KNX vs Dali vs DMX Lighting Protocol

When it comes to choosing a lighting protocol for designing a Lighting Control System (LCS) we are often left confused on which is the best, reliable, scalable, feature rich, future ready and cost effective protocol. To start with based on above parameters we have narrowed down this discussion to three widely used protocols in the lighting industry which are (a) KNX (b) DMX and (c) Dali. All three protocols are scalable and were developed between years1990 - 99 for different application in lighting industry for the purpose for automation.


 

KNX Protocol

Building automation protocol


KNX protocol is developed by KNX association with the aim of integrating & controlling multiple systems such as heating system, lighting system and access control systems in a building through central computer. More than 500 manufacturers around the world have developed KNX based devices across HVAC industry, Lighting industry and Security industry. Since with a KNX based systems there is a guaranteed forward and backward compatibility of products on the existing bus network, it becomes easy for the system designer to choose quality based devices or replace them with devices from other manufacturers in case devices are defective by design or run out of stock.


KNX System Architecture


System Overview


KNX is a decentralised system i.e. if one device stops working, the rest will continue to function unhindered. KNX is a wired system in which all KNX devices are connected to the KNX Bus Line. KNX systems consist of 5 components i.e (a) KNX Power supply (b) KNX Bus Line (c) Actuators (d) Sensors (e) IP Interface


(a) Power supply

This is a special KNX power supply unit that powers the KNX Bus Line so as to maintain a reliable connection between all devices.

(b) KNX Bus Line

Most simplest form of KNX Bus Line is Twisted Pair (TP) or 2 core cable. In KNX TP the bus cable supplies all bus devices with both data and power.

(c) Sensors

These are human interface devices such as switches, rotary dimmers, touch pads, thermostat touch panel, fingerprint scanner etc. which take input from direct human interaction and pass this message to the Actuators via KNX Bus Line.

(d) Actuators

Actuators are KNX controllers which are connected to KNX Bus Line and Appliances. They are responsible for controlling the functioning of connected appliances such as lights, fans, AC, projector, blinds etc.

(e) IP Interface

It is a KNX device that is connected to your WiFi router and KNX Bus Line. Through this device KNX system integrators program all Sensors and Actuators via ETS software.


Demerits

  1. Special KNX licensed system integrators are required to install and program the system via ETS KNX proprietary software. So any time you need to change configuration or if any device is replaced then you will have to call the KNX system integrator.

  2. KNX does not provide integration with Home automation standards such as Apple HomeKit, Google Home or Amazon Alexa. Third party services needs to be used.


 

Dali Protocol

Home lighting protocol


Dali is successor to 1-10v drivers for residential and small scale commercial lighting, it is the most widely used wired home lighting protocol. Dali main function is to group lights, dim the brightness and tune the colour of lights upto 2 channels. Dali had interoperability issues between devices of different manufactures, but Dali-2 has solved this problem where every manufacturer has to certify his device via a third party test laboratory to use Dali-2 logo on devices, again all Dali devices can be operated with Dali-2 devices.


Dali System Architecture

System Overview


Dali is a semi centralised system i.e. if one device stops working, the rest will continue to function unhindered, but still the complete system depends on Dali Controller. Dali is a wired system in which all below Dali devices are connected to the Dali Bus Line, similar to KNX. Dali systems consist of 5 components i.e (a) Dali Power Supply (b) Dali Line (c) Dali Controller/Bus (d) Ballast (e) Sensors


(a) Dali Power Supply

It powers the Dali Line so as to facilitate communication between Ballast, Sensors and Dali Controller.

(b) Dali Line

Dali Bus line is a 4 or 5 core cable (Line, neutral, earth optional and two control wires). A DALI line can be connected to a maximum of 64 DALI type Ballast. Dali control wires can be used along with mains line without any signal interference.

(c) Dali Controller / Bus

Dali controller is like device which can program the Dali Ballast via usb or IP interface or directly via a touch panel.

(d) Ballast

Dali ballast are devices or appliances controllers which control the power and functioning of the appliances such as bulbs, down lights etc.

(e) Sensors

These are human interface devices such as switches, rotary dimmers, touch pads and scene controllers which take input from direct human interaction and pass this message to the Dali Controller.


Demerits

  1. Dali has single point of failure i.e. if the Dali Controller / Bus fails then all Ballast and Sensor connected to it will stop working

  2. As Dali is an open source protocol it can be manufactured without any certification, hence they are difficult to commission.


 

DMX Protocol

Lighting & Effects protocol


DMX512 is the most famous, robust and widely used lighting and effects protocol in the market. Manufacturers can produce devices based on this open source protocol without getting any kind of certification. Originally developed for stage lighting and control, with advent of Artnet it has now moved to interior architectural, billboards, stadium and concerts lighting.


DMX512 System Architecture