Temperature and Humidity Sensor Node Design
Thought for 4 sec
I’ll build the sensor node schematic end-to-end: choose the radio MCU, size the USB-C power path and protection, add the T/RH sensor and support passives, then wire and verify it.
Worked for 3 mins 1 sec
I’ve narrowed the architecture: ESP32-C3 module, SHT41 sensor, protected USB-C input, and a buck regulator to stay cool under Wi-Fi bursts. I’m verifying datasheet details and sizing the power path now.
Worked for 7 mins 54 sec
Architecture is locked and documented. I’m adding the full component set now in functional blocks, then I’ll wire power, USB, MCU support, and the sensor bus.
Worked for 13 mins 25 sec
Done: the USB-C Wi‑Fi/BLE environmental sensor node schematic is built, wired, and ERC-clean. I also added the supporting project files: Project Specification, Design Notes, and Firmware Starter — ESP32-C3-MINI-1-N4.
What’s in place: protected USB-C 5 V input with CC sink resistors, TVS + eFuse protection, 3.3 V buck rail, ESP32-C3 native USB, boot/reset circuitry, and SHT41 on I2C. Schematic is ready for layout; want me to go ahead?
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Project Specification
Summary
Consumer USB-C powered environmental sensor node with Wi-Fi and Bluetooth Low Energy connectivity.
Functional Goals
- Measure ambient temperature and relative humidity with a digital sensor.
- Provide 2.4 GHz Wi-Fi 802.11 b/g/n connectivity.
- Provide Bluetooth LE 5.x connectivity.
- Run from USB-C 5 V sink power only; no USB PD negotiation.
- Support USB 2.0 data for firmware download/debug through the MCU native USB interface.
Selected Architecture
- MCU/Radio module: Espressif ESP32-C3-MINI-1-N4
- Sensor: Sensirion SHT41-AD1B-R2
- USB-C receptacle: GCT USB4215-03-A
- Input protection: TPS25940L eFuse with reverse-current blocking, programmable UVLO, programmable OVP, and programmable OCP
- 3.3 V regulator: MP2122A synchronous buck configured for 3.3 V
Electrical Requirements
- Input source: USB-C receptacle, sink/device role
- Input voltage: 5 V nominal from USB-C source
- Advertised source planning: 0.5 A to 3 A capable sources
- Internal rail: 3.3 V for MCU, sensor, and support circuitry
- Consumer-oriented protection: reverse-current blocking, OVP, UVLO, OCP, USB ESD protection, VBUS TVS
Interfaces
- USB-C CC1/CC2 with 5.1 kOhm Rd pull-downs
- Native USB D+ / D- routed to ESP32-C3 GPIO19 / GPIO18
- I2C from ESP32-C3 to SHT41
- Status LED driven by MCU GPIO
- BOOT and RESET buttons
Power Notes
- Use buck regulation instead of an LDO to avoid excessive dissipation during Wi-Fi TX bursts.
- Keep peak input current below 500 mA worst-case so the node remains compatible with lower-current 5 V sources while still using a connector/power path rated for up to 3 A sources.
Firmware / Bring-up Expectations
- Native USB for flashing and serial console
- Periodic SHT41 measurements over I2C
- BLE advertisement and Wi-Fi reporting supported by the ESP32-C3 platform
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