Analog I/O module DomBus32

digitalserialRS-485

Overview
DomBus32 is a DIN-RAIL module (54 mm wide) with 3 relay outputs, 3 AC inputs and 5 programmable low-voltage I/Os. Available in two firmware/protocol variants: proprietary DomBus protocol (multi-master with DCMD commands and Domoticz plugin support) and Modbus RTU (standard master/slave protocol widely supported by building automation systems). Communicates via industrial-grade RS485 serial bus; power supply 8-25 Vdc. Optimized for extremely low power consumption (typically <10 mW, up to 150 mW with all relays ON).

Key capabilities

• 3 relay outputs (SPST) with varistor overvoltage protection, rated up to 250 Vac / 5 A (or 30 Vdc / 5 A).
• 3 AC opto-isolated inputs (100-250 Vac) to monitor presence of mains voltage on loads.
• 5 versatile low-voltage I/O ports configurable as digital inputs, counters, twinbuttons, outputs (digital, dimmer, buzzer/flash), analog inputs, SENSOR_ALARM, IN_COUNTER, etc.
• Common terminal block to share Neutral/Line or common voltage among relays and AC inputs to simplify wiring.
• RS485 bus for multi-module networks: 2 wires for data plus 2 wires for 12/24V power (shielded 4-wire cable recommended).
• DCMD feature (DomBus firmware only): module-to-module commands allowing automations to run even if the domotic controller is offline (events like PULSE, VALUE, ON, OFF, etc.).
• Extensive port configuration options (logic inversion, pull-up/pull-down, timeouts, dimmer, analog 0-10V output modes, counters with divider, sensor alarm thresholds, distance sensors, etc.).

Notes on firmware/protocols

• DomBus protocol: multi-master, low-latency, supports DCMD for commands exchanged between modules and enhanced features (recommended when using Domoticz).
• Modbus RTU protocol: standard master/slave protocol compatible with many controllers (Home Assistant, OpenHAB, Node-RED, ioBroker). Modbus supports relay timing (ON time from 31.5 ms up to many days) and standard register-based configuration.

Applications

• Switch/monitor up to 3 lights or other loads.
• Monitor appliance supply (e.g., detect presence of power to heat pump).
• Control heating zone valves and other actuators.
• Connect pushbuttons, double pushbuttons, S0 counters, PIRs, magnetic contacts, balanced alarm sensors, and more.
• Integrate existing step-by-step (impulse) light relays and expose state to domotic controllers.

Warnings

• Do not mix high voltage (230 V) loads and low voltage (5/12/24 V) loads on the same terminal block.
• Use a 4-wire shielded cable for bus and power (recommended: alarm cable with 2x0.5 mm² for 12 V power and 2x0.22 mm² for data).
• Protect 12/24 V supply with a fuse. Terminal common must be connected consistently (Neutral or Line) depending on wiring practice.
• Enable termination resistor (Rbus jumper) only on the two physical ends of each RS485 bus to reduce reflections.

Ports capabilities (summary table)
Header: Port# | Name | Capabilities | Default configuration | Description
1 | RL1 | OUT_DIGITAL, OUT_RELAY_LP | OUT_RELAY_LP | SPST relay output, 250 Vac 5 A (or 30 Vdc 5 A). Relay protected by varistor. Common terminal shared with AC inputs and relays.
2 | RL2 | OUT_DIGITAL, OUT_RELAY_LP | OUT_RELAY_LP | As RL1.
3 | RL3 | OUT_DIGITAL, OUT_RELAY_LP | OUT_RELAY_LP | As RL1.
4 | InAC1 | IN_AC, IN_COUNTER | IN_AC | 100-250 Vac opto-isolated input to sense presence of voltage. Shares common terminal.
5 | InAC2 | IN_AC, IN_COUNTER | IN_AC | 100-250 Vac opto-isolated input.
6 | InAC3 | IN_AC, IN_COUNTER | IN_AC | 100-250 Vac opto-isolated input.
7 | IO1 | IN_DIGITAL, IN_TWINBUTTON, IN_COUNTER, OUT_DIGITAL, OUT_DIMMER, OUT_BUZZER, SENSOR_ALARM | IN_DIGITAL, INVERTED | Analog/digital input or configurable output; supports counters, twinbutton mode (PU1 jumper), 10 mA output option (RO1 jumper), pullup for NTC thermistor, and balanced alarm sensors (5-state: Closed/Open/Masked/Tamper/Shorted).
8 | IO2 | IN_DIGITAL, IN_TWINBUTTON, IN_COUNTER, OUT_DIGITAL, OUT_DIMMER, OUT_BUZZER, SENSOR_ALARM | IN_DIGITAL, INVERTED | Same as IO1 with PU2 / RO2 jumpers.
9 | IO3 | IN_DIGITAL, IN_TWINBUTTON, IN_COUNTER, OUT_DIGITAL, OUT_DIMMER, OUT_BUZZER, SENSOR_ALARM | IN_DIGITAL, INVERTED | Same as IO1 with PU3 / RO3 jumpers.
10 | IO4 | IN_DIGITAL, IN_TWINBUTTON, IN_COUNTER, OUT_DIGITAL, OUT_DIMMER, OUT_BUZZER, SENSOR_ALARM | IN_DIGITAL, INVERTED | Same as IO1 with PU4 / RO4 jumpers.
11 | IO5 | IN_DIGITAL, IN_TWINBUTTON, IN_COUNTER, OUT_DIGITAL, OUT_DIMMER, OUT_BUZZER, SENSOR_ALARM | IN_DIGITAL, INVERTED | Same as IO1 with PU5 / RO5 jumpers.

Ports parameters and behavior (high-level)

• Default module address: 0xff32 (must be changed to a unique address when installing multiple modules on same bus).
• Serial bitrate and parity configurable via registers/parameters (e.g. 115200 bps default for DomBus).
• Output modes include OUT_DIGITAL, OUT_RELAY_LP (relay optimized for low power), OUT_DIMMER (0-100% in 5% steps @500 Hz), OUT_ANALOG (0-10 V), OUT_BUZZER/OUT_FLASH (configurable beep/flash patterns), OUT_BLIND (motor control with TIMEOPEN/TIMECLOSE), etc.
• IN_COUNTER supports pulse counting for energy/gas/water meters; DIVIDER option sets pulses per unit; supports TYPENAME=kWh to create energy/power devices; OPPOSITE option for import/export counters.
• IN_AC ports can be used as zero-cross detectors (on modules with AC inputs) to minimize inrush currents when switching relays.
• SENSOR_ALARM mode supports balanced double- or triple-biased alarm sensors: threshold parameters PAR1..PAR4 allow mapping of Short/Tamper/Masked/Open/Closed states.

DCMD (DomBus firmware only)
DCMD enables event-driven commands sent locally or to other DomBus modules without involving the domotic controller. Syntax: DCMD(Event:ValueLow:ValueHigh)=ModuleAddress.ModulePort:Command:Value. Supported events include OFF, ON, PULSE, PULSE1, PULSE2, PULSE4, VALUE (with thresholds). Supported commands include ON, OFF, TOGGLE, DIMMER, etc. Example usages: toggle another module output on short push, activate scene/group on long push, control heater/valve based on temperature thresholds, produce buzzer feedback on touch sensors. (Detailed configuration is available per-port in port parameters: DCMD can be set per event.).

Installation and bus recommendations (summary)

• Use linear bus topology where possible; RS485 requires two termination resistors (100–150 Ohm) at bus ends to reduce reflections. Modules provide a PCB jumper to enable termination.
• Connect cable shield to GND on one side only. All devices on bus must share the same GND reference.
• When wiring modules: connect GND first, then Vbus (12/24 V), then RS485 A and B. When disconnecting do the reverse (Vbus first, GND last).
• Recommend supplying each bus at ~13.8 V with backup battery for power outage tolerance; protect bus power with a fuse.

Included tables and configuration references
The product page provides extensive tables and examples for Modbus register addresses, DomBus parameter keywords (HWADDR, PULLUP, PULLDOWN, INVERTED, OUT modes, TIME values, TYPENAME, DIVIDER, ADDR for EVSE meters, EV-related parameters when applicable) and practical examples for Domoticz/Home Assistant/Node-RED integration. Consult the per-port configuration table for mapping Modbus registers to functions and for recommended Domoticz Description field formats.

caractéristiques / spécifications techniques

• Form factor: DIN-rail module, width 54 mm (overall dimensions listed: 53 x 89 x 65 mm).
• Relay outputs: 3 × SPST relays, 250 Vac / 5 A max (30 Vdc / 5 A), varistor overvoltage protection.
• AC inputs: 3 × opto-isolated IN_AC inputs, 100–250 Vac, share common terminal.
• I/Os: 5 × programmable low-voltage I/Os (IN/OUT, counter, twinbutton, dimmer, buzzer, SENSOR_ALARM, IN_ANALOG capability).
• Power supply: 8–25 Vdc recommended (examples use 12 V or 13.6 V nominal). Typical consumption <10 mW (0.75 mA @13.6 V); up to 150 mW (10 mA @13.6 V) with all relays ON.
• Bus: RS485 industrial-grade serial bus; standard 4-wire shielded cable (2 for power, 2 for data); default speed 115200 bps (configurable).
• Protocols: DomBus (proprietary multi-master with DCMD) or Modbus RTU (master/slave).
• Special features: DCMD inter-module commands (DomBus firmware), zero-cross detection for AC inputs (when present) to limit inrush current, support for balanced alarm sensors (5-state), configurable output monostable times from 31.25 ms up to days, analog 0–10 V output option.
• Typical use cases: lighting control (incl. step-relay systems), heating zone valves, appliance presence monitoring, integration of sensors and counters (energy/gas/water).