HomeMaster STR-3221-R1 — Smart Stair Lighting Module, 32 Steps

Tech Specs

Note: Outputs are not internally fused per channel. Use external overcurrent protection on the LED supply rails per applicable standards and installation requirements.

Installation, Environmental & Mechanical

Home Assistant / Modbus / Web Config Integration

The STR-3221-R1 supports flexible integration with:

• HomeMaster MicroPLC and MiniPLC controllers
• PLC and SCADA systems via Modbus RTU
• Home Assistant using ESPHome or Modbus integration
• Direct USB-C configuration using browser-based WebConfig tool

Configuration parameters are stored persistently in onboard flash and automatically restored at power-up.

Quick Setup Process (USB-C WebConfig)

1. Mount & Power - Mount the module on a DIN rail and connect 24 V DC.
2. Connect USB-C - Connect USB-C cable to the module.
3. Open WebConfig - Open WebConfig page in Chrome or Edge browser.
4. Connect Device - Click Connect and select the device.
5. Configure - Set Modbus address and baud rate.
6. Test I/O - Test outputs O1-O32, status LEDs and digital inputs.
7. Save & Disconnect - Save settings and disconnect USB-C.

Features:

• Driverless browser-based configuration
• Live configuration and diagnostics
• Persistent flash storage
• No external software required

WebConfig provides Modbus address, baud rate, I/O test, and channel configuration (stored persistently in flash).

uart:
  id: uart_modbus
  tx_pin: 17
  rx_pin: 16
  baud_rate: 115200
  parity: NONE
  stop_bits: 1

modbus:
  id: modbus_bus
  uart_id: uart_modbus
  turnaround_time: 100ms
  send_wait_time: 250ms

packages:
  str1:
    url: https://github.com/isystemsautomation/homemaster-dev
    ref: main
    files:
      - path: STR-3221-R1/Firmware/v0.1.0/default_str_3221_r1_plc/default_str_3221_r1_plc.yaml
        vars:
          str_prefix: "STR#1"
          str_id: str_1
          str_address: 21
    refresh: 1d

Cabling and Wirings

Power Supply

Module power (V+ / 0V): The STR-3221-R1 logic and communication operate from 24 V DC SELV/PELV only. Connect +24 V and 0 V (GND) to the terminals marked V+ and 0V.

LED power (LED PS + / -): The LED supply terminals accept 12 V or 24 V DC. Use a separate supply for the LED loads; outputs are low-side switching and require a common LED supply rail to the + group pins.

Connect + to V+ and - to 0V.

Terminal Block Layout

Top row (24Vdc | LED PS | RS-485 | DI 24Vdc | SENS.A | SENS.B | OUT O.1-O.10)

Bottom row (OUT O.11-O.32)

Ports & service interfaces

Housing notes

• Outputs are grouped in fours, each group with its own + rail - nine groups in total.
• Low-side switching: load + to the group + rail, load - to O.n.
• Two separate presence inputs SENS.A and SENS.B, each with its own + and Gnd.
• Per channel <=1.5 A (ferrite BLM31PG601SN1L). Module total <=18 A (DB128L-5.08 field terminals; choke is 24 A).

Top blocks: V+ / 0V (24 V DC module supply), LED PS +/- (12 or 24 V DC LED supply), SENS.A / SENS.B (fused 24 V sensor rails), IN1 / IN2 / GND (digital inputs). Output blocks: O1-O32 low-side outputs grouped with shared + rails. Comms block: A, B, COM (RS-485 Modbus RTU).

Front view: power, sensor rails and inputs (top); 32 outputs and RS-485 (bottom).

Output Wiring (O1-O32)

Output channels are low-side MOSFET sinks (SI2307A). Connect the LED load + to the corresponding + group rail (12 or 24 V from the LED supply) and the load - to the channel terminal (O#). Built-in SS24 flyback diodes protect against inductive switching transients. Maximum 1.5 A per channel; module total 18 A (field terminal path limit).

Digital Input Wiring (IN1, IN2)

Inputs use an ISO1212 IEC 61131-2 digital-input front-end (not galvanic isolation). Connect potential-free (dry) contacts — wall switches, push buttons, or relay / open-collector / transistor outputs that simply close DI to GND. The module supplies the wetting current from its own 24 V rail; do not feed external voltage into the input. Three-wire sensors must be powered from your own supply, with their switching output wired to the input (the module provides no sensor-supply rail). Each input has PTC fuse, TVS, and reverse protection. Do not exceed 30 V DC on input pins.

Dry-contact wiring to IN1 and IN2 (common GND).

PIR motion sensors powered from SENS rail and signaling IN1/IN2.

RS-485 / Modbus RTU

Terminal order differs across the HomeMaster range. Always read the silkscreen - do not wire by habit from another module. On this module the order is COM-B-A. Swapping A and B damages nothing but the node will not communicate. COM is required on every node.

All HomeMaster controllers and modules share the same RS-485 front end.

Bus wiring rules — apply to every device on the bus:

• One twisted pair for A/B, 120 Ω characteristic impedance.
• Run COM to every node. Required, not optional: the ports are not isolated, and COM is what bounds the common-mode voltage the transceivers see.
• Prefer one power supply for the whole bus, distributed in star topology. With separate supplies, additionally tie the 0 V references together at a single point.
• Bond the cable shield to cabinet PE at one end only. Never land a shield on A, B or COM.
• Where the bus crosses into a different electrical installation with its own earthing reference — a utility or billing meter, another building, another cabinet's PE system — fit an external galvanic RS-485 isolator at that boundary. The on-board components are transient protection, not isolation, and will not survive a sustained ground-potential difference.

Connect A, B, and COM to the bus; external 120 Ω at both bus ends.

Cable Recommendations & Shield Grounding

General Routing Rules

• Route low-level signal cables (RS-485, DI) separately from power and LED wiring.
• If crossing power cables is unavoidable, cross at 90°.
• Keep cable runs as short as practical; avoid parallel runs with high-current conductors.

RS-485 (Modbus) Cable

• Twisted pair recommended (120 Ohm characteristic impedance).
• Shielded cable recommended in industrial environments.
• Use one twisted pair for A/B and a third conductor for COM. COM must be run to every node.
• Examples: J-Y(ST)Y 2×2×0.5 mm² or LI2YCY PiMF 2×2×0.50.

Shield Grounding

• Bond cable shield(s) to cabinet PE/EMC ground at one end (PLC side recommended).
• Do not connect shields directly to signal terminals (A/B/COM).

System Architecture & Pinout

System block diagram.

RP2350 MCU and terminal pinout.

Field board layout: 32 MOSFET outputs, ISO1212 inputs, 24 V DC power rails.

MCU board layout: RP2350, TLC59208F drivers, MAX485, USB-C.

Safety and Installation Notes

• Module logic: use only SELV/PELV 24 V DC on V+ / 0V. LED supply (+ / -) can be 12 or 24 V DC.
• Install inside a control cabinet; protect wiring terminals from accidental contact.
• Each module must have its own 24 V DC supply for V+ / 0V; do not bridge GND_FUSED and logic GND externally.
• Never connect mains voltage to any terminal - this is a SELV-only product.
• Size the separate LED PS field supply and wiring for up to 1.5 A per channel (18 A module total); use appropriate fusing on the LED PS supply. Do not share LED PS with module logic V+/0V.
• Sensor rails (SENS.A / SENS.B) provide limited fused 24 V output - do not backfeed external power.
• Installation and servicing by qualified personnel only.

Compliance & Certifications

The STR-3221-R1 module is CE marked. ISYSTEMS AUTOMATION S.R.L. (HomeMaster® brand) maintains the technical documentation and a signed EU Declaration of Conformity (DoC) available for download in the Documentation section above.

• EMC Directive 2014/30/EU - EN 55032:2015 (Class B emissions), EN 55035:2017 (immunity), tested by Idvorsky Laboratories Ltd. (Job #1648)
• RoHS Directive 2011/65/EU - EN IEC 63000 technical documentation
• Low Voltage Directive 2014/35/EU - does not apply (SELV-only product, 24 V DC nominal, no mains-capable terminals)
• HomeMaster® - registered EU trademark (EUTM No. 019082911, EUIPO, registered 15 January 2025)