Creasol DomBus31: 8 relays module for home automation system, with very low power consumption

Creasol DomBus31 is a din-rail relay module, 115x90x40mm, with 8 relays outputs. 6 relays are SPST (Normally Open outputs) with 250V 5A max capability, and 2 relays are SPDT (Normally Open and Normally Closed outputs) with 10A capability. It can be connected to the Domoticz controller by a RS485 serial bus (4 wires, 2 for 12/24V power supply, and 2 for data at 115200bps).

As other DomBus devices, DomBus31 provides excellent performance in terms of power optimization: with all 8 relays active (the worst case), the power consumption is only 500mW! 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.

Suitable to be used as Domoticz relays module: using a simple 4 wire shielded cable it's possible to supply and interconnect up to 30 modules like this, through RS485 ModBus protocol already implemented in Domoticz (a plugin must be installed): RS485 is a strong communication system, easier to be connected than ethernet, with no RF pollution, and already includes 12/24V power supply in the bus cable.

Features

• 6 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).
• 2 relay outputs, SPDT (normally open and normally closed contacts on screw terminal block) with 250V 10A contacts.
• Relays are divided in 3 blocks, each 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: 0.75mA @12V (9mW) stand-by current with all relays OFF, and 41mA @12V (500mW) with all relays ON.
• 115200 bps RS485 bus (max length: 1km).

DomBus31 Ports capabilities

Default address: 0xff31

(1): can be used as BLIND output, to open a blind/curtain, but only the previous port can be configured in Domoticz as OUT_BLIND because, when configured as OUT_BLIND, DomBus device automatically configure the next port to drive a relay in open direction.

Application notes

Heating/ventilation system

The following simple diagrams represents the connection to a heat pump (controlled by low voltage signals), a ventilation system (controlled by low voltage signals) and a 3-vias valve (supplied by 230Vac).

With Domoticz it's easy to get heating/cooling system with heat pump, optimized to consume most energy from photovoltaic, and a air renewable controlled mechanical ventilation with chiller and coil that regulates the relative humidity to get the maximum comfort.

For security reasons, do not mix high and low voltage loads in the same block! For example it's not safe to connect, on Block3, a 230V valve to RL8 and a 12/24V valve to RL7! On each relay block it is possible to use only low voltage or only high voltage loads.

ADSL router controlled by Domoticz script to prevent hang-up

The following schema shows how to use the normally-closed contact of SPDT relay to supply a router.
A script will check that internet is working, and in case of failure activate the reset to turn power supply OFF for 10 seconds, resetting the router.

MORE INFORMATION AT https://www.creasol.it/CreasolDomBus31