DALI-arduino

DALI LED Lighting Interface. Control LED Drivers with a microcontroller.

The code in qqqDali.cpp and qqqDali.h does not depend on Arduino, can be used in any C++ project by copying qqqDali_ATMega328.h and adding hardware specific code for a periodic interrupt and pin change interrupt.

Examples for Arduino ATMEGA328 included:

• Dimmer: Dims all lamps up and down
• Commissioning: Assign short addresses to lamps
• Monitor: Monitor DALI bus data

Needs a DALI hardware interface such as Mikroe DALI click. Or use this very basic DALI interface design for your experiments.

Micro-               5.6V               ___      
controller           Zener        +----|___|---- 12V Power Supply 
             ___     Diode        |     220
 RX ---+----|___|-----|>|---------+------------- DALI+
       |     10K                  |  
      +-+                         |                 
      | |100K           ___     |/   PNP             DALI BUS
      +-+        TX ---|___|----|    Transistor
       |                 1K     |\   
       |                          V
GND ---+--------------------------+------------- DALI-

NOTE: For this interface, reverse the polarity of TX in the code.

Explanation of the circuit

The DALI bus needs to be powered with a 16V (9.5V to 22.5V) power supply, current limited to 250mA. In the circuit the 220 ohm resister is the current limiter (gives approx 50 mA with 12V power supply). Using a lower current allows us to use a common 100mA PNP transistor such as BC547. A logic low is -6.5V to 6.5V, a logic high is 9.5V to 22.5V. The zener diode takes removes the 6.5V offset, and the 10K/100K resistors together with the shunt diodes in the GPIO port protect the microcontroller from overcurrent & overvoltage.

Each device on the bus should not draw more than 2mA, and the bus voltage should be at be around 10V for things to work. So every device on the bus will lower the supply voltage by 220 Ohm * 2mA = 0.5V, so this simple circuit should work with up to 4 devices on the bus.