Peter M. Groen / DALI-Lighting-Interface

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README.md
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... ... @@ -11,20 +11,23 @@ Examples for Arduino ATMEGA328 included:
11 11 Needs a DALI hardware interface such as Mikroe DALI click. Or use this very basic DALI interface design for your experiments.
12 12  
13 13 ```
14   -Micro- 5.6V ___ DALI BUS
15   -controller Zener +----|___|---- 10-22V
16   - ___ Diode | 100
17   - RX ---|___|---|>|---+------------- DALI+
18   - 10K |
19   - ___ |/
20   - TX ---|___|-------| PNP Transistor
21   - 220 |\ 30V 250mA
22   - V
23   -GND -----------------+------------- DALI-
  14 +Micro- 5.6V ___
  15 +controller Zener +----|___|---- 12V Power Supply
  16 + ___ Diode | 220
  17 + RX ---+-|___|-------|>|----------+------------- DALI+
  18 + | 10K |
  19 + +-+ |
  20 + | |100K ___ |/ PNP DALI BUS
  21 + +-+ TX ---|___|----| Transistor
  22 + | 1K |\
  23 + | V
  24 +GND ---+--------------------------+------------- DALI-
24 25 ```
25 26 NOTE: For this interface, reverse the polarity of TX in the code.
26 27  
27 28 ### Explanation of the circuit
28 29  
29   -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 100 ohm resister acts as the current limiter. 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 resistor together with the shunt diodes in the GPIO port protect the microcontroller from overcurrent & overvoltage.
  30 +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.
  31 +
  32 +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.
30 33  
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