# Agricultural RS-485 Sensor Node ## Description Compact 45 mm x 35 mm 4-layer agricultural IoT sensor node using an ATmega4808, AMS1117-3.3 linear regulation from 12 V input, RS-485 Modbus RTU half-duplex, local I2C sensors, 0.96 inch OLED, status LED, and a 12 V solenoid valve driver with top-side sensors/display and bottom-side MCU/power partitioning. ## Project Details - **Owner:** tbhvision - **Created:** 4/13/2026 - **Last Updated:** 6/5/2026 - **Visibility:** Public - **Implementation Details:** Frozen device map update: U3 is strictly MAX485CSA+ in SOIC-8. Generic MAX485-class and alternate RS-485 transceiver variants are excluded from this project. ## Key Components ### D1 — [SS14LW RVG](https://www.flux.ai/lcsc/ss14lw-rvg~p3ge.md) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2304140030_Taiwan-Semiconductor-SS14LW-RVG_C484050.pdf - Role: Flyback diode - Part Type: Schottky Barrier Diodes (SBD) - Product Info Url: https://lcsc.com/product-detail/New-Arrivals_Taiwan-Semiconductor-Taiwan-Semicon-SS14LW-RVG_C484050.html - LCSC Part Number: C484050 - JLCPCB Part Class: Extended Part - Manufacturer Name: Taiwan Semiconductor(台湾半导体) - Package or Case Code: SOD-123W_L2.8-W1.8-LS3.7-RD - Role Details: Suppresses inductive kick from 12V solenoid - Manufacturer Part Number: SS14LW RVG - Package: DO-214AC **Pins:** - A [pin 2] - K [pin 1] ### D2 — [SS14LW RVG](https://www.flux.ai/lcsc/ss14lw-rvg~p3ge.md) - Package: DO-214AC - JLCPCB Part Class: Extended Part - LCSC Part Number: C484050 - Manufacturer Name: Taiwan Semiconductor(台湾半导体) - Package or Case Code: SOD-123W_L2.8-W1.8-LS3.7-RD - Manufacturer Part Number: SS14LW RVG - Role Details: Protects Q2 from fan inductive kick - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2304140030_Taiwan-Semiconductor-SS14LW-RVG_C484050.pdf - Part Type: Schottky Barrier Diodes (SBD) - Role: Flyback diode - Product Info Url: https://lcsc.com/product-detail/New-Arrivals_Taiwan-Semiconductor-Taiwan-Semicon-SS14LW-RVG_C484050.html **Pins:** - A [pin 2] - K [pin 1] ### IC1 — [HDC1080DMBR](https://www.flux.ai/adrian95/hdc1080dmbr~9zq.md) - Role: Temperature and humidity sensor - Role Details: HDC1080 I2C sensor, NC pins floating and DAP left floating - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: HDC1080DMBR - Part Type: Sensor - Package or Case Code: SON100P300X300X80-7N - Manufacturer Name: Texas Instruments - Package: WSON DMB 6-pin 3x3mm - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fhdc1080 **Pins:** - EXP [pin 7] - GND [pin 2] - NC_3 [pin 3] - NC_4 [pin 4] - SCL [pin 6] - SDA [pin 1] - VDD [pin 5] ### J1 — [SM04B-SRSS-TB(LF)(SN)](https://www.flux.ai/lcsc/sm04b-srss-tblfsn~a667.md) - Package: CONN-SMD_4P-P1.00 - Product Info Url: https://lcsc.com/product-detail/Others_JST-Sales-America__JST-Sales-America-SM04B-SRSS-TB-LF-SN_C160404.html - Role: Bus input connector - Package or Case Code: CONN-SMD_4P-P1.00_SM04B-SRSS-TB-LF-SN - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2304140030_JST-SM04B-SRSS-TB-LF-SN_C160404.pdf - Manufacturer Part Number: SM04B-SRSS-TB(LF)(SN) - Manufacturer Name: JST - LCSC Part Number: C160404 - Part Type: Wire To Board / Wire To Wire Connector - JLCPCB Part Class: Extended Part - Role Details: Pins 1-4 map to VIN_12V, GND, RS485_A, RS485_B **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] - 5 [pin 5] - 6 [pin 6] ### J2 — [SM04B-SRSS-TB(LF)(SN)](https://www.flux.ai/lcsc/sm04b-srss-tblfsn~a667.md) - JLCPCB Part Class: Extended Part - Role Details: Pins 1-4 map to VIN_12V, GND, RS485_A, RS485_B - Manufacturer Name: JST - LCSC Part Number: C160404 - Part Type: Wire To Board / Wire To Wire Connector - Product Info Url: https://lcsc.com/product-detail/Others_JST-Sales-America__JST-Sales-America-SM04B-SRSS-TB-LF-SN_C160404.html - Manufacturer Part Number: SM04B-SRSS-TB(LF)(SN) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2304140030_JST-SM04B-SRSS-TB-LF-SN_C160404.pdf - Package or Case Code: CONN-SMD_4P-P1.00_SM04B-SRSS-TB-LF-SN - Package: CONN-SMD_4P-P1.00 - Role: Bus output connector **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] - 5 [pin 5] - 6 [pin 6] ### J3 — [S3B-PH-SM4-TB(LF)(SN)](https://www.flux.ai/adrian95/s3b-ph-sm4-tblfsn~q3c.md) - Manufacturer Part Number: S3B-PH-SM4-TB(LF)(SN) - Datasheet URL: https://www.jst-mfg.com/product/pdf/eng/ePH.pdf - Role: Soil moisture connector - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: JST Sales America Inc. - Role Details: Pin 1 3V3, pin 2 GND, pin 3 SOIL_MOISTURE_ADC - Package: JST-PH 2.0mm 3-pin SMD - Part Type: Connector **Pins:** - Pin_1 [pin 1] - Pin_2 [pin 2] - Pin_3 [pin 3] ### J4 — [KF301-2P](https://www.flux.ai/adrian95/kf301-2p~rhx.md) - Role: Solenoid connector - Part Type: Connector - Manufacturer Name: Handson Technology - Role Details: Pin 1 VALVE_LOW, pin 2 VIN_12V - Datasheet URL: https://www.handsontec.com/dataspecs/terminal%20block-5mm.pdf - Package: KF301-2P - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: KF301-2P - Package or Case Code: HANDSON_KF301-2P **Pins:** - 1 [pin 1] - 2 [pin 2] ### J5 — [22-28-4033](https://www.flux.ai/adrian95/22-28-4033~4k2.md) - Connector Positions: 3 - Connector Pitch: 2.54mm - Connector Rows: 1 - Connector Gender: Male - Connector Type: Headers and Wire Housings - Role Details: Pin 1 GND, pin 2 UPDI, pin 3 3V3 - Manufacturer Name: Molex - Role: Programming header - Manufacturer Part Number: 0022284033 - Part Type: Connector - Datasheet URL: https://www.molex.com/pdm_docs/sd/022284033_sd.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Package: 2.54mm 3-pin THT **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### J6 — [B2B-XH-A(LF)(SN)](https://www.flux.ai/lcsc/b2b-xh-alfsn~xrt.md) - Part Type: Wire To Board / Wire To Wire Connector - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2304140030_JST-B2B-XH-A-LF-SN_C158012.pdf - Rows: 1 - Pitch: 2.5mm - Manufacturer Name: JST - Role: Fan connector - Manufacturer Part Number: B2B-XH-A(LF)(SN) - Gender: Male - Product Info Url: https://lcsc.com/product-detail/XH-Connectors_JST_B2B-XH-A-LF-SN_XHsocket-1-2P-pitch2-5mm_C158012.html - LCSC Part Number: C158012 - Positions: 2 - Package or Case Code: CONN-TH_B2B-XH-A-LF-SN - JLCPCB Part Class: Extended Part - Role Details: Pin 1 = FAN_12V, Pin 2 = GND - Connector Type: Wire To Board / Wire To Wire Connector **Pins:** - 1 [pin 1] - 2 [pin 2] ### LED1 — [MHPA1010RGBDT](https://www.flux.ai/lcsc/mhpa1010rgbdt~5tf8.md) - JLCPCB Part Class: Extended Part - Package: 1010 - LCSC Part Number: C404280 - Manufacturer Name: MEIHUA(美华) - Manufacturer Part Number: MHPA1010RGBDT - Role Details: Common-anode RGB indicator driven active-low from ATmega4808 PD4/PD5/PD6 - Role: Status LED - Product Info Url: https://lcsc.com/product-detail/Light-Emitting-Diodes-LED_MEIHUA-MHPA1010RGBDT_C404280.html - Part Type: Light Emitting Diodes (LED) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2409272202_MEIHUA-MHPA1010RGBDT_C404280.pdf - Package or Case Code: LED-ARRAY-SMD_4P-L1.0-W1.0-TR-RD **Pins:** - + [pin 1] - B- [pin 4] - G- [pin 3] - R- [pin 2] ### OLED1 — [OLED 128 x 64 0.96inch](https://www.flux.ai/lmiller/oled-128-x-64-0p96inch~gt.md) - Role Details: 0.96 inch I2C OLED for local status and readings - Role: Display - Package: Module - Part Type: Display Device **Pins:** - 5V [pin 2] - GND [pin 1] - SCL [pin 3] - SDA [pin 4] ### Q1 — [AO3400](https://www.flux.ai/lcsc/ao3400~y44d.md) - Manufacturer Name: YFW(佑风微) - Package: SOT-23 - Transistor Type: N-channel MOSFET - LCSC Part Number: C2977509 - Manufacturer Part Number: AO3400 - Part Type: MOSFETs - Role Details: 3.3V-driven low-side switch for 12V solenoid valve - Role: Valve driver MOSFET - Package or Case Code: SOT-23-3_L3.0-W1.7-P0.95-LS2.9-BR - JLCPCB Part Class: Extended Part - Continuous Drain Current: 5A (Maximum) at 25°C - Drain to Source Voltage: 30V **Pins:** - D [pin 3] - G [pin 1] - S [pin 2] ### Q2 — [AO3400](https://www.flux.ai/lcsc/ao3400~y44d.md) - Part Type: MOSFETs - Role: Fan driver MOSFET - Drain to Source Voltage: 30V - Package or Case Code: SOT-23-3_L3.0-W1.7-P0.95-LS2.9-BR - Manufacturer Name: YFW(佑风微) - JLCPCB Part Class: Extended Part - Transistor Type: N-channel MOSFET - LCSC Part Number: C2977509 - Continuous Drain Current: 5A (Maximum) at 25°C - Manufacturer Part Number: AO3400 - Role Details: 3.3V-driven low-side switch for 12V fan **Pins:** - D [pin 3] - G [pin 1] - S [pin 2] ### U1 — [ATMEGA4808-AFR](https://www.flux.ai/adrian95/atmega4808-afr~ebv.md) - Manufacturer Name: Microchip - Package: TQFP-32 - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Microcontroller - Role Details: ATmega4808 3.3V controller for sensors, OLED, RS-485, and solenoid control - Manufacturer Part Number: ATMEGA4808-AFR - Datasheet URL: https://ww1.microchip.com/downloads/en/DeviceDoc/ATmega4808-09-DataSheet-DS40002173C.pdf - Role: Main MCU **Pins:** - AVDD [pin 18] - EXTCLK/PA0 [pin 30] - GND [pin 19] - GND [pin 29] - PA1 [pin 31] - PA2 [pin 32] - PA3 [pin 1] - PA4 [pin 2] - PA5 [pin 3] - PA6 [pin 4] - PA7 [pin 5] - PC0 [pin 6] - PC1 [pin 7] - PC2 [pin 8] - PC3 [pin 9] - PD0 [pin 10] - PD1 [pin 11] - PD2 [pin 12] - PD3 [pin 13] - PD4 [pin 14] - PD5 [pin 15] - PD6 [pin 16] - PD7 [pin 17] - PF0/TOSC1 [pin 20] - PF1/TOSC2 [pin 21] - PF2 [pin 22] - PF3 [pin 23] - PF4 [pin 24] - PF5 [pin 25] - PF6/~RESET [pin 26] - UPDI [pin 27] - VDD [pin 28] ### U2 — [AMS1117-3.3RG](https://www.flux.ai/lcsc/ams1117-3p3rg~47um.md) - Manufacturer Name: HGC(深圳汉芯) - LCSC Part Number: C2977152 - Package: SOT-223 - Manufacturer Part Number: AMS1117-3.3RG - Package or Case Code: SOT-223-3_L6.4-W3.5-P2.30-LS7.0-BR - Part Type: Linear Voltage Regulators (LDO) - Role Details: Use AMS1117-3.3 linear regulator only; no switching regulator or inductor - JLCPCB Part Class: Extended Part - Role: 3.3V linear regulator **Pins:** - ADJ/GND [pin 1] - IN [pin 3] - OUT [pin 2] - OUT [pin 4] ### U3 — [MAX485CSA+](https://www.flux.ai/lcsc/max485csaplus~l32h.md) - Part Type: RS-485/RS-422 ICs - Product Info Url: https://lcsc.com/product-detail/RS-485-RS-422_MAXIM_MAX485CSA_MAX485CSA_C143494.html - Role Details: Frozen exact device identity for half-duplex Modbus RTU interface: MAX485CSA+ only - LCSC Part Number: C143494 - Manufacturer Part Number: MAX485CSA+ - JLCPCB Part Class: Extended Part - Datasheet URL: https://assets.lcsc.com/datasheet/szlcsc/Download-ISO9001-Certification.pdf - Manufacturer Name: ADI(亚德诺)/MAXIM(美信) - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Role: RS-485 transceiver - Package: SOIC-8 **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] ### U4 — [BH1750FVI-TR](https://www.flux.ai/jecstronic/bh1750fvi-tr~3qz.md) - Role: Ambient light sensor - Manufacturer Part Number: BH1750FVI-TR - Datasheet URL: https://datasheet.lcsc.com/lcsc/1811081611_ROHM-Semicon-BH1750FVI-TR_C78960.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Sensor - Package: WSOF6I - Role Details: BH1750 I2C light sensor, address 0x23 with ADDR tied low - Manufacturer Name: Rohm Semiconductor **Pins:** - ADDR [pin 2] - DVI [pin 5] - EP [pin 7] - GND [pin 3] - SCL [pin 6] - SDA [pin 4] - VCC [pin 1] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/tbhvision/agricultural-rs-485-sensor-node~ki](https://www.flux.ai/tbhvision/agricultural-rs-485-sensor-node~ki).* --- *Generated from [https://www.flux.ai/tbhvision/agricultural-rs-485-sensor-node~ki](https://www.flux.ai/tbhvision/agricultural-rs-485-sensor-node~ki)*