Practical Issues Regarding DALI System Wiring

Practical Issues Regarding DALI System Wiring
The Guide to Lighting Control Systems for Home Automation

Which Cabel Do I Need For DALI?

In terms of wire materials, it is not required to use professional shielded wires such as 485 or KNX, only ordinary power cable is OK. According to the DALI bus standard, each DALI bus can connect 64 devices, which can be controlled by one main-controller.Broadcast, group or single addressing possible.

The frame of the main unit consists of 19 bits and communication speed  is 1200 bit/s; The voltage range of logic level 0 is -6.5V-6.5V, and the voltage range of logic '1' is 9.5-22.5V. This wide voltage range makes DALI have low requirements for wire materials, and DALI lines do not require the special wiring such as twisted pairs or special cables. Existing control lines used in installation can also be used as DALI lines.

What is the maximun length of DALI Cable?

DALI bus maximum transmission distance: According to different wire conductor materials and diameters, copper wire, 1.5mm2 specifications, ensure that the maximum voltage drop cannot exceed 2V, and the maximum transmission distance can reach 300 meters. Aluminum wire, 2.5mm2 specification, with a maximum transmission distance of 300 meters. In addition, the impact of working temperature should also be considered. If the working temperature reaches 75 ° C, the maximum transmission distance of copper wire will be reduced to 281m, while that of aluminum wire will be reduced to 288m.

If it exceeds 300m, add a DALI relay to amplify the signal on the DALI bus. The wire material, wire diameter, and temperature will have an impact on the transmission of the entire signal. According to the DALI bus standard, the copper wire is between 1.5 square meters and 2 square meters. Regardless of the temperature, it meets a requirement for DALI signal line transmission. Therefore, we prefer a 1.5 square meter to 2 square meter power line as the DALI signal line. That's also a 1.5-2 square meter copper wire, divided into soft wire and hard wire. Multiple stranded flexible wires are used for household and single stranded wires are used for outdoor or construction sites.

Soft wires have advantages in heat dissipation, conductivity, and tensile strength. When using hard wire to thread the tube, it is easy to break.

Hard wire has good antioxidant performance and long service life; However, during construction, if the circuit turns too much, multiple strands (flexible wires) are easier to wear.

If there are many branches in the DALI system wiring, how should the maximum transmission distance be determined?

It is determined by the line length between the two devices with the farthest wiring distance on the bus. Assuming our house is a square, the square of the largest side is the square of the length and the square of the width. Based on the length and width of the house, we can evaluate whether the maximum edge exceeds 300m. It is also crucial to evaluate whether the DALI main power supply is placed in the middle or on the side.

Why there is no problem  when total wiring distance exceed 300 meters or is there any hidden danger?

It is entirely possible that the standard answer is the most conservative. What does it mean? As long as you follow the standard length and cable requirements for wiring, and use DALI certified products, there will definitely be no problem. If not, it depends on the design margin and consistency of the bus product, and there is uncertainty about whether it can work. So, whenever possible, wiring design should be based on standards.

If the material and specifications of the wire are not fully considered during actual engineering wiring, and the length exceeds the standard, is there a solution?

If the wiring can't be rerouted, one good remedy is to reduce the maximum output current of the wiring power supply. You can consider replacing the independent bus power supply or contacting the device manufacturer to change hardware parameters. It should be noted that if the wiring is too long, the parasitic capacitance, parasitic inductance and other Confounding in the wiring system will have a greater impact on the transmission signal waveform, which is likely to affect the stability of the entire DALI Photosystem. Therefore. At the beginning of the entire system wiring, we recommend not exceeding 300 meters according to DALI's relevant wiring requirements, as exceeding 300 meters will affect the stable operation of the system.