP32-C3/S3-class WiFi/BLE module and an I2C temperature/RH sensor. USB D+/D- are routed to the MCU native USB interface if the selected MCU module supports it; otherwise they are reserved/no-connect.
Preliminary Power Budget
Estimated loads on 3.3 V rail:
- WiFi/BLE MCU module: ~80 mA active typical, up to ~400–500 mA short WiFi TX peaks depending on module and RF conditions.
- Digital T/RH sensor: <1 mA active, microamp sleep.
- Pull-ups/status LED/support: <5–10 mA depending firmware.
Design target: size 3.3 V regulator for at least 600 mA peak. Input protection path should tolerate at least 1 A continuous with margin and not prevent operation from 0.5 A USB sources when firmware limits transmit/load duty cycle. For 3 A advertised USB-C sources, the design will remain a low-power sink rather than consuming the full 3 A unless future expansion loads are added.
Initial Part Direction
- MCU: ESP32-C3 or ESP32-S3 module for integrated antenna/certified RF and BLE 5.x + 802.11 b/g/n.
- Sensor: Sensirion SHT4x/SHT3x industrial-grade digital I2C T/RH sensor.
- Power input protection: USB-C CC pull-downs, VBUS ESD/TVS, eFuse/load switch with OVP/UVLO/OCP/reverse-current blocking, then 3.3 V regulator with datasheet-required capacitors.
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