PICO 1 / 2 PCB LAN RJ454 W5500 DEVELOP BOARD NEXTION 7 inch

PICO 1 / 2 PCB LAN RJ454 W5500 DEVELOP BOARD NEXTION 7 inch

GENERAL OVERVIEW
This board is a multifunction industrial control platform centered around Raspberry Pi Pico (RP2040), combining Ethernet (W5500), dual full-duplex RS-485 channels, thermocouple measurement, motor control (H-bridge), multiple GPIO expansions, and a switching power supply system. It is designed for automation, industrial control, and possibly oven/heating systems (based on thermocouple + motor + power stage).

POWER INPUT AND DISTRIBUTION
The board accepts +12V / +24V motor power input. This input is routed through protection diodes (1N4007 / 1N5404 types) to prevent reverse polarity.

There are two main power conversion paths:

• Linear regulators (7805) for logic and Pico supply

• Switching regulator (LM2596 adjustable) for efficient step-down

Power rails generated:

• +5V (main logic, Pico VBUS, W5500, RS-485)

• +3.3V (Ethernet chip and logic derived from 5V rail)

Large electrolytic capacitors (220uF, 470uF) provide bulk filtering.
100nF capacitors are used for local decoupling across all ICs.

There is separation between motor power and logic power, but grounds are shared.

PICO MICROCONTROLLER CORE
Main controller is Raspberry Pi Pico (RP2040).

Used interfaces:

• SPI for W5500 Ethernet (GPIO16–19 typical mapping)

• UART1 and UART2 for RS-485 communication

• GPIO lines expanded to multiple headers

• ADC pins available but not heavily used in shown sections

The Pico is powered from regulated +5V via VBUS or direct 5V input.

Reset line is exposed with external button.

Multiple GPIO headers (J2, J3) provide access to nearly all pins.

ETHERNET MODULE (W5500 + RJ45)
W5500 is used as hardware TCP/IP offload engine.

Connections:

• SPI interface to Pico (SCK, MOSI, MISO, CS)

• INT pin for interrupt signaling

• Powered from +3.3V

RJ45 jack with integrated magnetics (WIZ850IO style connection).

This allows:

• LAN communication 10/100/1000 (realistically W5500 is 10/100)

• Remote control, monitoring, data logging

Important note:
Stable 3.3V rail with enough current (>150mA) is required.

RS-485 COMMUNICATION (DUAL FULL DUPLEX)
Two independent RS-485 channels are implemented.

Each channel has:

• Dedicated transceiver (likely MAX485 or similar)

• Separate TX and RX lines (full duplex)

• 120Ω termination resistors

• Bias resistors (~1k range)

• Control pins for RE (Receive Enable) and DE (Driver Enable)

Important design feature:
RE and DE are controlled independently for full duplex mode.

Additional transistor stage (2N3906) used for:

• Automatic TX enable

• Optional GPIO control of transmit direction

Voltage adaptation:

• RX inputs include resistor dividers to convert +5V to +3.3V safe levels

Outputs:

• Terminal blocks for A/B differential signals

• Separate TX and RX connectors

THERMOCOUPLE MODULE
MAX31856 thermocouple interface is used.

Connections:

• SPI interface (shared or separate from W5500 depending routing)

• +5V and +3.3V rails present

• Digital pins: CS, SCK, SDO, SDI, DRDY

Purpose:

• High temperature measurement

• Suitable for industrial heating systems

Requires careful layout and shielding for noise immunity.

GPIO EXPANSION AND FILTERING
Multiple GPIO headers are exposed in grouped connectors.

Each GPIO line includes:

• Series resistor (~2k)

• RC filter (100nF capacitor)

Purpose:

• Noise filtering

• Input stabilization

• Protection against spikes

Some GPIOs are grouped as:

• 3-pin blocks (signal, VCC, GND)

• Multi-pin headers

RS-232 SERIAL PORT
Simple RS-232 interface via voltage divider.

Not a full MAX232 level converter, so:

• Likely TTL-level serial adapted slightly

• Must verify compatibility with real RS-232 devices

Connected to Pico UART pins.

MOTOR CONTROL (H-BRIDGE SECTION)
Discrete H-bridge built using MOSFETs and BJTs.

Components:

• N-MOSFETs (IRFZ44N type) for low-side switching

• P-MOSFETs (IRF5305 type) for high-side switching

• NPN/PNP transistors for gate driving

• Flyback diodes (1N4007) across motor

Control logic:

• Direction control via logic gates (74LS00 NAND)

• Start/Stop latch logic

• Manual buttons included

Features:

• Bidirectional motor control

• Protection against inductive spikes

• LED indicators for status

LOGIC CONTROL (74LS00)
Quad NAND gate used for:

• Start/Stop latch

• Direction logic

• Interlocking signals

Ensures:

• Safe switching

• No shoot-through in H-bridge

SWITCHING POWER SUPPLY (LM2596)
Main DC-DC converter section.

Components:

• LM2596 adjustable regulator

• Inductor (330uH)

• Schottky diode (1N5404 used, but not ideal choice)

• Output capacitors (220uF)

Adjustable output via potentiometer (10k).

Provides:

• Efficient conversion from 24V to lower voltages

• Main power for logic and peripherals

PROTECTION CIRCUITS
Included protections:

• Reverse polarity diodes on input

• Flyback diodes on motor

• Input filtering capacitors

• Series resistors on GPIO

• Voltage dividers for level shifting

Missing or weak areas:

• No TVS diodes on RS-485 lines

• No proper RS-232 level converter

• Linear regulators may overheat at high input voltage

CONNECTORS AND I/O
Types used:

• Terminal blocks (power, RS-485, motor)

• Pin headers (GPIO, UART, SPI)

• RJ45 Ethernet jack

• Button inputs (reset, start/stop, test)

Board is designed for:

• External wiring

• Modular expansion

• Industrial environment usage

PART LIST (MAIN COMPONENTS)

Microcontroller

• Raspberry Pi Pico (RP2040)

Ethernet

• W5500 Ethernet controller

• RJ45 connector with magnetics

RS-485

• 4x RS-485 transceivers (2 TX, 2 RX full duplex)

• 120Ω termination resistors

• 1k bias resistors

Thermocouple

• MAX31856

Power

• LM2596 adjustable regulator

• 7805 linear regulators (2x)

• Inductor ~330uH

• Diodes: 1N4007, 1N5404

Motor Driver

• IRFZ44N (N-MOSFET)

• IRF5305 (P-MOSFET)

• 2N3904 / 2N3906 transistors

• 74LS00 logic IC

Passive Components

• Capacitors: 100nF, 220uF, 470uF

• Resistors: 220Ω, 1k, 2k, 5.1k, 10k

User Interface

• LEDs (status indicators)

• Push buttons (reset, control, test)

DESIGN REVIEW SUMMARY

Strengths

• Highly integrated multifunction design

• Industrial communication support (Ethernet + RS-485)

• Full duplex RS-485 is uncommon and powerful

• Discrete H-bridge allows flexibility

• Good use of filtering and decoupling

Weak Points

• Linear regulators (7805) inefficient for 24V input

• RS-232 not properly level shifted

• RS-485 lacks surge/ESD protection

• Mixed analog/digital/motor grounds may introduce noise

• 1N5404 not ideal for switching regulator (slow diode)

Critical Recommendations

• Replace 7805 with buck converters

• Use proper Schottky diode for LM2596

• Add TVS diodes on RS-485 lines

• Separate analog ground for thermocouple

• Improve thermal considerations for power section

NEXT STEP POSSIBILITY
Next phase can include:

• PCB layout review (trace width, grounding, isolation)

• Thermal analysis

• Firmware architecture for Pico (Ethernet + RS485 + control)

• Communication protocol design

Say when ready to continue.

INDUSTRIAL OVEN / KILN CONTROLLER
This board is very suitable for temperature-controlled ovens, kilns, or reflow systems. The MAX31856 thermocouple reads high temperatures, while the H-bridge can drive fans or conveyor motors. RS-485 allows connection to remote sensors or additional heating zones. Ethernet provides remote monitoring and control. The Nextion 7-inch display acts as the main user interface for temperature graphs, setpoints, alarms, and manual control.

SMART GREENHOUSE CONTROL SYSTEM
The board can manage a greenhouse with temperature, humidity, ventilation, and irrigation. Thermocouple or other sensors monitor conditions, RS-485 connects distributed sensor nodes, and motor control drives vents or pumps. Ethernet enables remote supervision. The Nextion display shows live environment data, schedules, and manual override controls.

INDUSTRIAL MOTOR CONTROL PANEL
Designed as a local control panel for motors in conveyors, mixers, or pumps. The H-bridge allows direction and speed control, while RS-485 links to other controllers or PLC systems. Ethernet enables integration into SCADA systems. The Nextion display provides start/stop, direction, speed control, and diagnostics.

ENERGY MONITORING AND DISTRIBUTION NODE
Used in industrial or building environments to monitor power usage and control loads. RS-485 can connect energy meters, and GPIO controls relays or contactors. Ethernet sends data to a central server. The display shows consumption, trends, and alerts.

REMOTE INDUSTRIAL GATEWAY (IOT EDGE DEVICE)
Acts as a bridge between RS-485 field devices and Ethernet network. Can collect data from multiple sensors or controllers and send it to cloud or local servers. The Nextion display provides local diagnostics, device status, and manual commands.

AUTOMATED HEATING AND DRYING SYSTEM
Suitable for drying chambers, food processing, or material curing. Thermocouple ensures precise temperature control, while motors control airflow. RS-485 connects additional modules. The display allows setting drying profiles, timers, and monitoring progress.

SMART WATER PUMPING AND IRRIGATION CONTROL
Controls pumps, valves, and monitors water systems. RS-485 connects remote valve nodes or sensors. Motor control handles pump direction or flow mechanisms. Ethernet allows remote management. The Nextion display provides system overview, scheduling, and alarms.

INDUSTRIAL TEST BENCH / LAB CONTROLLER
Used for testing motors, heaters, or devices under controlled conditions. The board manages inputs, outputs, and logs data over Ethernet. RS-485 allows expansion. The display provides real-time graphs, test parameters, and result logging.

BUILDING AUTOMATION CONTROLLER
Controls HVAC subsystems, ventilation, and environmental monitoring. RS-485 connects distributed modules (sensors, dampers). Ethernet integrates into building systems. The display acts as a wall-mounted control panel.

MULTI-PROTOCOL INDUSTRIAL CONTROLLER
A general-purpose industrial controller combining Ethernet, RS-485, GPIO, and local UI. Can replace small PLC systems in custom automation. The Nextion display provides operator interface, menus, and status. Suitable for custom machines, production lines, or retrofitting older equipment.

If you want next step, I can break one of these into full system architecture (hardware + firmware + communication protocol + UI screens).