WiFi Water Flow Meter Design
0:03
Work done
- Set the layout to 80 mm x 60 mm with a Standard 4 Layer stackup and compacted the board from the previously oversized outline. This matches the stage-2 and layout guidance to explicitly set board size and stackup before placement, and to use a 4-layer board for an ESP32 design with USB and multiple rails
- Grouped the placement by functional block:
- Placed U1 at the top-right board edge with the antenna side facing outward and using an antenna overhang rule consistent with the ESP32 placement guidance for PCB antennas at the board edge
- Verified the placement pass completed cleanly with no overlap or out-of-bounds placement problems. The only remaining review items are unrouted electrical connections, which are expected because trace routing has not been done yet.
Success criteria review
- ✅ The board size is set to 80 mm x 60 mm and the layout still has comfortable routing space
- ✅ Components are grouped into clear power, MCU/communication, RS485, and sensor/interface regions
- ✅ The ESP32 antenna on U1 is positioned at the board edge for RF-friendly placement
Review RF clearances
Set routing rules
Optimize critical placement
12 days
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Project Specification
Summary
WiFi-enabled water flow meter for a 3/4 inch PVC pipe using an external 12 V ultrasonic flow sensor with RS485 communications. The board is powered from USB-C 5 V input, generates regulated 3.3 V for control electronics and 12 V for the sensor, and reports flow rate and totalized volume through an ESP32 WiFi module.
Architecture
Diagram
Functional Blocks
- USB-C sink power input with CC pull-down resistors, VBUS ESD protection, reverse-current and reverse-polarity style ideal-diode MOSFET stage, and bulk plus local decoupling.
- 3.3 V low-noise regulation for ESP32, RS485 transceiver, and logic.
- 5 V to 12 V boost converter to power the external ultrasonic sensor.
- ESP32-WROOM-32D WiFi controller with UART programming header, BOOT and RESET support, EN filtering, and dedicated status LEDs.
- Half-duplex RS485 interface to an external ultrasonic flow sensor connector carrying GND, +12 V, RS485 A, and RS485 B.
- Flow rate and total volume calculations performed in ESP32 firmware from RS485 sensor data.
Planned Interfaces
USB-C Power Input
- USB-C receptacle used as a 5 V sink only.
- CC1 and CC2 each use 5.1k pull-down resistors to GND.
- Protected 5 V rail feeds both the 3.3 V regulator and 12 V boost converter.
Programming Header
- UART header exposes GND, 3.3 V reference, ESP32 TX0, ESP32 RX0, DTR, and RTS.
- DTR and RTS support automatic BOOT and RESET sequencing through the ESP32 reset network.
Flow Sensor Connector
- Pin 1: GND
- Pin 2: +12 V sensor power
- Pin 3: RS485 A
- Pin 4: RS485 B
Design Decisions
- Use an ESP32 module rather than a bare chip to avoid RF matching and antenna design risk.
- Use a 3.3 V LDO because the 5 V to 3.3 V rail drop is moderate and the circuit benefits from simplicity and low noise.
- Use a dedicated boost converter because the external ultrasonic sensor requires 12 V while the system input is USB-C 5 V.
- Perform flow-rate and total-volume calculations in firmware because the ultrasonic sensor already communicates digitally over RS485.
Validation Goals
- All power rails are protected, decoupled, and connected to their intended loads.
- ESP32 boot and reset behavior is deterministic and suitable for UART programming.
- RS485 interface includes correct bus connections and support components for reliable single-sensor communication.
- The schematic is complete enough to proceed to PCB layout after ERC review.
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