Open Modbus OM-16LED

A compact industrial-grade 16-channel Modbus RTU LED driver module featuring high-current MOSFET outputs, per-bank terminal grouping, wide load voltage range, DIN-rail support, and full configuration via Modbus holding registers. Designed for lighting automation, distributed I/O, and custom control applications.

1. Product Overview

The Open Modbus OM-16LED is a 16-channel low-side LED driver module intended for industrial automation, lighting control, and distributed I/O networks using Modbus RTU over RS-485. It switches DC LED loads such as LED strips, architectural lighting, and indicator arrays up to 60 VDC at up to 8 A per channel.

The module combines an STM32G474 microcontroller, eight 2EDN7534B dual-channel low-side gate drivers, and sixteen NTMFS4D0N08XT1G N-channel power MOSFETs. This architecture enables reliable, high-current, and scalable LED output control with built-in protection and per-channel MOSFET switching.

📦 Hardware Files

The full schematic and BOM are available at:

• Schematic → https://github.com/OpenModbus/OM-16LED/blob/main/assets/schematics.pdf
• BOM → https://github.com/OpenModbus/OM-16LED/blob/main/assets/bom.csv

Check the latest release for more!

2. Key Features

• 16 low-side MOSFET output channels
• Up to 8 A per channel, 60 VDC maximum load voltage
• 12 VDC direct input or 15–27 VDC via onboard converter (jumper selectable)
• RS-485 Modbus RTU communication (THVD1450 transceiver)
• Fully configurable serial parameters
• DEGSON 2EDGVC pluggable screw terminals
• DIN-rail mount using UM72S profile
• Compact PCB (100 × 72 mm)

3. Applications

Ideal for:

• LED strip lighting control
• Architectural and mood lighting
• Building automation
• PLC expansion
• Industrial signaling and indicators
• Stage and display lighting
• Custom distributed lighting networks

4. Hardware Architecture

Microcontroller

The STM32G474RETx MCU handles Modbus RTU processing, configuration storage, and output control logic. It is an ARM Cortex-M4 running at up to 170 MHz with 512 KB flash and 128 KB RAM, providing ample headroom for advanced output control features.

Gate Drivers

Eight 2EDN7534B (Infineon) dual-channel low-side gate drivers control the power MOSFETs. Their key characteristics include:

• 2 channels per IC (8 ICs → 16 channels total)
• 5 A peak gate drive current
• Precise timing and low output resistance
• Designed for reliable switching of high-current loads

Output MOSFETs

Sixteen NTMFS4D0N08XT1G (onsemi) N-channel MOSFETs perform the actual load switching. Their key characteristics include:

• 80 V drain-source breakdown voltage
• High continuous drain current
• SO8FL package

RS-485 Communication

A THVD1450 (Texas Instruments) transceiver provides differential RS-485 communication with:

• ±18 kV IEC ESD protection
• Fail-safe features
• Suitable for long cable runs

Power

The board supports two input modes selected by an onboard jumper:

• 15–27 VDC input — passes through the R-78E12-1.0 step-down regulator (RECOM), which generates the 12 V gate driver supply
• 12 VDC direct input — bypasses the 12 V converter; 12 V is fed directly to the gate drivers

In both modes the R-78E3.3-0.5 step-down regulator (RECOM) generates 3.3 V for the MCU and logic from the main input rail.

5. Electrical Specifications

Supply

• 12 VDC direct input (jumper: bypass mode) or 15–27 VDC input (jumper: converter mode)
• Internal regulated 12 V gate drive supply (converter mode only)
• Internal regulated 3.3 V logic supply

Outputs

• 16 low-side MOSFET channels
• Up to 60 VDC load voltage
• 80 VDC absolute maximum
• 8 A max per channel
• Channels grouped into 4 banks of 4

Communication

• RS-485, 2-wire
• Modbus RTU protocol
• Default settings: 9600 baud, 8N1, address 1
• All communication parameters can be reconfigured via holding registers

6. Mechanical Information

• PCB: 100 × 72 mm
• DIN-rail enclosure compatibility: UM72S profile
• DEGSON 2EDGVC pluggable screw terminals
• Mounting suitable for industrial control cabinets

7. Functional Overview

Each output channel is controlled by a per-channel duty cycle value stored in a holding register. The MCU generates a PWM signal accordingly, driving the gate driver and MOSFET to regulate LED brightness. A duty cycle of 0 turns the channel fully off; the maximum value drives it fully on.

8. Modbus Interface

Supported Function Codes

To be announced soon.

Holding Registers

Configuration registers start at 0x00 and are stored in non-volatile memory.

Register Address (Hex)	Name	Description	Allowed Values	Default
0 (0x00)	Slave Address	Modbus device ID	1–247	1
1 (0x01)	Baud Rate Code	Serial speed selector: 0=1200, 1=2400, 2=4800, 3=9600, 4=19200, 5=38400, 6=57600, 7=115200	0–7	3
2 (0x02)	Parity	Communication parity	0=None, 1=Even, 2=Odd	0
3 (0x03)	Data Bits	Serial data width	5–9 (typ. 8)	8
4 (0x04)	Stop Bits	Serial stop bits	1–2	1

Example Modbus Commands

To be announced soon.

9. Wiring

The OM-16LED uses low-side (MOSFET) switching. The module connects the LED load to ground when ON; the load must be powered from your external power supply.

The 16 outputs are grouped into four banks of 4 channels (Bank A–D). This allows one board to drive LED loads powered from different voltages simultaneously.

Examples:

• Bank A → 12 V LED strips
• Bank B → 24 V LED strips
• Bank C → 48 V LED channels
• Bank D → 5 V LED indicators

Low-Side Output Principle

Each output contains a power MOSFET that sinks current:

Load +V  ─────── LED Load ─────── OUTx (SINK)
                                       │
                                       └── GND (OM-16LED)

Recommended Wiring Steps

• Connect the load voltage (up to 60 VDC) to the Vx terminal of the bank.
• Connect the output pin (OUTx) to the negative side of the LED load.
• Tie power supply GND to OM-16LED GND.
• Ensure the supply can support the total current of that bank.

⚠️ Important Grounding Requirement: All load power supplies must share a common ground with the OM-16LED. This is required for the low-side drivers and internal logic to reference the same electrical 0 V.

10. Safety Notes

• Do not exceed 60 VDC load voltage
• Ensure load currents stay within 8 A per channel
• Maintain proper RS-485 termination and shielding
• Verify adequate heat dissipation when operating at high currents

11. Contact & Support

For questions, feedback, or technical assistance regarding the Open Modbus OM-16LED, the following support channels are available:

📧 Email Support

For general inquiries, firmware questions, or troubleshooting: [email protected]

🛠 GitHub Repository

Issue tracker, source code, hardware design files, and community contributions: https://github.com/OpenModbus/OM-16LED

💬 Open Modbus Discussions

Share projects, ask for help, or suggest features: https://github.com/orgs/OpenModbus/discussions

📝 Bug Reports & Feature Requests

Submit issues directly via GitHub Issues: https://github.com/OpenModbus/OM-16LED/issues