# ESP32 RS485 Water Flow Meter ## Description USB-C powered ESP32 WiFi water flow meter schematic with protected 5V input, 3.3V LDO, 12V boost supply for an external RS485 ultrasonic sensor, UART programming header, boot/reset network, and three status LEDs for power, WiFi, and flow activity. ## Project Details - **Owner:** cochrane - **Created:** 4/25/2026 - **Last Updated:** 4/25/2026 - **Visibility:** Public ## Key Components ### D1 — [SMF5.0A](https://www.flux.ai/lcsc/smf5p0a~bz6b.md) - Package: SOD-123FL - Role Details: TVS clamp from USB VBUS to GND at board power entry - Manufacturer Part Number: SMF5.0A - Role: ESD Protection - Manufacturer Name: Liown(里阳半导体) - Part Type: TVS - Diode Type: Schottky Diode - Forward Voltage: 0.45V to 0.55V (at 1A)V - JLCPCB Part Class: Extended Part - Max Reverse Voltage: 5V - Package or Case Code: SOD-123FL_L2.8-W1.8-LS3.6-RD - LCSC Part Number: C2990427 **Pins:** - 1 [pin 1] - 2 [pin 2] ### D2 — [SS14](https://www.flux.ai/jecstronic/ss14~ri4.md) - Manufacturer Part Number: SS14 - Package: SMA - Datasheet URL: https://datasheet.lcsc.com/lcsc/1912111437_Slkor-SLKORMICRO-Elec--SS14_C444721.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: Slkor(SLKORMICRO Elec.) - Role Details: Schottky rectifier for TPS61040 boost output path - Role: Rectification - Part Type: Diode **Pins:** - Anode [pin A] - Cathode [pin C] ### D3 — [LTST-C190KRKT](https://www.flux.ai/adrian95/ltst-c190krkt~3pw.md) - Role Details: Power LED indicating 3.3V rail presence - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: LTST-C190KRKT - Role: Status Indicator - Part Type: LED - Datasheet URL: https://optoelectronics.liteon.com/upload/download/DS-22-99-0151/LTST-C190KRKT.pdf - Package: 0603 - Manufacturer Name: Lite-On Inc. **Pins:** - A [pin 2] - K [pin 1] ### D4 — [SML-LX0603GW-TR](https://www.flux.ai/adrian95/sml-lx0603gw-tr~uqi.md) - Manufacturer Name: Lumex Opto/Components Inc. - Package: 0603 - Part Type: LED - Datasheet URL: https://www.lumex.com/spec/SML-LX0603GW-TR.pdf - Role Details: WiFi connectivity and activity LED driven by ESP32 GPIO - Role: Status Indicator - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: SML-LX0603GW-TR **Pins:** - A [pin 2] - K [pin 1] ### D5 — [LTST-C190TBKT](https://www.flux.ai/adrian95/ltst-c190tbkt~9us.md) - Manufacturer Name: Lite-On Inc. - Package: 0603 - Datasheet URL: https://optoelectronics.liteon.com/upload/download/DS-22-99-0224/LTST-C190TBKT.PDF - Role Details: Flow activity LED driven by ESP32 GPIO when valid measurement frames are received - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: LED - Manufacturer Part Number: LTST-C190TBKT - Role: Status Indicator **Pins:** - A [pin 2] - K [pin 1] ### J1 — [UJ20-C-H-G-SMT-2-P16-TR](https://www.flux.ai/adrian95/uj20-c-h-g-smt-2-p16-tr~v05.md) - Manufacturer Part Number: UJ20-C-H-G-SMT-2-P16-TR - Package: USB-C receptacle - Mount: Surface Mount - Role Details: USB-C sink-only 5V input connector with CC1 and CC2 configuration pins - Role: Power Input - Datasheet URL: https://www.sameskydevices.com/product/resource/uj20-c-h-g-smt-2-p16-tr.pdf - Manufacturer Name: Same Sky (Formerly CUI Devices) - Part Type: Connector - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - CC1 [pin A5] - CC2 [pin B5] - DN1 [pin A7] - DN2 [pin B7] - DP1 [pin A6] - DP2 [pin B6] - GND [pin A1_B12] - GND__1 [pin B1_A12] - SBU1 [pin A8] - SBU2 [pin B8] - SHIELD [pin SH1] - SHIELD__1 [pin SH2] - SHIELD__2 [pin SH3] - SHIELD__3 [pin SH4] - VBUS [pin A4_B9] - VBUS__1 [pin B4_A9] ### J2 — [640456-6](https://www.flux.ai/adrian95/640456-6~oy5.md) - Role: Programming Header - Package: 1x6 2.54mm - Manufacturer Name: TE Connectivity AMP Connectors - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: UART programming header exposing GND, 3V3, TX0, RX0, DTR, and RTS - Datasheet URL: https://www.te.com/usa-en/product-640456-6.datasheet.pdf - Part Type: Connector - Package or Case Code: SHDR6W66P0X254_1X6_1524X572X1003P - Manufacturer Part Number: 640456-6 **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] - 5 [pin 5] - 6 [pin 6] ### J3 — [61300411121](https://www.flux.ai/adrian95/61300411121~pw9.md) - Role Details: Flow sensor connector carrying GND, +12V, RS485 A, and RS485 B - Role: Sensor Connector - Package: 1x4 2.54mm - Part Type: Connector - Package or Case Code: HDRV4W95P0X254_1X4_1016X254X854P - Manufacturer Name: Wurth Elektronik - Manufacturer Part Number: 61300411121 - Datasheet URL: https://www.we-online.com/components/products/datasheet/61300411121.pdf - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] ### Q1 — [AO3407A](https://www.flux.ai/lcsc/ao3407a~xzrj.md) - Role: Reverse Polarity Protection - LCSC Part Number: C347478 - Role Details: P-channel MOSFET ideal-diode style protection between USB VBUS and protected 5V rail - Package or Case Code: SOT-23_L2.9-W1.3-P1.90-LS2.4-BR - Manufacturer Part Number: AO3407A - JLCPCB Part Class: Extended Part - Transistor Type: N-channel MOSFET - Drain to Source Voltage: 30V - Part Type: MOSFETs - Product Info Url: https://lcsc.com/product-detail/MOSFET_Youtai-Semiconductor-Co-Ltd-AO3407A_C347478.html - Continuous Drain Current: 5A - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2311091734_UMW-Youtai-Semiconductor-Co---Ltd--AO3407A_C347478.pdf - Package: SOT-23 - Manufacturer Name: UMW(友台半导体) **Pins:** - D [pin 3] - G [pin 1] - S [pin 2] ### Q2 — [S8050](https://www.flux.ai/adrian95/s8050~wjp.md) - Part Type: Transistor - Manufacturer Part Number: S8050 - Package: SOT-23 - Role: Auto Reset - Datasheet URL: https://pdf1.alldatasheet.com/datasheet-pdf/view/33773/WINGS/S8050.html - Role Details: NPN transistor pulling GPIO0 low under DTR control for reliable ESP32 bootloader entry - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: MDD **Pins:** - B [pin 1] - C [pin 3] - E [pin 2] ### Q3 — [S8050](https://www.flux.ai/adrian95/s8050~wjp.md) - Role: Auto Reset - Role Details: NPN transistor pulling EN low under RTS control for reliable ESP32 reset sequencing - Manufacturer Name: MDD - License: https://creativecommons.org/licenses/by/4.0/ - Datasheet URL: https://pdf1.alldatasheet.com/datasheet-pdf/view/33773/WINGS/S8050.html - Manufacturer Part Number: S8050 - Package: SOT-23 - Part Type: Transistor **Pins:** - B [pin 1] - C [pin 3] - E [pin 2] ### S1 — [SKRKAEE020](https://www.flux.ai/lcsc/skrkaee020~g9gr.md) - Package: SMD tact switch - Product Info Url: https://lcsc.com/product-detail/Tactile-Switches_ALPS_SKRKAEE020_3-4-2-1-57N_C115357.html - Role: Reset Control - LCSC Part Number: C115357 - Throw Configuration: SPST - Package or Case Code: SW-SMD_L3.9-W3.0-P4.45 - Voltage Rating: 12V - JLCPCB Part Class: Extended Part - Manufacturer Part Number: SKRKAEE020 - Switch Type: Tactile Switch (Momentary) - Part Type: Tactile Switches - Current Rating: 50mA - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/1809201020_ALPSALPINE-SKRKAEE020_C115357.pdf - Manufacturer Name: ALPSALPINE(阿尔卑斯阿尔派) - Role Details: Manual reset pushbutton pulling ESP32 EN low **Pins:** - 1 [pin 1] - 2 [pin 2] ### S2 — [SKRKAEE020](https://www.flux.ai/lcsc/skrkaee020~g9gr.md) - Voltage Rating: 12V - Package or Case Code: SW-SMD_L3.9-W3.0-P4.45 - Throw Configuration: SPST - LCSC Part Number: C115357 - Package: SMD tact switch - Product Info Url: https://lcsc.com/product-detail/Tactile-Switches_ALPS_SKRKAEE020_3-4-2-1-57N_C115357.html - Manufacturer Name: ALPSALPINE(阿尔卑斯阿尔派) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/1809201020_ALPSALPINE-SKRKAEE020_C115357.pdf - Current Rating: 50mA - Part Type: Tactile Switches - Switch Type: Tactile Switch (Momentary) - Manufacturer Part Number: SKRKAEE020 - JLCPCB Part Class: Extended Part - Role: Boot Control - Role Details: Manual bootloader entry button pulling ESP32 GPIO0 low **Pins:** - 1 [pin 1] - 2 [pin 2] ### U1 — [ESP32-WROOM-32D](https://www.flux.ai/vasy_skral/esp32-wroom-32d~o5t.md) - Role: WiFi MCU - Symbol Style: parametric-v1 - Datasheet URL: https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32d_esp32-wroom-32u_datasheet_en.pdf - Manufacturer Name: Espressif Systems - Role Details: Main ESP32 module handling RS485 sensor polling, flow calculations, and WiFi reporting - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Module - Package: Module - Manufacturer Part Number: ESP32-WROOM-32D **Pins:** - 3V3 [pin 2] - EN [pin 3] - GND [pin 39_16] - GND [pin 39_14] - GND [pin 1] - GND [pin 39_17] - GND [pin 15] - GND [pin 39_12] - GND [pin 39_11] - GND [pin 39_5] - GND [pin 39_3] - GND [pin 39_13] - GND [pin 39_21] - GND [pin 38] - GND [pin 39_10] - GND [pin 39_19] - GND [pin 39_1] - GND [pin 39_6] - GND [pin 39_9] - GND [pin 39_18] - GND [pin 39_20] - GND [pin 39_7] - GND [pin 39_8] - GND [pin 39_4] - GND [pin 39_15] - GND [pin 39_2] - IO0 [pin 25] - IO12 [pin 14] - IO13 [pin 16] - IO14 [pin 13] - IO15 [pin 23] - IO16 [pin 27] - IO17 [pin 28] - IO18 [pin 30] - IO19 [pin 31] - IO2 [pin 24] - IO21 [pin 33] - IO22 [pin 36] - IO23 [pin 37] - IO25 [pin 10] - IO26 [pin 11] - IO27 [pin 12] - IO32 [pin 8] - IO33 [pin 9] - IO34 [pin 6] - IO35 [pin 7] - IO4 [pin 26] - IO5 [pin 29] - RXD0 [pin 34] - SCK/CLK [pin 20] - SCS/CMD [pin 19] - SDI/SD1 [pin 22] - SDO/SD0 [pin 21] - SENSOR_VN [pin 5] - SENSOR_VP [pin 4] - SHD/SD2 [pin 17] - SWP/SD3 [pin 18] - TXD0 [pin 35] ### U2 — [ME6211C33M5G-N](https://www.flux.ai/jecstronic/me6211c33m5g-n~a2.md) - Role: Voltage Regulation - Manufacturer Name: MICRONE(Nanjing Micro One Elec) - Part Type: LDO - Datasheet URL: https://datasheet.lcsc.com/lcsc/1811131510_MICRONE-Nanjing-Micro-One-Elec-ME6211C33M5G-N_C82942.pdf - Role Details: 3.3V LDO regulator from protected 5V rail for ESP32 and RS485 transceiver - Manufacturer Part Number: ME6211C33M5G-N - Package: SOT-23-5 **Pins:** - CE - NC - VIN - VOUT - VSS ### U3 — [Boost Converter](https://www.flux.ai/corynrobinson/boost-converter~kq.md) - Part Type: Integrated Circuit - Manufacturer Part Number: TPS61040DBVR - Role Details: Boost converter generating 12V rail from protected 5V for external ultrasonic flow sensor - Purchase Url: https://octopart.com/tps61040dbvr-texas+instruments-439784?r=sp - Manufacturer Name: Texas Instruments - Product Info Url: https://www.ti.com/product/TPS61040#cad-cae-symbols - Datasheet URL: https://www.ti.com/lit/ds/symlink/tps61040.pdf?ts=1648612135061&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS61040 - Package or Case Code: SOT-23 - Package: SOT-23-5 - Role: Voltage Boost **Pins:** - EN - FB - GND - SW - VIN ### U4 — [MAX3485ESA+](https://www.flux.ai/lcsc/max3485esaplus~baoy.md) - Manufacturer Name: MAXIM(美信) - LCSC Part Number: C1545222 - Role: RS485 Interface - Manufacturer Part Number: MAX3485ESA+ - Package: SOIC-8 - Role Details: Half-duplex RS485 transceiver with DI, RO, DE, and RE for ESP32 UART sensor communications - JLCPCB Part Class: Extended Part - Package or Case Code: SO-8_L4.9-W3.9-P1.27-LS6.0-BL **Pins:** - ~{RE} [pin 2] - A [pin 6] - B [pin 7] - DE [pin 3] - DI [pin 4] - GND [pin 5] - RO [pin 1] - VCC [pin 8] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/cochrane/esp32-rs485-water-flow-meter~w7](https://www.flux.ai/cochrane/esp32-rs485-water-flow-meter~w7).* --- *Generated from [https://www.flux.ai/cochrane/esp32-rs485-water-flow-meter~w7](https://www.flux.ai/cochrane/esp32-rs485-water-flow-meter~w7)*