Temperature and Humidity Sensor Node Design
0:03
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
2 days
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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.
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