KNX introduction: a shared system for lighting, blinds and building control

[ZerOne]

What does KNX do?
KNX is a multi-manufacturer building-automation standard. Lighting is one application alongside blinds, heating/cooling, sensors and room control. A wall control can send a group message, and configured actuators respond without every function having to pass through a consumer cloud hub.

The important choice is not simply “buy a KNX switch”. Decide which communication medium and application functions your project needs. KNX TP uses a dedicated twisted-pair bus; KNX RF provides wireless devices; KNXnet/IP links installations and software through IP networking. Media couplers and routers connect the appropriate sections.

A small TP installation typically needs

• Certified KNX input devices, such as a push-button or occupancy sensor.
• A switching/dimming actuator or a KNX-to-DALI gateway matched to the lighting equipment.
• A KNX bus power supply with the required choke/decoupling, suitable bus cable and protection/enclosures.
• A supported KNX USB or IP commissioning interface and ETS software with an appropriate licence.

An ordinary DC supply is not automatically a substitute for a KNX TP supply. KNX Association's example PSU distinguishes its choked bus output from an auxiliary output: the auxiliary connection must not simply be treated as a second bus supply.

Getting started
Write down the required behaviours before selecting devices: switching, relative dimming, absolute levels, scenes and separate status feedback. Check that device application programs expose matching communication objects and datapoint types, not just matching connector labels.

A trained integrator can create the ETS project, assign individual device addresses, link communication objects to group addresses and test one function at a time. Retain the project and any security keys needed for future maintenance; they are not disposable setup files.

KNX can support local control, but the availability of a particular automation still depends on the devices/controllers implementing it. This introduction is documentation-based, not a tested project. Use an appropriately licensed electrician for Australian mains work and a suitably trained KNX professional for system design.

Official reading
KNX Association: technologies and media
KNX Association: example choked bus supply
Official KNX specification library