Low level integration made easy
Why integrate systems in the home together? What is the advantage to the home owner in having the lighting system, the security system and the air conditioning system all integrated together? Integrating systems should ultimately provide simplification for the home owner, with common control devices and user interfaces for all systems, rather than separate control devices with different user interfaces for each system that don’t talk to each other.
Providing basic integration between systems can be relatively straightforward.
Integration between control systems and devices can be split into two different types, ‘high level integration’ and ‘low level integration’. High level integration involves systems/devices interacting with each other at a communication or ‘protocol’ level. They both talk the same language and use this language to understand control information, status information and other data. Low level integration is a more basic, but still effective, way for systems and devices to communicate and involves a contact being closed (usually a relay) to pass information from one system to another.
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This article focuses on low level integration; high level integration will be featured in a future edition of Connected Home.
Low level integration using a voltage-free (or ‘dry’) relay contact in one system to send basic information to a digital input in another is a simple but effective way of integrating systems together. For example, dry contacts and digital inputs in C-Bus can be used to send and receive information for air conditioning zone dampers, irrigation solenoids, rain sensors, security systems, access systems and blind/shutter systems. Some examples of low level integration are provided below.
Air conditioner control
When a reverse cycle, ducted air conditioning system is installed, normally there are a number of switches installed to individually switch the zone dampers on or off. These conventional wall switches are usually located in a central location alongside a thermostat.
Integrating the zone dampers into a home control system is usually relatively straightforward. The manual switches are typically a change-over type switch that feature a common connection and, depending on the switch position, drive the damper motor to either the open or the closed position.
The manual wall switch for each zone can be replaced by a change-over relay, controlled by the home control system. The change-over relay (like the switch) should have a common connection and two contact positions, i.e. ‘Normally Open’ and ‘Normally Closed’. This refers to the position of the relay contact when it is not energised.
By replacing the manual switch with a control system relay, it is possible to control the air conditioning zone damper from any device connected to the control system – a C-Bus Dynamic Labelling Technology (DLT) switch, for example. Note that while air conditioning damper motors can be rated at mains voltage or extra low voltage (ELV), they are more commonly ELV, with most being 24V AC.
Many air conditioning systems provide low level integration information as to whether the air conditioner is running or not. The air conditioner will close a relay contact when running, which can then be connected to a C-Bus bus-coupler or auxiliary input unit so that the state of the air conditioner is known by the home control system.
Irrigation control
A simple contact closure can be used to switch power to irrigation solenoids.
Irrigation solenoids are inductive loads and therefore need a special relay contact rating for control. The C-Bus SELV relay unit has been designed with this in mind. Each contact is rated at 2A and is suited to withstand the conditions associated with switching inductive loads. This unit is powered from C-Bus and each of the eight independent relays has a single pole, change-over contact with local manual overrides for testing the watering zone when setting up the system.
The unit also includes a ‘fail to off’ feature. This feature de-energises all of the contacts upon power failure. This ensures the zone solenoid doesn’t switch back on when power is restored as the ‘off’ command may have occurred when the power was off. The zone can be re-energised under program control if required.
Irrigation systems often have a rain sensor to feedback that no watering is required. While the method of detection differs vastly, most rain sensors have a simple dry contact that can be connected to a bus coupler.
Security interface
Many residential security panels have the capability to integrate with control systems through relay contacts. The state of an alarm panel (for example, armed or disarmed) can be communicated to a control system by relay contact closures. A relay in the security panel can be connected to a bus coupler or auxiliary input unit. Once the control system knows the state of the security panel, this information can be displayed on a touch screen and used to trigger scenes or schedules. Likewise, a dry contact closure from the control system can be linked to the security system to initiate arming. This enables a home control system wall switch to send an ‘Arm Security System’ signal to the alarm panel.
Blind control
Not all blind/shutter control involves controlling the blind motor directly. There are a number of blind systems that include the ability for contact closure inputs from another system to provide control of the blinds. A typical example is a blind system with a ‘common’ connection, an ‘up’ connection and a ‘down’ connection. When a relay contact is connected between the ‘common’ and ‘up’ connections and the contact is pulsed on-off, the blind will go up until it reaches its uppermost position. Likewise, if a contact is placed between the ‘common’ and the ‘down’ connections of the relay and pulsed, the blind will go down until it reaches its lowermost position.
If the blind is in the process of going up or down and both contacts (up and down) are activated simultaneously, the blind will stop.
Energy meter integration
There are a number of products on the market that offer low level integration of power metering. The pulse power meters make a momentary contact closure when a certain amount of power has been used. Taking the information from such devices and feeding it in to C-Bus through a bus coupler or auxiliary input unit gives the system the ability to display power use on a colour touch screen or PC.
Conclusion
Integrating a home control system to other systems and devices can be simpler than you think. If you are an electrical contractor who has installed a C-Bus system, then integrating other systems using low level integration methods may not be quite be the jump you might imagine it to be. If you are an established systems integrator, the new SELV relay unit may be the product you were looking for to make low level system integration with C-Bus more flexible and affordable.
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