WiFi Water Flow Meter
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Created 5 project docs
Project Specification — WiFi Water Flow Meter
Status: Draft schematic complete / pre-layout. USB-C powered ESP32 WiFi controller for an external 12 V RS485 ultrasonic water-flow sensor i...
Design Notes and Power Budget — WiFi Water Flow Meter
USB-C 5 V input is protected by MP5016 eFuse and monitored by TUSB320 Type-C controller. SYS_5V feeds a TPS62162 3.3 V / 1 A buck regulator ...
Firmware Starter — ESP32-WROOM-32 Water Flow Meter
MCU: ESP32-WROOM-32 Framework: Arduino via PlatformIO
Board Bring-Up Plan — WiFi Water Flow Meter
Current-limited USB-C 5 V supply or bench supply capable of 3 A. Multimeter and oscilloscope.
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Completed the schematic for the WiFi water flow meter: USB-C input protection/current detection, 3.3 V buck, firmware-controlled 12 V boost, ESP32-WROOM-32, RS485 sensor interface, UART programming header, reset/boot, LEDs, and support passives are all wired. Functional ERC/passive/component checks came back clean; remaining broad review warnings are schematic readability/label-placement cleanup items, not functional connectivity errors.
Created project files:
- Project Specification
- Design Notes and Power Budget
- Firmware Starter
- Board Bring-Up Plan
- Regulatory FCC/CE Notes
Open items:
- Confirm the exact ultrasonic sensor current draw and Modbus register map.
- Before PCB layout, clean up schematic visual label/placement warnings.
- For long outdoor/industrial RS485 cables, consider upgrading to a dedicated RS485 surge TVS array.
Suggested next steps:
- Clean up schematic readability.
- Set board size/stackup and place components with ESP32 antenna keepout.
- Route PCB and run DRC/PI checks.
- Update firmware once the sensor datasheet/register map is known.
Clean, constrain and layout
Clean schematic readability
Create layout constraints
Place PCB components
Harden RS485 protection
Check BOM manufacturability
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Ask about this doc
Project Specification — WiFi Water Flow Meter
Project Overview
Status: Draft schematic complete / pre-layout.
USB-C powered ESP32 WiFi controller for an external 12 V RS485 ultrasonic water-flow sensor intended for a 3/4 inch PVC pipe. The board provides protected USB-C 5 V input, a protected 5 V system rail, 3.3 V logic, a firmware-controlled 12 V sensor rail, RS485 communication, programming access, reset/boot controls, and status LEDs.
Intended Use
- Prototype or production-intent controller board for a packaged ultrasonic flow sensor, not raw ultrasonic transducers.
- External sensor is assumed to clamp/mount to 3/4 inch PVC and provide RS485 data, likely Modbus RTU.
- Device reports flow rate and totalized volume over WiFi.
What the Device Should Do
- Accept 5 V USB-C power.
- Detect USB-C source current capability via TUSB320.
- Power ESP32 and logic from a 3.3 V rail.
- Generate 12 V for the external flow sensor under firmware control.
- Communicate with the sensor over half-duplex RS485.
- Provide UART programming/debug access.
- Indicate power, WiFi status, and flow activity.
Main Features
- USB-C 5 V sink input with MP5016 eFuse protection.
- TPS62162 3.3 V / 1 A buck regulator.
- LM27313 5 V to 12 V boost rail based on TI 5 V to 12 V reference circuit.
- ESP32-WROOM-32 WiFi MCU module.
- SP3485 3.3 V RS485 transceiver with termination, weak bias, and ESD clamps.
- 4-position external sensor connector: +12V, GND, RS485_A, RS485_B.
- 6-pin UART programming header plus RESET and BOOT buttons.
System Architecture
Diagram
Hardware Subsystems
Power Input and Protection
- J1 USB4105-GF-A USB-C receptacle.
- U6 TUSB320 configured as UFP sink: PORT to GND, ADDR to GND, EN_N to GND, VBUS_DET via 900 kΩ.
- U1 MP5016 eFuse current limit set near 3 A, MODE tied low for ~5.75 V OVP clamp, DV/DT capacitor for soft start.
3.3 V Logic Rail
- U2 TPS62162 fixed 3.3 V buck regulator.
- L1 2.2 µH inductor, C6 10 µF input, C7 22 µF output.
- 3V3 powers ESP32, TUSB320 I/O, RS485 transceiver, LEDs, and pull-ups.
12 V Sensor Rail
- U3 LM27313 boost converter using 10 µH inductor, Schottky rectifier, 117 kΩ / 13.3 kΩ feedback, and 220 pF feed-forward capacitor.
- BOOST_EN from ESP32 IO25 drives SHDN high to enable; R10 pulldown keeps the rail off during reset.
- Designed around the LM27313 5 V to 12 V / ~250 mA reference circuit.
MCU / WiFi
- U4 ESP32-WROOM-32 module.
- EN has 10 kΩ pull-up and 1 µF RC delay plus reset button.
- GPIO0 has 10 kΩ pull-up plus boot button.
- UART0 is routed to J3 for programming.
RS485 Sensor Interface
- U5 SP3485 at 3.3 V.
- ESP32 UART2: IO17 TX to DI, IO16 RX from RO.
- IO4 controls tied DE and /RE, with pulldown for default receive mode.
- A/B routed to J2 with 120 Ω termination, 10 kΩ weak failsafe bias, and ESD clamps.
Interfaces and Connections
Table
| Interface | Nets / Pins | Notes |
|---|---|---|
| USB-C power | VBUS_RAW, GND, CC1, CC2 | No USB data used; DP/DN/SBU marked NC |
| Programming header J3 | 3V3, GND, ESP_TXD0, ESP_RXD0, ESP_BOOT_GPIO0, ESP_EN | 3.3 V UART only |
| Sensor connector J2 | 12V_SENSOR, GND, RS485_A, RS485_B | For external powered RS485 ultrasonic sensor |
| I2C | IO21 SDA, IO22 SCL | TUSB320 current detector, addr 0x60 |
| Status LEDs | IO26 WiFi, IO27 Flow, 3V3 Power LED | Active-high GPIO LEDs to GND |
Power Tree and Power Budget
Table
| Rail | Load | Typical | Peak / Design |
|---|---|---|---|
| 3V3 | ESP32 WiFi module | 240 mA | 500 mA |
| 3V3 | SP3485 + TUSB320 + LEDs | ~20 mA | ~60 mA |
| 12V_SENSOR | External ultrasonic RS485 sensor | assumed 100 mA | design reference up to ~250 mA |
| SYS_5V input | 3V3 buck reflected + 12V boost reflected | ~0.6 A | ~1.4 A with 12 V at 250 mA |
Important: USB-C without USB PD is always 5 V. Full 15 W operation requires a Type-C source advertising 3 A. Firmware should check TUSB320 current capability before enabling the 12 V boost at full load.
Manufacturing and Assembly Expectations
- SMD passives are used by default.
- Layout must keep the ESP32 antenna at a board edge with copper keepout.
- Switching-regulator loops for U2 and U3 need compact layout and solid ground return.
- RS485 connector should be placed at board edge; termination/bias may be made optional in layout if this board is not always an RS485 bus end.
Firmware-Relevant Hardware Requirements
- Read flow via RS485/Modbus on UART2: RX IO16, TX IO17, DE/RE IO4.
- Control 12 V sensor rail via BOOST_EN on IO25.
- Read Type-C source capability from TUSB320 over I2C at address 0x60.
- Drive WiFi LED on IO26 and flow LED on IO27.
- Use UART0 programming header with BOOT/RESET buttons.
Physical Design Expectations
- Board edge placement required for ESP32 antenna.
- USB-C and sensor terminal should face outward for cable access.
- Add test points in layout for VBUS_RAW, SYS_5V, 3V3, 12V_SENSOR, GND, RS485_A, RS485_B, ESP_EN, and BOOST_EN.
Important Design Decisions
- Used a buck regulator for 3.3 V instead of an LDO to avoid ESP32 WiFi thermal margin issues.
- Added Type-C current detection so firmware can avoid overloading default-current USB-C sources.
- Made 12 V boost firmware-enableable and default-off.
- Used a packaged RS485 ultrasonic sensor assumption; raw ultrasonic transducers would require a different analog front-end design.
Assumptions
- External ultrasonic sensor accepts 12 V and draws <=250 mA peak.
- Sensor protocol is Modbus RTU or similar register-based RS485.
- Product may require a 5 V / 3 A USB-C source for full sensor power.
- RS485 common-mode stress is moderate because this board powers the sensor and shares ground.
Change Notes
- Initial schematic created with power input, regulators, ESP32, RS485 interface, sensor connector, LEDs, programming header, and support passives.
- ERC functional checks currently show no open ERROR/WARNING items for the selected electrical/passive/component review set.
Project Overview
Intended Use
What the Device Should Do
Main Features
System Architecture
Hardware Subsystems
Power Input and Protection
3.3 V Logic Rail
12 V Sensor Rail
MCU / WiFi
RS485 Sensor Interface
Interfaces and Connections
Power Tree and Power Budget
Manufacturing and Assembly Expectations
Firmware-Relevant Hardware Requirements
Physical Design Expectations
Important Design Decisions
Assumptions
Change Notes
