#Goal

- Design a compact smart humidity sensor PCB powered from a 5 V DC barrel jack that provides Wi‑Fi and Bluetooth using an ESP32 module, reads temperature & humidity over I2C, includes 3.3 V regulation and input protection, programmer access (UART), user interface (LEDs, reset/boot), mounting provisions, and produces a complete schematic and PCB ready for ERC/DRC checks and BOM output.

#Implementation plan

1. Main modules and ICs

1.1. Place an ESP32 module (recommend ESP32-WROOM-32 or ESP32-WROOM-32U for optional external antenna). Ensure VCC, GND, EN (reset), IO0 (boot), UART TX/RX, and I2C-capable pins are exposed.

1.2. Place a digital humidity/temperature sensor: Sensirion SHT31 (e.g., SHT31-DIS) on I2C.

2. Power input and protection

2.1. Add a 5 V DC barrel jack (standard 2.1/5.5 mm) as VIN input.

2.2. Add input protection: a Schottky diode (e.g., SS14) for reverse protection, a slow-blow or PTC resettable fuse (e.g., MF-R series or equivalent) on VIN, and a TVS (e.g., SMBJ5.0) for surge protection.

2.3. Add EMI/cleaning: ferrite bead on VIN and bulk input cap (e.g., 10 µF electrolytic) plus 0.1 µF ceramic.

2.4. Add a synchronous buck regulator to step 5 V → 3.3 V (recommend MP1584EN or equivalent); include required inductor, input/output capacitors and diode or synchronous MOSFET per regulator datasheet.

3. Supporting passive components

3.1. Decoupling: 0.1 µF and 10 µF decoupling on 3.3 V at the ESP32 and sensor VCC pins.

3.2. I2C pull-ups: two 4.7 kΩ resistors from SDA and SCL to 3.3 V.

3.3. LED resistors: two 330 Ω series resistors for power and activity LEDs.

4. IO, programming and UX

4.1. Add a 4-pin programming header or test pads for GND, 3.3 V (or VREF), TX0, RX0 for UART flashing/debugging.

4.2. Add RESET and BOOT (IO0) tactile pushbuttons wired per ESP32 reference to allow programming.

4.3. Add two status LEDs (Power and Network/Activity) connected to available GPIOs with resistors.

4.4. Add mounting holes and mechanical outline for intended enclosure; add keepouts for barrel jack clearance.

5. Schematic wiring and net naming

5.1. Wire barrel jack → input protection (diode, fuse) → VIN of buck regulator. VIN net name: VIN_5V.

5.2. Buck VOUT → create 3V3 net and connect to all 3.3 V pins of ESP32, SHT31 and pull-ups.

5.3. Tie all GND pins to the Flux library "Ground" component (UID: c2e41937-4268-256c-7ae9-cb8cfb60aed3).

5.4. Connect SDA/SCL from SHT31 to chosen ESP32 I2C pins; add 4.7 kΩ pull-ups to 3V3.

5.5. Connect ESP32 TX/RX to programming header and label nets TX0/RX0.

5.6. Label critical nets (VIN_5V, 3V3, GND, SDA, SCL, TX0, RX0, EN, IO0).

6. Footprints, layout preparation and auto-layout

6.1. Ensure each schematic component has an appropriate footprint (barrel jack, ESP32 module footprint, SHT31 SMD footprint, regulator power stage footprint, LEDs, buttons, header, mounting holes).

6.2. Add board outline and mounting hole locations; keep barrel jack area clear.

6.3. Place high‑current and noisy parts (buck regulator, inductor, bulk caps) close together and near VIN edge; place ESP32 and antenna area away from switching regulator if using onboard antenna.

6.4. Start auto-placement and then run Flux AI auto-routing to resolve airwires. Use recommended trace widths for power nets (e.g., 1 mm / 30–40 mil for moderate current) and standard widths (6–10 mil) for signals.

7. Validation, parts and outputs

7.1. Run ERC/DRC; fix critical errors. Resolve common issues: missing grounds, unconnected power pins, wrong footprint pin mapping.

7.2. Produce BOM with MPNs (ESP32-WROOM-32, SHT31-DIS, MP1584EN or chosen regulator, SS14, SMBJ5.0, MF-R PTC, standard passives) and verify distributor availability.

7.3. Generate Gerber, netlist and BOM CSV for fabrication once DRC is clean.

#Success criteria

- Schematic contains ESP32 module, SHT31 sensor, 5 V barrel jack, buck regulator, input protection, required passives, programming header, LEDs, and buttons with proper net connections (no critical unconnected power or ground pins).

- All components have valid footprints on the PCB; board has mounting holes and mechanical outline; auto-placement/autoroute completes with zero critical DRC errors.

- Power path: barrel jack → protection → buck → stable 3.3 V net supplying ESP32 and sensor; recommended decoupling and pull-ups present.

- BOM lists MPNs (e.g., ESP32-WROOM-32, SHT31-DIS, MP1584EN, SS14, SMBJ5.0) and shows availability/pricing.

- Gerber, netlist and BOM CSV are generated and ready for fabrication handoff.