WiFi Water Flow Meter
Worked for 10 mins 1 sec
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
Design Notes and Power Budget — WiFi Water Flow Meter
Architecture Summary
- 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 and an LM27313 12 V boost converter.
- ESP32 controls the 12 V boost enable, reads Type-C current capability over I2C, and communicates with the sensor over RS485.
USB-C Current Limit Assumption
USB-C without PD only guarantees 5 V. Available current depends on Type-C Rp advertisement:
Table
| Source Mode | Available Power |
|---|---|
| Default USB current | ~2.5 W to 4.5 W class depending source |
| Type-C 1.5 A | 7.5 W |
| Type-C 3.0 A | 15 W |
The schematic includes TUSB320 so firmware can determine whether the source advertises default, 1.5 A, or 3 A. Full 12 V sensor operation should require 3 A advertisement unless the actual sensor current is proven lower.
Estimated Power Budget
Table
| Rail | Load | Typical | Peak / Design |
|---|---|---|---|
| 3V3 | ESP32 WiFi | 240 mA | 500 mA |
| 3V3 | SP3485 RS485 | 2 mA | 60 mA transient/loaded TX allowance |
| 3V3 | TUSB320 + pull-ups | <2 mA | <5 mA |
| 3V3 | 2 GPIO LEDs | 2 to 4 mA each with 1 kΩ | ~6 mA total |
| 12V_SENSOR | External ultrasonic sensor | assumed 100 mA | design reference 250 mA |
Input Current Reflection
Assuming 85% boost efficiency and 90% buck efficiency:
Table
| Load Case | Input Current at 5 V |
|---|---|
| 3V3 rail, 560 mA peak | (3.3 V × 0.56 A)/(5 V × 0.90) = 0.41 A |
| 12 V rail, 100 mA | (12 V × 0.10 A)/(5 V × 0.85) = 0.28 A |
| 12 V rail, 250 mA | (12 V × 0.25 A)/(5 V × 0.85) = 0.71 A |
| Peak design total with 250 mA sensor | ~1.12 A plus inrush margin |
The MP5016 current limit is set near 3 A for compatibility with a 5 V / 3 A Type-C source, but firmware should still derate behavior when the source advertises less current.
Regulator Choices
TPS62162 3.3 V Buck
- Fixed 3.3 V / 1 A regulator.
- Datasheet support: 2.2 µH inductor, 10 µF input, 22 µF output, PG pull-up.
- Selected over LDO to reduce heat during ESP32 WiFi peaks.
LM27313 12 V Boost
- Reference design: VIN 5 V, VOUT 12 V, IOUT ~250 mA.
- Uses 10 µH inductor, Schottky diode, 117 kΩ / 13.3 kΩ feedback, 220 pF feed-forward capacitor.
- BOOST_EN defaults low using R10; ESP32 drives high to enable 12 V.
Key Risks / Open Items
- Confirm exact external ultrasonic sensor current, startup current, and protocol/register map.
- Replace simple per-line RS485 ESD clamps with a dedicated RS485 surge/TVS array if cable length or industrial surge exposure is significant.
- During layout, keep boost and buck switching loops compact and away from ESP32 antenna.
- Make 120 Ω termination optional if this board might not be one end of the RS485 bus.
Architecture Summary
USB-C Current Limit Assumption
Estimated Power Budget
Input Current Reflection
Regulator Choices
TPS62162 3.3 V Buck
LM27313 12 V Boost
Key Risks / Open Items
