Temperature and Humidity Sensor Node Design
Thought for 3 sec
Work done
- Built the USB-C powered ESP32-C3 temperature/RH sensor node schematic with USB-C CC pull-downs, TPS259530 protection, TLV75533 3.3 V regulation, SHTC3 I2C sensor, decoupling, reset/boot circuitry, UART header, and GPIO2 boot strap pull-up.
- Cleaned ERC warnings by wiring R10 and marking unused ESP32-C3 GPIOs intentional no-connects.
- Set the PCB to a 50 mm × 50 mm rounded 4-layer board and placed all components with USB-C at the edge, ESP32 antenna at the top edge, sensor away from heat, and header accessible on the right.
- Updated Design Notes and created Firmware Starter — ESP32-C3-MINI-1-N4.
- ✅ Required schematic components and power protection are present.
- ✅ Electrical support parts are included: CC resistors, I2C pull-ups, 100 nF decoupling, EN RC reset, BOOT controls, and programming header.
- ✅ ERC is clean for the checked schematic issues; footprints, invalid layers, and overlapping copper checks pass.
- ✅ Preliminary PCB layout planning is complete with board outline, stackup, and RF-aware placement.
- ⚠️ Routing is not complete yet: the board still has 43 airwire reports because traces have not been routed.
- Route the PCB next, then re-run DRC/airwire checks and prepare manufacturing exports if desired.
Route remaining airwires
Full design review
Prepare manufacturing exports
Verify antenna keepout
Refine this doc
Ask about this doc
Design Notes
Objective
Low-power consumer temperature and humidity sensor node powered from USB-C 5 V default current, using an ESP32-C3 Wi-Fi/BLE module and Sensirion SHTC3 I2C temperature/RH sensor.
Architecture
- USB-C receptacle J1 provides 5 V VBUS.
- CC1/CC2 each use 5.1 kΩ pull-down resistors for USB-C sink/UFP default-power advertisement.
- VBUS is clamped by D1 TVS and filtered by C1/C2.
- TPS259530 eFuse U1 protects the input path and provides reverse-current blocking, OVP/UVLO/OCP behavior, thermal shutdown, and controlled startup.
- TLV75533 LDO U2 regulates protected 5 V to 3.3 V.
- ESP32-C3-MINI-1-N4 U3 provides 2.4 GHz Wi-Fi and BLE 5.x.
- SHTC3 U4 provides I2C temperature and humidity sensing.
Power/protection assumptions
- USB-C PD negotiation is not implemented; this is a default 5 V sink.
- OCP target is approximately 3 A using R9 = 665 Ω on TPS259530 ILM.
- UVLO follows the TPS2595xx datasheet example for about 4.3 V using R7 = 1 MΩ and R8 = 387 kΩ.
- dVdt soft-start capacitor C8 = 3.3 nF.
- LDO input/output capacitors use 1 µF ceramic; local 100 nF decoupling is included at MCU and sensor rails.
Digital interfaces
- I2C bus: ESP32 IO4 = SDA, IO5 = SCL, both pulled up to 3.3 V with 4.7 kΩ.
- UART/debug header J2: 3V3, GND, TXD0, RXD0, EN, BOOT.
- EN has 10 kΩ pull-up plus 1 µF RC delay capacitor and reset button.
- BOOT uses GPIO9 with 10 kΩ pull-up and button to GND for download mode.
PCB planning
- Consumer IoT sensor node; selected preliminary board is compact rectangular 50 mm × 50 mm with Standard 4 Layer stackup for solid RF/power return paths.
- USB-C connector should sit on a board edge.
- ESP32 module antenna must face outward at the board edge with antenna keepout respected.
- Keep SHTC3 away from the LDO/eFuse heat sources and away from direct USB connector thermal mass when possible.
Welcome 👋
Flux helps you build PCBs faster with an AI teammate!
Create your account to collaborate, stay updated, fork your own version, and get instant answers from our AI agent.