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DomBus36 - 12 relays DIN-rail module for home and industrial automation

DIN rail module within 12 relays, 5A 250V, supporting DomBus and Modbus RTU protocols (to be selected), for industrial automation and home automation systems, like Domoticz, Home Assistant, OpenHAB, ioBroker, Node-RED, ...
Very low power consumption, less than 750mW with all 12 relays ON.

€52.95 Save 30%
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Volume discounts

Quantity Unit discount Price You Save
1 30% €52.95 €22.69
2 32% €51.44 €48.41
3 33% €50.68 €74.88
5 34% €49.92 €128.59
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24 months warranty, easy return/refund in case of problem

Creasol DomBus36 is a din-rail relay industrial-grade module for building automations and home automation systems, 115x90x40mm, with 12 relays outputs, SPST (Normally Open outputs) with 250V 5A max capability, divided in 3 groups of 4 relays, each group with a 5-position screw terminal blocks: 1 common + 4 outputs

As other DomBus devices, DomBus36 provides excellent performance in terms of power optimization: 12mW with relays OFF, less than 750mW with all 12 relays ON! As a comparison, KMTronic 8 relays module consumes 12W, Denkovi 8 relays board consumes about 3W, Sonoff Dual R2 consumes 2W with only 2 relays enabled.

It's available with two firmware types: DomBus (proprietary protocol with enhanced features) for Domoticz controller, and Modbus RTU (standard protocol working with almost any home automation system). Check below for a detailed comparison between the two protocols.
It uses a RS485 industrial-grade serial bus, using a common shielded cable with 4 wires: 2 for 12/24V power supply, and 2 for data at 115200bps 8,n,1 (or other speed/parity in case of Modbus RTU).

It supports two different protocols (at puchase time, select the needed protocol!):

  • DomBus protocol, that is supported by Domoticz home automation controller, is a reliable multi-master protocol that permits to manage dozens of modules and get status from a module as soon as it changes. Also it includes the so-called DCMD commands that, similarly to KNX, are transmitted between DomBus modules in the same bus to activate outputs, scenes and groups in case of events without needing for the intervention of the home automation controller, useful solution to get a home automation system working even in case of domotic controller fault. Check below for an explanation about DCMD.
    The Creasol DomBus plugin have to be installed in Domoticz, using the Python Plugin Manager or downloading the software from GitHub (see the section below).
  • Modbus RTU protocol, widely used in industrial and home automation systems, is supported by almost any domotic controller like Home Assistant, OpenHAB, IObroker, Node-RED, ...
    Modbus is a master-slave protocol that permits to activate and deactivate a single relay or a group of relays by a single command. Also, it's possible to specify, for each relay, the ON time from 31.5ms to 1500 days, so the relay automatically switches OFF after the selected time.

Confused about the two versions? If you use Domoticz, DomBus version is much better because includes enhanced features like DCMD and autodiscovery.  For other building automations, Modbus version should be chosen because compatible with almost everything.
Ask for support on Telegram group https://t.me/DomBus

The RS485 serial bus is the ideal solution to get:

  • easy wiring and connection: use a common thin alarm cable within 4 wires, 2x0.5mm² wires for 12V power supply, and 2x0.22mm² wires for data. This is much easier and better than ethernet UTP/STP connections.
  • robustness differential signalling permits to connect about 30 modules with more than 200m total distance. Modules can be connected together using a mix of linear/star bus topology.
  • very low power consumption: each module is supplied at 12V and has inside an high efficiency switching mode converter to minimize the power comsumption.
  • power outage tolerant: using a 13.6V power supply with lead acid battery it's possible to supply domotic network, IPCams, NVR, switches, routers, so the system keeps working even in case of power cut-out.
  • no RF pollution, no batteries to change

For large building, to improve the bus reliability, it's possible to make more than 1 bus so in case of fault, only the bus with fault stops working.


  • available in two firmware version, DomBus suitable for Domoticz controller, and Modbus suitable for any industrial and home automation system.
  • 12 relay outputs, SPST (normally open contact on screw terminal block) with 250Vac/30Vdc 5A contact (max 30Vdc in case of DC load, 250Vac in case of AC load).
  • easy wiring: relays are divided in 3 groups, each group share a common with the 4 relays in that group.
  • each  relay block respects the creepage distance from other blocks. Do not mix high and low voltage signals inside the same block!
  • 8-35Vdc power supply (internally regulated by a switching mode power supply circuitry that minimize power consumption and dissipation).
  • low power consumption: 0.9mA @12V (12mW) stand-by current with all relays OFF, and 55mA @12V (<750mW) with all relays ON.
  • 115200 bps RS485 bus (max length: 1km), 8 bit data, no parity, 1 stop bit. Bitrate and parity may be changed in the Modbus version.
  • DCMD commands support (DomBus firmware only): this is a feature (described below) that permits to get easy automations without writing a line of code, and command exchanged between DomBus modules even in case that domotic controller is stopped. For example configuring a pushbutton input port as
    DCMD(Pulse)=11.3:Toggle, DCMD(Pulse1)=0.7:Toggle, DCMD(Pulse2)=0.8:On
    it's possible:
    * with a short 0.5s pulse, toggles on/off port #3 output of DomBus module #11
    * with a 1s pulse, toggle on/off a group of switches on the controller
    * with a 2s long pulse, activate a scene that, for example, disable all lights/loads and activate the alarm system (useful when leaving the building).


  • Relays are divided in 3 blocks: do not mix high voltage (230V) loads and low voltage (5/12/24V) loads on the same terminal block!
  • Do not use capacitive loads with high inrush current (bad power supplies, ballasts, ...) otherwise the relay contact may weld.
  • Use a 4 wires shielded cable for the bus, using two lines to send power supply (12-14Vdc) protected by a fuse.
  • To reduce noise and reflections on the bus, enable the termination resistor (shorting Rbus PCB jumper) on the two furthest ends of the bus.

More information at https://www.creasol.it/DomBus36

creDomBus36 CreasolDomBus36

Specific References


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